Latin motto

[John Davis]

Can you classicists out there help a poor engineer with the translation of
the motto which I recently came across on a 17th or 18th century stained
glass dial?  It reads:

SIC VITA NVLLA DIES SINE LINEA

I think that's the right word order but it's just possible that LINEA,
comes before the DIES SINE  - it's written on a banner.

Thanks,

John Davis
N52 5m
E1 3m

Re: plotting timelines for giant sundials

[John Davis]

John,

I currently have a similar problem of helping to delineate a large dial,
this time a vertical decliner with a 17 foot gnomon which is to be carved
directly into the wall of a tower.  Needless to say, the wall is not
absolutely flat.

My current solution has been to build a laser trigon which will be mounted
directly on the real gnomon.  The protractor of the trigon is 300 mm in
diameter.  It has a ring of holes at 1.25 degree intervals, which
corresponds to 5 minute intervals on the dial face.  The laser assembly
locates with a pin into this ring.  The pin passes though a sliding vernier,
which has 5 holes set at 0.25 degree intervals, thus allowing the individual
minutes to be displayed on the dial.  The precision required was achieved by
drilling the holes in the protractor using an accurate rotary table clamped
to the pillar drill.

The alignment of the gnomon to be truely polar pointing is more difficult
than drawing the hourlines - as the wall isn't guaranteed flat, there is no
point of reference and its presence prevent you looking up the gnomon at the
pole.  My solution here is to mount a laser looking down (and parallel to)
the gnomon.  The laser beam hits a mirror stategically placed just below the
gnomon.  The mirror (first surface, optically flat) is aligned to be
parallel to the equator by means of a theodolite.  This theodolite is
co-mounted with the laser and looks at the sun though a suitable filter.
Its co-ordinates are set to values of the sun's instantaneous Declination
and Local Hour Angle, obtained from a portable computer.  When the gnomon is
properly aligned, the laser beam reflects off the mirror and retraces its
path to the laser, which is fitted with a surrounding screen to show the
laser spot when it is slightly in misalignment.

That's the theory - the proof will come next month!  Any other suggestions
welcomed.

John Davis

Re: Heliograph

[John Davis]

I am lucky enough to own a heliograph, having recently bought it from
another BSS member.  It dates from WW1, and looks just like the one in Peter
Mayer's jpeg with the exception that the sighting vane is more complex, with
a set of cross wires and a fold-down vane on which the dark spot from an
unsilvered spot in the centre of the mirror is aligned.

  It's described as a Mk5, and comes with its own mahogony tripod and set of
spares etc.  There is a range of attachments (most in very solid brass)
included in the leather carrying bag.  One of these is a duplex mirror, used
when the sun and the receiving station are in opposite directions.  This
mirror, which fits on the arm were the sighting vane is in the jpeg, is
always used to direct the sun onto the main signalling mirror when the sum
of the angles of incidence and reflection is 90 degrees or more.  The main
mirror has a slow motion screw so that the operator can track the sun during
long messages.

I have full instructions on how to set up and use, but they run to several
pages so I won't reproduce them unless anyone contacts me directly.

The accompanying book (The Heliograph - A short history by Alan Harfield,
pub Royal Signals Museum, 1981, ISBN 0950121835) describe achieving signal
ranges of up to 53 miles with a 5 inch mirror (like mine), and up to 83
miles to 9 and 12 mirrors.  This was done in the mountains in northern
India.  Heliographs were also much used in the States, for example by
General Miles in 1878/9, and there are various quotes from Geronimo, who
believed the flashes were spirits!

All I need to do now is find someone else with a heliograph, and then we can
have aconversation (after I've learned Morse!)

Regards,

John Davis

Re: A Tough One?

[John Davis]

Mike,

I encountered a similar problem in analysing the stained glass dial from
Wendon Lofts.

Assuming that there are no signs of the gnomon support to define the
sub-style angle on your dial, I would get a value of the declination from
the asymmetry of the earliest and latest hour lines on the dial.

Then, having measured all the hour (and half- and quarter-hours if they
exist), I would plot y = hourline angle - LHA vs x = LHA.  This should give
a curve which starts at the origin, rises to a peak, then returns to zero at
LHA = 90 degrees (this for the case of a direct south dial - the curve will
be offset for the am and pm halves for a decliner).  This experimental plot
can then be compared to a series of theoretical ones calculated for
different latitudes eg by the BSS Sundial Constructor program.  The closest
fit tells you the latitude of your dial.

The advantage of the rather strange-looking x-y parameters that I have
suggested is that it (a) it makes use of all the hour line information you
have, (b) it is most sensitive to lines around 45 degrees, and (c) plotting
the difference between hourline angle and LHA maximises the differences
between curves for different latitudes.

You may have to iterate around the above loop a couple of times if there is
significant uncertainty as to the declination.

I hope this helps - I have the Excel plots from the Wendon Lofts dial if
they are of any use.

John Davis

Re: Laser Trigon

[John Davis]

Hi Alexei,

I have built a lightweight laser trigon from a laser pointer and some
scraps of perspex.  As well as producing hour lines and declination lines on
arbritrary surfaces, the trigon also has an attachment that allows it to
project analemmas about any hour line.

I have written up the instrument, and am expecting the article to appear in
the next (October) issue of the British Sundial Society Bulletin.

I supplied some pictures of the instrument to Bob Terwilliger, which he said
he may add to his own version on his web pages:

http//www.shadow.net/~bobt/trigon/trigon.htm

Regards,

John Davis

Re: More on Metal Sundial Processes

[John Davis]

Tony,

Great stuff! Can you give any indication of how much currect is needed (per
square inch of object?).

Also, have you ever tried masking some areas of the film ( hour numbers)
before the dying process, so that they come out a contrasting (or clear)
colour?

Cheers,

John

-
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

Re: Making Metal Sundials II

[John Davis]

This is real cookery!  As an alternative to etching face down in a flat
dish, it is simple to use a vertical tank as supplied for etching PC boards.
These are tall and very thin - about 1.5 cm wide, and big enough to take the
plate that is being etched.  Easy to make with two sheets of perspex spaced
apart and sealed with silicone.  Agitation is provided by a steady stream of
air supplied to a perforated tube in the bottom of the tank by an aquarium
pump.  A heater, again of the sort to stop your tropical fish freezing, gets
the ferric chloride to a usable 40C.

The key is to get a good quality photoresist that doesn't fail - the aerosol
type has a very limited shelf-life, I've found.

Cheers,

John
--

Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

A Sundial Glossary

[John Davis]

Dear Dialling Colleagues,

The British Sundial Society (BSS) has decided that a Glossary of dialling
terms would be a good idea.  It would have two main purposes:

- to provide a refererence source for newcomers to dialling, and

- to try to set preferred definitions of the terms, symbols and descriptions
which we all tend to use rather loosely.

I  volunteered to edit such a document, and have now produced a version
which is ready for review.  Although the document is aimed mainly at BSS
members (who live world-wide, of course) and thus concentrates on British
oriented aspects, it is hoped that it will be of use wherever diallists use
the English language.  It is also expected that the Glossary will be useful
alongside the NASS FAQ project, when that is ready.

As well as a dictionary section, the document contains a preferred set of
mathematical symbols, some contentious sign conventions, and a brief
chronology of dialling.

The Glossary has been written in a form which will be printed for BSS
members.  It is also hoped that it will be put on the BSS web pages in the
future, after BSS members have debated its contents and agreed on correct
definitions.  In the meantime, it can be viewed on my rudimentary web site
at:

www.btinternet.com/~john.davis

I'd welcome any feedback, and am quite willing to be over-ruled on choices
of symbols etc, if there is a general consensus.

PS - Netscape users will see some odd formatting - blame Bill Gates, because
it was converted from Word97 and is fine in MS Explorer!

Over to you!

John

--
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

Anodised Sundials

[John Davis]

Hi Tony (Moss),

Just thought I'd let you know that I'm underway with some anodising
experiments (better than Xmas shopping, anyway!).

By following your instructions, I've succeeded in getting a nice yellow
finish on a 10x10cm square of aluminium.  It's clearly an alloy of some
sort, but I don't know its origin.  I was limited by the fact that it was
pulling 6 amps at only 8V - the max current of my homemade power supply and
the output transistor was getting too hot to touch, so I ended the run after
only 15 minutes.  By halving the size of the cathode (originally 2 pieces
150 x 150 mm of aly alloy, one on either side of my icecream tub bath, I've
got the current down to 3 1/2 amps and the voltage up to 14 V, so this
should be better.  I know where I can lay my hands on a 40 A regulated
supply that I made for someone years ago, so I shouldn't be limited there in
the long run.

Ony partial success on the masking front so far.  I've made your spray paint
technique work but I'm limited in the shapes I can produce in it to lines
and simple masking tape cut-outs.  Etch-resist pen applied after the caustic
soda step floated off after a couple of minutes in the sulphuric acid, so
I'll need to keep experimenting.

You weren't kidding when you said you need good ventilation, were you!

Thanks for your guidance - hours of endless fun to come before I get to an
actual dial, I think.

Best regards,

John

--

Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

Re: Solstice Perigee

[John Davis]

Roger,

I'm not sure of the exact time of Full Moon, but according to my Psion the
declination at midnight will be 19deg26min.

I hope that helps!

John


Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

Transalpine hours

[John Davis]

Hi all,

I've come across a reference to "transalpine hours" in 
Heilbron's excellent "The Sun in the Church" (pg 66). This is a term which 
escaped me when I was compiling the BSS Glossary. Can someone supply a 
definition, please.

Regards,

John
---
Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

Re: shadow velocity shadow tracing

[John Davis]

John Carmichael wrote (replying to Chris Lusby Taylor):

You're right!  I realized as soon as I sent my message that a small
diameter
floodlight with a wide beam would be better than a tight beam, because it
must illuminate the entire style and not just a portion of it.


A drawback with the floodlight scheme is that a very tall ladder will be
needed unless you are only going to make use of the small bit of the gnomon
near the origin.  I know to my cost that big gnomons rarely have the
small-scale accuracy required!

 Since what you are actually trying to do is to reproduce the method of a
trigon (as Chris pointed out), why not use a real laser trigon.  Bob
Terwilliger has one on his webpages at
http://www.shadow.net/~bobt/trigon/trigon.htm (based on a transit
mechanism), and I published a cheap-and-cheerful small version in the BSS
Bulletin October 99.

Once the trigon is fixed to the style, and the hour angle set using the
incorporated auxilliary dial, all you have to do is swing the laser on its
declination axis and the spot will follow the humps and bumps on the ground
precisely.  If done at night, the laser spot is easy to see.  If done in
bright sunshine, you might need a red specular-reflector target and some red
sunglasses to see the laser spot clearly.

It's a shame you are so far away, as I built a big version of my trigon
for the New Hall Oxford dial, but it didn't get fully used and I'm looking
for another application!.  By indexing the auxillary dial with 0.25 degree
intervals, it gives 1 minute of time resolution.


Regards,

John


Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

Re: Azimutha Sundial (once more)

[John Davis]

Hi all,

I've been watching this thread with interest, and have been honoured that
the draft Sundial Glossary which I'm editing for the BSS has been quoted a
few times for the definitions.  I should say, though, that these definitions
are not yet definitive(!) and I am still working to refine them to be as
useful as possible.

I think Gianni's definitions are very helpful, and will be looking to make
sure the next draft of the Glossary takes his points into account.  In
particular:

*  a true azimuthal dial must have a vertical style.

*  a horizontal dial merely has a horizontal dial plate.  One version  - the
most common - has a polar style and the shadow position is given by the Hour
Angle (although the marked scale can be calculated for times other than LAT,
e.g. the longitude correction can be built in).

*  the Singleton dial (not a formal entry in the Glossary) is a hybrid
horizontal with a large number of scales for different dates, allowing Mean
Time to be indicated.

*  horizontal dials with styles at arbitrary angles (and an inbuilt date
scale) are what Gianni calls mono-filar.   This is not too bad a term, but
I am looking for an alternative as it implies that the gnomon (and not just
the style) is a thread - as it is in the related bifilar dial.  Any
suggestions?

Since the experts of the list continue to come up with so many variations on
the sundial theme, it seems not to be helpful to invent terms for all
possible variants.  Thus, for dials other than common horizontal, decliners,
analemmatic etc etc, I prefer just to describe the key elements, viz.:

* dial plane orientation
* style orientation
* time (and date) scale(s) used.

I'll now disappear into the background again and watch developments!

Happy dialling,

John

Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: Gianni Ferrari [EMAIL PROTECTED]
To: Sundial List sundial@rrz.uni-koeln.de
Sent: 25 February 2000 14:18
Subject: Azimutha Sundial (once more)


 Hi all,

 I have read with a lot of interest the numerous messages dealing with  the
 azimuthal sundials and I have noticed that sometime there is a little
 confusion on the names that we use for the different  types of sundials.
 I write you my opinion.

 In the sundials the time is pointed out from the shadow or of a point
 (nodus) or of a curve (generally a rectilinear style). The calculation of
 the position of this shadow depends - except rare cases - from the two
 coordinates that determine the position of the Sun in the sky : hour angle
 and declination of the Sun (equatorial coordinates) or Azimuth and Height
 (local coordinates).
 Moreover obviously the Latitude and Longitude of the place.

 If we want that the position of the shadow depends only on one of the
 coordinates we have to consider as element that casts the shadow a
 rectilinear style whose shadow intersects a set of date  lines that we can
 trace as we want on the dial
 .
 In an azimuthal sundial the only coordinate that we want employ is the
 azimuth of the Sun.
 Since the azimuth is the angle that the vertical plane containing  the Sun
 makes with the meridian plane (and therefore it is the angle between
planes
 all passing through the vertical line of the place) the only style that is
 possible to use for having a REAL azimuthal sundial is a vertical style.
 The Azimuth is given by the angle that the shadow of this vertical style
 forms with the line N-S

 If the plane is horizontal we have the several sundials that Fer de Vries
 has shown with concentric circles as date line ;
  if the plane is vertical it is opportune (but not necessary) to take the
 date lines horizontal; etc.
 A really azimuthal sundial can be obviously built also on a tilted plane
 (the style always vertical ! )
 The well known Analemmatic Sundial is an Azimuthal S.

 In the same way  if we want that the position of the shadow depends only
on
 the hour angle we have to take a polar style,  that is a style parallel to
 the straight line through which all the hour planes pass : all the
sundials
 with Apparent Time with polar style are so.

 In similar  way we can build sundials in which the position of the shadow
 depends only on  the Meridian angle  or on  the Vertical angle  (see
the
 Ptolemaic Coordinates in The Compendium,  March 1999). In this cases the
 style would have to be horizontal in direction E-W and in direction N-S.

 In all the other cases (for ex. Horizontal plane  with tilted style,
 vertical plane  with horizontal style, etc.) the position of the shadow
 doesn't depends only on one  coordinate (Azimuth) but also from the Height
 of
 the Sun : for this  reason they cannot be called strictly azimuthal.

 Since I could not call azimuthal these solar clocks (because they don't
have
 this characteristic  even if their shape  look like  azimuthal) I have
 called them (in my program with which them  can be calculated) Monofilar
 since the shadow  is made  only from one style 

Re: sundial taxonomy

[John Davis]

Hi All,

I'll buy this, and put in in the next draft of the Glossary.  I really don't
want a different term for every possible type of dial!

Regards,

John

Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]


- Original Message -
From: Patrick Powers [EMAIL PROTECTED]
To: sundial sundial@rrz.uni-koeln.de
Sent: 27 February 2000 20:28
Subject: Re: sundial taxonomy


Message text written by Sara Schechner

As an alternative approach we could get round this by specifying
the angles of universality.  e.g., UNIVERSAL 60°N - 10°S

I would go with this.  I don't like the idea of something being 'partly
universal'.  It seems to me things are either universal or they are not.
[A similar problem also can occur with use of  the word 'unique'].  If one
states the boundaries within which the device is universal that is far
better to my way of thinking.  But then maybe I am a pedant.

Patrick

Sundial Glossary Update

[John Davis]

Happy New Year to all 
diallists!

To prove that I haven't got too much of a hangover, a new 
version (including downloadable files) of the Glossary is now online at 

www.btinternet.com/~john.davis

This version has a major upgrade of 
the text, based on all the inputs I have gratefully received from you all. 
Hopefully, I have acknowledged everyone who provided comments - my apologies if 
I've missed you; let me know and I will correct.

Other than adding new terms and correcting existing 
definitions, the potentially contentious changes made include:
 giving equatorial dials priority over 
equinotial ones
 measuring 
inclination of a dial to the back of the dial face.
 justifying the use 
of positive longitudes to the west and measuring azimuth from the 
south.

At this stage, I haven't made any much-needed changes to 
the symbol set, as I'm waiting for input from some key BSS members who are not 
e-mail enabled. Also, diagrams have still to be added - this will be a 
major job and the corrections took me longer than I expected!

Bob Terwilliger has kindly stepped in to help on the html 
front. I have not had time to incorporate his ideas in this version, but 
you can expect a more presentable web format in the future - I'm still 
concentrating on a printable version.

Many thanks for everyone's help so far,

John

Dr J R DavisFlowton, 
UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

Chinese dial

[John Davis]

Hi Dialling Colleagues,


A member of the public (i.e. not a sundial enthusiast)  contacted me for
help with an item which was sold to him by an antique dealer as a mid-18th
century Chinese sundial.  He wanted to know something about it, and
particularly how to set it up and read the time.

I've put two pictures of the dial at:
www.btinternet.com/~john.davis/chinese.htm

I have never seen a dial like this before.  I would describe it as an
ecliptic plane dial, and believe it works as follows:

  In use, the dial is first placed facing south.  Then,
on a given day, the elevation of the segment of a circle which comprises the
main part of the dial would be set, by the geared mechanism, to put it into
the ecliptic plane.  Then, the movable radius is adjusted so that it is
pointing towards the sun and the shadow of its outer end falls on the centre
of the circle.  The time is read off a scale on the circumference of the
circle, at the rate of 15 degrees per hour.  As the segment seems to have an
included angle of about 60 degrees, the dial could be used for two hours
either side of noon.

Has anyone seen a similar dial?  Also, can anyone confirm (or dispute) from
its general style whether it is really likely to be mid-18th century
Chinese?  What system of hours was likely to be in use at that time?

Happy pondering,

John.

Introductory astronomy sites

[John Davis]

Hi all,

Please can anyone point me at suitable URL's of basic astronomy, capable of
answering questions of the why does the sun rise in the East and what
causes the seasons? type.  I have a contact at the local museum who is
putting together an astonomy/sundial trail for primary schoolchildren and he
needs background material.  He will also be teaching the children to make
cardboard dials, so we might get some more recruits at some time in the
future!

Thanks in anticipation,

John

--
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

Sundial Glossary - out now

[John Davis]

Hi Dialling Colleagues,

I'm pleased to announce that the first edition of the BSS 
Sundial Glossary is now available.

The Glossary is A4-size, has soft covers andhas 42 
pages (similar to a BSS Bulletin). Printed versions can be obtained 
from:

Ms Margery Lovatt, BSS Sales
Studio 5, Parndon Mill
Harlow
Essex
CM20 2HP
UK

The cost is £6.50 (UK), £7.00 (EC) and £8.00 (Rest of the 
World), all prices including post and packing.Cheques (to BSS) and money 
orders in pounds sterling, please.
 
Thanks to some tremendous work by Bob Terwilliger on the 
look-and-feel, and Ian Wootton's good offices, the Glossary is also viewable 
on-line (free!) with a link direct from the BSS front page at:

 www.sundialsoc.org.uk


In addition to mentioning Bob and Ian, I'd like to thank 
everyone in the sundialling community who helped in this project. I can't 
mention everyone by name, but it was Margaret Stanier who got it through the 
publishers.

The second edition is now underway, so if you have any 
comments or suggestions for additions or corrections, please contact 
me.

Have fun,

John
--
Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

Re: Nought at noon

[John Davis]

Steve,

I believe I have seen this use of 0 for noon very occasionally on English
vertical dials - although at the moment I can't think where!  I believe Bob
Terwilliger is right - it's done for spacing reasons, and possibly the maker
isn't religious!

John
---
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: Steve Lelievre [EMAIL PROTECTED]
To: Sundial mailing list sundial@rrz.uni-koeln.de
Sent: 18 July 2000 15:29
Subject: Nought at noon


 I have recently seen a couple of dials which use a nought (a digit zero)
in
 place of XII, whereas the rest of the hour labels are in their usual roman
 numeral forms. In other words, they run VI, VII...XI, 0, I, II...VI. One
 dial is from the 1950s and the other from the 1960s. They are both located
 in Nova Scotia and presumably made in Canada or USA. I don't know the
makers
 of either, but I'm sure they are not made by the same company since the
 quality and designs are so different.

 I've never seen this done on a clock, it's not a bona fide roman number,
and
 I can't think of any reason not to mark it as the 12th hour. Why does 0
 appear, and is it common practice to use it?

 I read in the BSS Glossary that a cross (looking like an Iron Cross, or as
 five dots) is sometimes used in older sundials to indicate the noon
 position. Are there any other symbols in use?

 Cheers, Steve


 Steve's Site is at http://www3.ns.sympatico.ca/steve.lelievre

Re: IIII at IV

[John Davis]

Hi all,

I used to think that, in dialling (rather than clocks), the  form was
gradually replaced with the modern IV.  However, I have recently come
across a case where an old vertical dial (a wooden great decliner) was
replaced by covering it with a newer one.  The original dial has been dated
at 1590-ish, and has the IV form.  The newer one, which I would put at the
mid 1700s, uses !  I have no explanation of this, other than the
personal preferences of the makers.  The two dials are very similar in
layout, so the space resrtictions are the same in each case.

Cheers,

John
---
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: [EMAIL PROTECTED]
To: Sundial mailing list sundial@rrz.uni-koeln.de
Sent: 21 July 2000 08:50
Subject:  at IV


 I've been following the discourse on 'Nought at noon' and
 this has reminded me of an anomoly which has puzzled me for
 years.

 In my school technology course we undertake a project on
 time and so we get a lot of clocks and sundials which the
 students design and make.

 A  question I am often asked is why do English clocks with
 Roman numerals have  (instead of IV) at the '4'
 position and most Continental and American clocks appear to
 have the correct IV?

 Was this an error on the part of some early clockmaker
 which was continued eventually to become a tradition or is
 there some other reason?

 Get your own zoom email - click here - http://www.zoom.co.uk/

Design challenge

[John Davis]

Hi all,

I have a question/challenge to all you sundial designers:   what is the most
accurate design for a Standard Time dial?

The reason behind the question is to find a way to stop members of the
public looking at a public dial, inspecting their watches, and concluding
that dials never tell the right time!

The criteria for the dial are, in my opinion:

a) it should tell Standard Time, (or possibly Daylight Saving Time - BST in
the UK)
b) it should be in a fixed location
c) it must have no moving parts (which rules out adjustable equatorials and
changeable gnomons etc) and
should be as physically robust as possible.
d)  it must not require reference to a separate table or computer program eg
to get an exact declination for the sun.
All data must be built into the dial plate.
e)  the accuracy should be interpreted as the mean error for the hour
lines 3 hours either side of noon (or 12:00)  for the years 2000 to 2050.

As a starter, the Singleton dial recently discussed here would seem to be
a reasonable candidate.  It's main limitation, common to all dials which
incorporate an EoT correction, is that it is drawn for a some MEAN EoT
curve, and no allowance is made for the leap year cycle and the other minor
variations.  Is there some geometry of dial plate and style which minimises
the time error caused by small year-to-year variations in the mean daily
declination? If this is achieved, then the small change in the EoT over a
single day may be allowed for.

There is no prize for the competition, but I promise I will build a physical
example of the best suggestion, and share it with the list!

Happy designing,

John

--


Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

Thanks - CAD Help

[John Davis]

Colleagues

Thanks to all of you who responded with help in 
translating CAD files into a format suitable for drawing packages. I was 
guided to Paintshop Pro v5, which I already had, but then found that my 
venerable CAD program (TurboCAD v3) produces a rather non-standard .dxf format 
which messed up some of the lines, and lost the special fonts. 


The "Print screen" route also worked, but the resolution 
was low.

My current stop-gap solution (until I get a more 
up-to-date CAD package) has been to print out at 1440 dpi and scan back in 
again, saving as a .gif! Messy, but it's surprisingly 
effective.

BTW - the task in question was some diagrams for the 
Sundial Glossary (Draft 7), so the question wasn't entirely 
off-topic

Cheers,

John
---
Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

Re: Ceiling Dials

[John Davis]

There is a well-known ceiling dial at the Horniman Museum.  It was designed
by BSS-member John Moir (amongst others).  I'm sure he would be please to
discuss details with you.

John

Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: Gordon Watson [EMAIL PROTECTED]
To: sundial@rrz.uni-koeln.de
Sent: 02 May 2000 17:10
Subject: Ceiling Dials


 Greetings from Devon, England.

 Anyone made a ceiling dial--a mirror by a window
 projecting the sun's image onto the ceiling marked
 with hour lines? I have been considering making
 one for years and am hoping to find information
 on the net, but so far without success. Do you
 know of any ceiling dial articles on the net?

 Issues that have come to my mind include:

  1. Mirror mounting/size/shape.
  2. Whether to raise or tilt the mirror in order to
 to reflect the sun onto the ceiling on more days
 of the year or at more convinient times of the day.
  3. Perhaps include an analemma (or two) with dates marked.

 I have found the reference to an article in the March 1996
 issue of the NASS Journal entitled A Kitchen Ceiling Analemma
 by Woody Sullivan. Also, in the April 2000 issue of Sky  Telescope
 in the 25 Years Ago section, the April 1975 front cover is reproduced
 sporting a tantalising photograph of analemmas painted on a ceiling.

 Gordon Watson
 Lat. 50:30 N, Long. 3:45 W

Re: Fibre optic cables

[John Davis]

Hi Mike,

For hobby supplies in the UK, try Maplins at www.maplins.co.uk.  They
deliver next-day.  Other likely suppliers are Farnell and RS Components. - I
think I can find contacts if you don't know them.

John
--
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: The Shaws [EMAIL PROTECTED]
To: Mailinglist Sundial sundial@rrz.uni-koeln.de
Sent: 03 May 2000 07:42
Subject: Fibre optic cables


 Dear knowledgeable sundial folk,

 At the recent BSS conference, one of the sundial competition prizewinning
 entries was a remote reading sundial based on fibre optic cables.  There
is
 also an article about a similar one in BSS Bulletin 89/2 Page 16 by
 W.G.Benoy.

 I rather fancy having a go at making such a dial - but know nothing
 whatsoever about fibre optic cables.

 Where do you get them from?
 Do you buy a long piece and cut it to length?
 I assume they come in different diameters?
 Any help appreciated

 Mike Shaw

 [EMAIL PROTECTED]
 53.37N  3.02W
 Wirral, UK

Re: Sundial by Sir Christopher Wren

[John Davis]

Hi Mac et al,

If you're looking for photos of the Wren dial, I have some that I took last
summer.  I can scan them for anyone that wishes, but the files would need to
be quite large to convey all the detail.

Regards,

John
-
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

.

 If any on the Sundial List are interested in Wren's magnificent
 sundial at All Souls College but haven't seen it, I have a small jpg
 (about 45k) available.  There must be better images available
 somewhere on the internet, but I don't know where at the moment.

 Best wishes,

 Mac Oglesby

Re: analemmic vs. analemmatic

[John Davis]

Hi John.

In the BSS Glossary, I have defined an analemmic dial either as the one you
describe, with analemmas on the hour lines, or as the type of dial which
uses a gnomon with an analemma (or half-analemma) shape incorporated.  This
seems to fit with modern usage, and is a working definition unless anyone
can authoritatively point me at a better one.

I think the definition of an analemmatic dial is non-controversial.

Regards,

John

---
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: John Carmichael [EMAIL PROTECTED]
To: sundial@rrz.uni-koeln.de
Sent: 09 May 2000 15:26
Subject: analemmic vs. analemmatic


 Hello all:

 I need to know the proper classification of the Swenson dial or a similar
 dial by Father Ildephonse at the convent of Cimiez-sur-Nice (picture on
 plate 19 of Rohr).  These dials have the analemma for each hour only.

 Would these be called hourly analemmic sundials (not to be confused with
 analemmatic sundials)?

 I've noticed that some people simply call this type of dial Standard Time
 sundials, but this seems to be too general.

 Thanks,

 John Carmichael
 Tucson Arizona

Re: beaded analemma date sequence

[John Davis]

Hi all,

Doug Bateman's excellent noon window dial at the Defence Evaluation and
Research Agency, Farnborough, is essentially a beaded analemma with one
spot per day.  It uses slightly larger spots for days 5,10,15,20,25 and the
last day of the month.  Days 10,20 and last (whether 28,30 or 31) are
numbered.  This was a carefully considered choice, maximising the eveness of
the spacing, legibility, and the best way of conveying the information.  The
scheme avoids the awkward short space of 1 to 5, or the inconvenience of the
6,11... sequence.  The only disadvantage is that the observer is left to
deduce that the first day of the month follows 28, 30 or 31 - most visitors
to DERA manage this!

The dial is illustrated in the BSS Bulletin Vol 12(i) pp42-44 February 2000.

Regards,

John
--
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: John Carmichael [EMAIL PROTECTED]
To: sundial@rrz.uni-koeln.de
Sent: 03 October 2000 16:03
Subject: beaded analemma date sequence


 Hello All:

 Ron Anthony and I have been having a discussion concerning the proper date
 sequence of a beaded analemma (an analemma which has dates marked on
it).

 We noticed that the Shadows sundial generator program has analemmas with
the
 following dates of each month: 1,6,11,16,21,26.  Why would this sequence
be
 better than: 1,5,10,15,20,25?  Certainly the average sundial user would
find
 it easier to read 1,5,10 etc.

 John Carmichael
 Tucson Arizona

Re: Bifilar Again!

[John Davis]

Hi Claude,

You wrote:

The new BSS glossary does not even list the term,
 bifilar.

This is not so - it is there under dial types, and reads:

bifilar ~: invented in 1922 by Hugo Michnik in its horizontal form, although
it can be on any plane.  The time is indicated by the intersection on the
dial plate, of the shadows of two wires (or other lines in space) stretched
above and parallel to it.  The wires often run E-W and N-S, with their
(different) heights above the plane being a function of the location of the
dial. It may have equiangular hour markings, and hence can be delineated to
show many kinds of hours.

Whilst we might discuss whether the definition needs extending to cover
non-straight wires, I think this covers the most usual forms,

Regards,

John



Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

Re: beaded EOT graph available

[John Davis]

Hi John,

I'd like a copy of the file, please.

An alternative to an EoT graph (which some members of the public find
surprisingly difficult to read), many old dials used a form of table, often
curved around the dial.  The months, with individual days, were laid out in
a linear (or circular) strip, with a nonlinear scale of EoT (in whole
minutes) running next to it.  I've recently put this on a new dial, and find
that it can be read to half a minute on any day.  This is about the same
accuracy that the 12 horizontal dial can be read to.

Best regards, and thanks for making the DeltaCAD file available,

John
---
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: John Carmichael [EMAIL PROTECTED]
To: sundial@rrz.uni-koeln.de
Sent: 08 November 2000 15:27
Subject: beaded EOT graph available


 Hello All:

 About a year ago, Tony Moss made some beautiful 4 x 8 inch bronze Equation
 of Time plaques for me.  When we were working on their design, I
originally
 wanted them to have horizontal lines of one minute increments and vertical
 lines of five day increments. This made a graph which was very busy with
way
 too many closely spaced lines, so we ended up using horizontal lines of
five
 minute increments and vertical lines with 5 day increments.

 To avoid using so many lines, I recently designed a beaded EOT graph with
 beads on the curve representing dates at ten day increments, and
horizontal
 lines with one minute increments. I also indicate the solstices and
 equinoxes with larger beads. This version is attractive, precise and very
 easy to read.

 If anybody would like my original Delta Cad file (14.2 KB) of my beaded
EOT
 graph please tell me and I'll send it as an attachment. (note: you must
have
 Delta Cad to view this.  Unfortunately,I tried converting the DC file to
 GIF, JPEG, and BMP files, but for some reason the beads don't show up in
 these formats).

 Best

 John Carmichael
 Tucson Arizona

 p.s To draw this graph on Delta Cad, I went about it in a roundabout way.
 Because there are no programs available for drawing customized Delta Cad
EOT
 curves, I scanned the EOT graph in the Shadows generator program and
placed
 the scanned photo in DC. Then I traced over all the lines, added some nice
 text and borders, then erased the photo.

 pps. It would be nice to have a DC macro which would allow the user to
draw
 customized EOT graphs with different time and date increments and
different
 allowable spacings between these lines. This way, you could make EOT
curves
 of different sizes and shapes which would be convenient for adding to dial
 faces that have limited available free space.

Fonts for sundials

[John Davis]

Hi all,

Does anyone know of a good source for computer fonts 
(preferably Windows-compatible) of antique characters? Old hand-engraved 
dials had a very particular style which it is difficult to replicate with modern 
fonts. For example, the figure "8" was often flat-topped, as was 
the"3", and it and  the "5"s and "7"s usually extended below the 
line.

The Roman numerals for the hour-ring were usually very 
tall and thin, with extreme variations between the thick and thin strokes, and 
very narrow gapsbetween letters (eg in III). It is time-consuming 
generating these from scratch, or stretching existing characters. 


The reason for the question is that I'm making a replica 
or the 17th century dial (from poor-quality photos!) and it is difficult to get 
the "feel" right.

Any help would be gratefully received.

John
-
Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

Re: FONTS

[John Davis]

Hi Mike et al

I got two responses from my original request:

Andrew James suggested http://www.gate.net/~shipbrk/typograf.html  The JSL
Ancient font which is available as freeware from this site has the long s
and several other characteristic pairs of letters including ct, st and
sh.  It has a slightly
hand-drawn feel.

Dave Bell suggested http://www.fontcraft.com/scriptorium which is a
commercial font house.  They have hundreds of fonts, and I am currently
contacting them to find which are the most suitable.

I hope this helps - please let us all know if anything else appears as there
seem to be several Mailing List readers interested.

Happy scripting,

John
---


Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: Mike Cowham [EMAIL PROTECTED]
To: sundial@rrz.uni-koeln.de
Sent: 12 November 2000 16:59
Subject: FONTS


 Dear Shadow Watchers,
 As we have been discussing fonts recently, let me tell you of my
 particular 'wants'.
 I want an old Roman type font with the old fashioned s that is
 shaped like f, but without the cross bar.  Ideally the font should also
 include the double letters like ct that were often run together as one
 character.
 I have found some gothic type fonts like this, but alas, not a
 Roman one, such as was used in many books of 17/18 centuries.
 I do have a disk with 1000 fonts, and another with almost as
 many, but looking through the listings has not helped.  Most of these
 fonts are way-out modern ones.  I suppose that the nearest font found is
 PLANTIN, as used? by Plantin Moretus of Antwerp.

 Regards,
 Mike.
 [EMAIL PROTECTED]
 Cambridge, UK.

Re: Needed: history of equation of time

[John Davis]

Hi Gordon,

According to my research for the Sundial Glossary, Huygens was the first to
publish an accurate EoT table in 1665, and he republished this in his
Horologium Oscillatorium in 1673.

Flamsteed calculated the first accurate English table in 1665, when he was
only 19, but it was not published until 1669, in De Aequatione Dierum.

Unfortunately, I cannot remember easily where I came by this information.
If you get a clearer picture, I would be grateful if you would share it with
the List.

Best regards,

John
--
Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

- Original Message -
From: Gordon Uber [EMAIL PROTECTED]
To: sundial sundial@rrz.uni-koeln.de
Sent: 27 November 2000 07:35
Subject: Needed: history of equation of time


 I have become interested in the history of the Equation of Time. Can
anyone
 recommend a reference (preferably in English) on the subject?

 I understand that John Flamsteed and Christiaan Huygens published tables
of
 it in 1666 and 1662, respectively. If anyone has copies of these tables,
 the tables (or citations to them) would be greatly appreciated.

 So far I have located G. Toomer's translation of Ptolemy's Almagest,
 which has a section on it, as does Neugebauer's History of Ancient
 Mathematical Astronomy.

 I am following up on some articles in the NAWCC Bulletin.

 Any help would be greatly appreciated.

 Gordon

 Gordon Uber   [EMAIL PROTECTED]  San Diego, California  USA
 Webmaster: Clocks and Time: http://www.ubr.com/clocks

Re: sunspots

[John Davis]

Hi John,

 Does anybody know the difference in the apparent diameter of the sun, in
 degrees, between perihelion and aphelion?  Is this significant?

The info you want is in the BSS Glossary (plug, plug!) under semidiameter.
The answers are 15.76 arcmins in July (aphelion) and 16.29 arcmins in
January (perihelion).  For the purposes of looking at sunspots, I'd say this
was insignificant.  If the differences were much larger, it would have a
noticeble affect on the seasonal temperatures!

Best regards,

John

Dr J R Davis
Flowton, UK
52.08N, 1.043E
email: [EMAIL PROTECTED]

Re: mystery curve

[John Davis]

Hi all,

While researching the BSS Glossary, I looked up the term 
"Lemniscate" in a mathematics dictionary. This is the term used, I 
believe, for the analemma in the Latin countries, and originally meant 
"ribbon-like". According to the dictionary, in English the lemniscate 
curve is similar to a spiral but differs from it principally because "... there 
is a slight falling off of the rate of increase of radial acceleration as the 
distance from the starting point increases" (!) As a result of this, it 
isused in road design as a transition from a straight road into a circular 
arc.

The diagram in the dictionary comparing the lemniscate, 
spiral and cubic parabola shows the first of these to look like one lobe 
ofan analemma.

So, there was a closer connection between Mike's original 
question and dialling than we might have originally thought!

Best regards,

John
-
Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

  - Original Message - 
  From: 
  Peter 
  Abrahams 
  To: sundial@rrz.uni-koeln.de 
  Sent: 11 February 2001 23:15
  Subject: mystery curve
  There is a curve for which the transition from one radius 
  of curvature to another is as gradual as possible. I too have 
  forgotten its name however it can be formed by bending a length of 
  material of constant stiffness (such as a garden hose) into a loop by 
  holding only its ends.That's a catenary.I don't think the 
  occupants of a car would guide it through a path that would cause them 
  discomfort. So even if a road did have a jump in radius of 
  curvature, the path traced out by a car wouldn't. (Unlike a 
  roller coaster, a car doesn't have to travel out any particular 
  path).No, but you do want to encourage drivers to stay in their 
  lanes.--Peter___Peter 
  Abrahams [EMAIL PROTECTED] The 
  history of the telescope   the binocular: http://www.europa.com/~telscope/binotele.htm

Dial on TV

[John Davis]

Hi folks,

Did anyone else spot the sundial in the (British) TV 
advert for the 2001 Census?

It is the vertical decliner at Aldeburgh, Suffolk, BSS 
Serial No 0665. It is on the end of the Old Moot Hall, under some 
tremendous chimneys. The building is now (thanks to coastal erosion), 
right on the foreshore. The dial dates from 1650 and is a very smart black 
and white, with a gilded swan-neck pediment.

You have to be quick (or set your video recorders!) as it 
is only on-screen for a couple of seconds!

Happy dialling,

John

Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

Re: Solar Noon Equation of Time Calculator

[John Davis]

Hi Gianni et al,

Re. the Longitude convention: note that conventions 
are just that and, by definition, aren't right or wrong but accepted (or 
not). When I wrote the BSS Glossary, I consciously avoided using the IAU 
definition (0-360 degrees, Eastwards positive) in favour of the one almost 
universally used by diallists and navigators for four centuries (-180 to +180 
degrees, Westward positive). The astronomers can use what they like, but 
they don't rule the world and the rest of us (like Steve Lelievre) use what is 
convenient.

For the Second Edition of the Glossary (in preparation), I 
have stuck to my original definition but have added a note that the IAU one is 
different.

The other area where I (and Jean Meeus) are at odds with 
the IAU is the sign of the EoT, but that's another can of 
worms.

The key thing is to be consistent in a document and to 
make sure that the reader is given enough information to get the right 
answer.

It's clear that we could do with a term for (EoT + 
longitude correction). I didn't find a common one in my trawl through the 
literature, though the NASS Dialist's Companion uses "Total Correction" which 
seems reasonable. However, there are still chinks not defined, such as: is 
the atmospheric refraction correction included?

I quite agree that a table of the mean EoT over a long 
period (the lifetime of a sundial) is very useful as an addition to the exact 
EoT for a particular date/time. The new Glossary will include the one 
which you (Gianni) so kindly gave me.

Best regards to all,

John
--
Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

  - Original Message - 
  From: 
  Gianni 
  Ferrari 
  To: sundial@rrz.uni-koeln.de 
  Sent: 01 May 2001 16:13
  Subject: Solar Noon  Equation of 
  Time Calculator 
  Hi Piers ,I have visited with a lot of interest your Solar 
  Noon Calculator on the webat www.solar-noon.com and I have immediately 
  made some tests to compare yourvalues with those calculated from me and 
  published in an article in theproceedings of our "X Seminario 
  di Gnomonica" ( X Italian Meeting onSundials - 2000)Here are 
  some considerations of mine1)From the comparison I have 
  immediately seen that your results are wrongbecause of a banal error: 
  anywhere the value of the EoT has been or takenwith opposite sign or 
  subtracted instead that added.An example : Long. =12d E and TZ of 
  Central Europe (central Meridian 15 dEast): longitude correction =+3d = 
  +12mAt 1/1/2001 the exact value of the Eot = - 3m41s an so :- 
  Local Apparent Time (apparent solar time) = 12h- Local mean time (local 
  mean solar time) = 12h 3m 41s- Standard Time = 12 15m 41s (NASS Dialist 
  Companion gives the value, lessapproximate, 12h 15m39s )In 
  the Table calculated with the Solar Noon Calculator is written the value= 
  12h08m48s, value that is obtained adding (instead that subtracting ) 
  thevalue of the Eot: 12h+12m+(-3m12s) = 12h08m48s2)The table 
  of the EoT NOT gives the values of the EoT but the Totalcorrection that it 
  is necessary to add to the Local Apparent Time to obtainthe Standard Time 
  : it is therefore the sum of the EoT + longitudecorrection..This value 
  is certainly very useful but, perhaps, it is necessary to givesome 
  explanations and it is opportune not to call it EotMoreover in this 
  way the table with the values of noon is useless becausethese values are 
  equal to those of the EoT + 12hThe definition :"Equation of Time 
  displays the difference between solar time and thestandard times where you 
  are"(note at the foot of the page) it is not correct.Davis' Sundials 
  Glossary gives the following:Equation of Time: the time difference between 
  Local Apparent Time (apparentsolar time) and mean solar time at the same 
  location (NOT Standard Time).Its value varies between extremes of about 
  +14 minutes in February and -16minutes in October.3)Checking 
  only for the date 1/1/2001 I have found that the error between theexact 
  value and the mean value of the EoT = 3m41s -3m12s=29 sec: almost 
  thedouble of the maximum error (in the Note).With NASS Dialist 
  Companion we obtain the less approximate value Eot =3m37s: also with 
  this value the error would be of 25sDoes the greater error depend on the 
  fact that the Eot has been calculatedat 0h (UT) instead that at 12h 
  (UT)In fact the Eot can also change till 20s a day.4)In my 
  opinion it is very useful, for instance in the construction ofsundials 
  with mean time, to have a table of the mean values of the Eot (asof the 
  mean declination of the Sun), while the table that gives the 
  meanlocalnoon (mean on 4 years) can be used in a wrong 
  way.In fact these tables, that should be used only for the search of the 
  meantime from the apparent solar time given by a sundial, could be 
  consideredright also in the search of the declination of the walls.In 
 

Fw: Historical locations and longitudes

[John Davis]

Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]
- Original Message - 
From: John 
Davis 
To: Mailinglist Sundial 
Sent: 19 July 2001 15:09
Subject: Historical locations and longitudes

Hi colleagues,

I have recently had the opportunity to inspect a superb 
bronze horizontal dial made by George Adams (the elder) in the second quarter of 
the 18th century. 

Amongst other exiting details of the engraving, it carries 
the names of 32 cities or locations worldwide in the chapter ring. The 
names are evenly distributedwith two between each pair of hour numerals, 
but small arrows identify the time of noon at these locations (compared to that 
of the dial, located at around 1 degree East) to the nearest 
minute.

Many of the cities still have the same names: Dublin, 
Lisbon, Boston etc. Some are easy to guess: Dantzick = Gdansk; 
Constanstinople = Istanbul; Berbadoes = Barbados etc. However, some have 
me baffled and hence I'm posting this looking for help, please. Can anyone 
identify the following locations, with very approximate longitudes calculated 
from the dial. I say approximate because some of the known cities have 
large inaccuracies compared to modern values, eg although Lisbon is right to 
half a degree, "Pekin in China" is 16 degrees off the value my atlas gives for 
Bejing!

Name on 
dialLongitude

Fort St George  
  86d E (perhaps Madras?)
Cape Comorm  
  79d E
Isphan  

 56d E
Cainiec27d 
E
St Mich. Isle  
   28d W
Ca. Spir 
Sancto41d 
W
Ca Fare 
Freezld50d 
W
Port Concepn  
  110d E
Compostetta117d 
W

Note that the engraving makes some characters difficult to 
read and the above list might have mis-identified in for m,f for the long 
s etc.

Here's hoping the list includes some historical 
cartographers!

John
-
Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

Fw: Longitudes - Thanks

[John Davis]

Hi colleagues,

Thanks to all who responded to my request for historical 
locations and longitudes for the C18 Adams dial. As ever, the List is fast 
and comprehensive. Special thanks to Bill Thayer, Andrew James, Brad 
Lufkin, Fred Sawyer, G Faltlhans, Frank Evans and Peter Mayer - apologies if 
I've missed any responses.

I've just about filled in all the gaps on my list now and 
am busy comparing the results, both with real life and with other period dials 
that use the same list. I suspect that the dial makers had a published 
list that they referred to for years, without checking the latest navigational 
information. Some of the longitudes are over 10 degrees off, on a dial 
which generally shows high precision and accuracy, and I can't believe that 
sailors could have found their way with that degree of uncertainty!

Regards,

John

Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

Re: Sundial Slang

[John Davis]

Hi John et al,

I couldn't let this pass without comment :-) 
!!

I'm not sure that I am in any position to "approve" the 
correct terms - the BSS Sundial Glossary is just a collection of the bits of 
information that I've pulled together from various sources, including much input 
from the participants of this list. I have no problem with the use of 
slang terms, especially when they help those poor unfortunates that aren't 
sundial enthusiasts know what we're talking about. It does need care, 
though, not to introduce or reinforce misapprehensions. Most of John's 
terms seem to avoid this, though whether they are more easily understood than 
the "scientific" term is debatable.

One term which is common and not (yet) in the Glossary is 
"High noon". Is this an americanism? I have, of course, seen my 
cowboy movies, but am unclear where the term originates. Is it that, with 
the relatively low latitudes in the south of America, the Sun can come close to 
directly overhead (altitude = 90 degrees) at noon? If so, it reinforces 
the wrong view of much of the UK media that the Sun is at the "zenith" at 
noon. Whilst many ordinary people think of "zenith" as the highest point 
of the arc, astronomically it is defined as the point which really is directly 
overhead (only expressed rather more formally!).


Another point to watch is the use of 
"due north" instead of celestial pole. If you are at northerly latitudes, 
the difference betweencelestial and geographic north can be 
significant. Why not use the Pole Star as a better everyday 
approximation?

"Horizon pollution" is an 
interesting term. I guess we would define this as a percentage of the 
daylight period when the Sun falls on a particular site. It's difficult to 
come up with a mathematical definition, as it depends on the Sun's declination 
as well as the positions of any obstructions. Do we know of any dials at 
locations which can show the time over the full sunrise-sunset period thoughout 
the year?

Regards,

John
--
Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

  - Original Message - 
  From: 
  John Carmichael 
  To: sundial@rrz.uni-koeln.de 
  Sent: 17 August 2001 16:07
  Subject: Sundial Slang
  
  
  Hi All,
  I've just finished the 
  7th edition of my Sundial Owner's Manual and realized that 
  throughout the manual I explained sundial terms using sundial slang instead of 
  the John Davis approved correct term. (Although at least in the Manual I place 
  the correct term next to it in parenthisis) I also use sundial slang when Im 
  talking with others. I feel a 
  little guilty because Im not using the correct terms. But the slang serves a very useful 
  purpose in that it is so intuitive and self-explanatory. (The sundial purists are going to hate 
  me for this!)
  
  Anyway, here are a few of 
  them
  *High noon (Apparent 
  Noon)
  Fuzz zone 
  (The penumbra)
  Fuzz 
  factor (formula that determines the width of the penumbra: F=1/100) The 
  Correction graph (The Equation of Time)
  Sun 
  height (solar altitude)
  Sun 
  direction (solar azimuth)
  Due North 
  (The Celestial Pole)
  Sun time 
  (Apparent Time)
  Watch 
  time (Standard Time)
  Date Ball 
  (Spherical Nodus)
  Shadow 
  caster (gnomon)
  The edge 
  of the shadow caster (style)
  Moontime 
  (time shown by moon shadows on a sundial)
  Time Zone 
  correction (Longitudinal Shift) 
  Horizon 
  pollution (the objects around sundial that shade it from the sun. ie. trees, buildings, mountains. No correct term for this that I know 
  of)
  *As a sundial slang purist, I get 
  upset, like any good dialist would, when my favorite radio station announces 
  that it is High Noon (12:00 pm watch time), but because of our Time Zone 
  Correction, its really only about 11:30 am Sun time! 
  John
  
  John L. Carmichael Jr.Sundial 
  Sculptures925 E. Foothills Dr.Tucson Arizona 85718USA
  
  Tel: 520-696-1709Email: [EMAIL PROTECTED]Website: 
  http://www.sundialsculptures.com

Re: Sundial Slang

[John Davis]

Hi Mario,

Thanks for your most informative input.

As I understand from your medieval French, the "high" 
prefix as in "high noon", "high tierce" etc, means a time justbefore the 
period of noon, tierce etc (?). Then "bas tierce" etc would be the time 
just after. Do you have a conversion of the French terms into 
(approximate) modern times? These "extra" cannonical hours are then 
similar to the half-tides in the English Anglo-Saxon timekeeping.

These extra terms do shed some light as to why "Nones" - 
the Latin ninth hour after sunrise - got to mean the modern midday or 12th 
hour. It seems likely that high noon just got shortened when there was no 
need for the distinction between high noon and noon.

Regards,

John

Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

  - Original Message - 
  From: 
  Mario Arnaldi 
  
  To: Sundial 
  List 
  Sent: 18 August 2001 11:08
  Subject: Re: Sundial Slang
  
  
  
- Original Message - 
From: 
Mario 
Arnaldi 
To: John 
Davis 
Sent: Saturday, August 18, 2001 12:11 
AM
Subject: Re: Sundial Slang

One term which is common and not (yet) in the Glossary 
is "High noon". Is this an americanism? I have, of course, seen 
my cowboy movies, but am unclear where the term originates. Is it 
that, with the relatively low latitudes in the south of America, the Sun can 
come close to directly overhead (altitude = 90 degrees) at noon? If 
so, it reinforces the wrong view of much of the UK media that the Sun is at 
the "zenith" at noon. Whilst many ordinary people think of "zenith" as 
the highest point of the arc, astronomically it is defined as the point 
which really is directly overhead (only expressed rather more 
formally!).

  ---
  
  Hi all,
  this my response may be a little more serious 
  (hope don't bore you), though I really don't know where the slang said 
  'Hight Noon' comes from.
  Nevertheless I should remark that in middle 
  age England and French people use to call midday just like this, "hygh 
  noone", or "haute nonne". As we know the English language got much from 
  the French language in the middle age, and we know also that modern word 
  "noon" comes from "none" (or Latin 'nona') that is the cononical hour when 
  monks recite none, that in the ancient Irish language surelybecome 
  "Noon". There is, actually in the Vatican library an ancient 
  Irishmanuscript that use this term to say "none" (see my book "The 
  ancient sundial of Ireland", page 66), and because since early times the 
  pryer of none has been slowly superimposed to midday, we find that in 
  England people easily called that moment 'noon'.
  But lets go bak to high noon again. As I 
  wrote here, medieval French use to call midday "haute nonne" that means 
  high none (in the sense of the time for pryer), why this? Easy, in 
  medieval time people didn't use the hours as moments like today, but they 
  consider a time between two terms (or hour lines), and canonical hours in 
  former times last almost three seasonal (or temporal) hours, and the 
  position of the sun gave them the idea to specify better. So this is the 
  names of the part of the day in medieval France: heure de soleil levant 
  (hour of the rising sun), prime, houte prime (high prime), tierce, haute 
  tierce (high terce), haute nonne (high none), basse nonne (low none), 
  remontière (wake up), haut vespre (high vesper), bas vespre (low vesper), 
  complie (compline), heure de soleil esconsant (hour of the hiding 
  sun).
  At the same time in England we find the 
  popular use to call midday "hygh noone" as we may read in many old 
  writings. Look at this Cronicle, for instance:"With us the nobility, 
  gentry and students doe ordinarily go to dinner at aleaven before noone 
  and to supper at five, or betweene five and sixe afternoone. The 
  marchaunts dine and suppe seldome before 12 at noone and sixe at night 
  (read evening), aspecially in London. The husbandmen dine also at 'high 
  noone' as they call it and sup at seven or eyght; but out of the terme in 
  our Universities the schoolers dine at tenne".
  
  Thank you for your attention, and forgive me 
  my bad English
  
  Mario
  Mario 
  ArnaldiV.le Leonardo, 82I-48020 LIDO ADRIANO - 
  RavennaItaly
  
  E-Mai:l [EMAIL PROTECTED]Web Site: http://digilander.iol.it/McArdalShop: 
  http://web.tiscalinet.it/McArdal---

Re: Thomas Grice

[John Davis]

Hi Gordon,

According to Gloria Clifton's Directory of British 
Scientific Instrument Makers, Thomas Grice was a member of the Guild of 
Clockmakers, made free in 1675, and known to be making sundials in London in 
1705 (the date on your dial). He had been apprenticed to Richard Ames in 
1667.

However, I have a nagging recollection that Grice is one 
of the names favoured by people making "replica" dials in the 19/20th centuries, 
so you might like to check for signs of authenticity.

Do you have any more details on the dial - or a 
picture?

Regards,

John
---
Dr J R DavisFlowton, UK52.08N, 1.043Eemail: [EMAIL PROTECTED]

  - Original Message - 
  From: 
  [EMAIL PROTECTED] 
  To: sundial@rrz.uni-koeln.de 
  Sent: 19 August 2001 14:27
  Subject: Thomas Grice 
  I have a sun dial by 
  the above inscribed --- Seize the present moment the 
  evening hour is nigh. Dated 1705. Can anyone tell me more about this dial 
  ?? Gordon Pettitt 

Re: Projection Sundials

[john . davis]

Hi David,

The reason that the term projection sundial doesn't appear in the BSS 
Glossary is that it isn't, as far as I'm aware, a term used in the general 
literature.

The dials listed under the term in Sundials Australia are a strange collection 
of dials usually defined under other tems.  There is a ceiling (or reflection) 
dial, an analemmic dial, a noon dial, a sun compass etc etc.  It is difficult 
to see what they have in common.

It would be possible to make a definition for a projection dial based on the 
principle of projecting a spot of light onto a receiving surface, but that is 
just about as general as dials which make shadows on surfaces.  However, there 
are a lot of terms already so I'm not in favour of inventing new ones 
unnecessarily.

But I'm prepared to be overruled!

John Davis (Glossary Editor)

 Dear All,
 
 Could someone help me with a definition of a 'Projection Sundial'.
 
 - Couldn't find it in the BSS Glossary.
 
 - Folkard  Ward 1996 Sundials Australia have included in their section on
 Projection Sundials - The chapel sundial (Merton College, Oxford), a Sun
 Compass, a direct sunlight through a hole onto analemmas on the horizontal
 ground, Monash University Union Building- Melbourne Australia (wall mounted
 rod tipped by a disk making shadows on analemmas on a wall), the Augustus
 Sundial from 9BC, Ulugh Bek's Observatory, mirror sundials shining on
 analemmas on a roof, various noon marks and a Scottish polyhedral 'lectern'
 sundial.
 
 The common factor seems to be that the shadow (or light ray) approximates a
 point rather than a segment.
 
 Is Projection Sundial a recognised term?
 
 What is the characteristic that Projection Sundials have that other sundials
 don't?
 
 
 David Pratten
 www.sunlitdesign.com

Re: Classify sundials?

[john . davis]

Hi Sara,

Thanks for responding - I had remembered our previous discussions on the list 
re classifying dials, but I don't have a quotable reference to what you and 
your colleagues have produced that I, and the other dabblers at dialling, can 
refer to. Perhaps when you return home you could point us to the publication.

Re cylinder dials - whoops, I'm very red-faced at dropping that clanger!  What 
I should have said, of course, is that the gnomon always faces the Sun, not the 
south.

Re moving dial faces, I hadn't intended this to refer to portable dials, but to 
dials in which the dial face and its hour lines have to be specially aligned 
for every reading.  Thus a Butterfield dial, for example, is a portable dial 
but the dial is always set up just like a fixed dial, aligned horizontal  N/S. 
 However, Regiomontanus, Capuchin, quadrants etc have to be pointed at the Sun 
and tilted to align them.  I think this requires an entry in any classification 
scheme.

Re nonius - I agree with you in that the formal name of a diagonal scale is 
transversals - the Second Edition of the Glossay will contain both terms as the 
former is sometimes found in the literature.  The nonius gets a separate entry, 
together with a v. brief biog of Nonez.

Best regards,

John

Re: Making a Dial in The Gambia. What materials to use?

[john . davis]

Hi Mike,

I think Tony's idea of moulding the dial is a good one for DIY construction.  
As another alternative to cement, there are powders which make up to a stone 
substitute, like an outdoor plaster-of-paris.  I have used it for small items 
and it is very good.  Available from arts and crafts suppliers.

For commercial dials that will last several lifetimes, I have been 
investigating vitreous enamel on steel.  This is the technique that was used on 
garage advertisements for petrol etc in the 1920's, as well as railway signs.  
Not something you can do at home, but I got a not unreasonable quote to make 
some 1.5metre diameter dials.

Good luck with the dial - we will expect a report and picture in due course!

Regards,

John
---

 Dear Friends,
 I seem to have talked myself into making a dial in The Gambia, about 13° 
 north of the Equator.  The design is fairly straight forward.  In brief it is 
 to sit on the ground on the south side of the swimming pool at the hotel.  It 
 will recline so as to be visible from the north from a lying position around 
 the pool.  The dial has been calculated for 45°N therefore 45 - 13 means that 
 its plate will be sloping about 32° to the horizontal.  The distance from the 
 pool is about 10m, therefore it needs to be of some size.  I am planning on 
 making it about 2m across.
 The main problem seems to be the choice of materials.  I have ruled out 
 wood due to the termites in the area. I have also ruled out paint as the sun 
 is so very hot most days - except for the 3 months of rains.  It has to be 
 constructed by local labour with minimal materials available.
 I am planning to be there to set it up and work out the delineation but I 
 want to be sure that we have all the materials to hand to build it within a 
 few days.
 At present my thoughts are to make it from concrete, preferably off site, 
 so that it can be laid in position, and dare I say it?, enable me to make 
 small adjustments later if necessary.  This will probably mean that it will 
 have to be made in up to 4 parts plus the gnomon.  The ground on site is 
 basically sand.  I originally considered moulding in the hour lines, numerals 
 etc. but think that this would be too much for the personnel involved.  My 
 latest thought is to make just a flat plate and apply the hour lines as 
 strips - of wood? and house door type numerals.  At least, when the termites 
 eat these strips, they can easily be replaced!
 Therefore I am asking for any other suggestions that may be more 
 appropriate.  I am sure that several members of this list will have made 
 dials for the tropics and eagerly await their comments.
 
 Regards,
 Mike Cowham.
 Cambridge, UK.

Re: Whats the time, where am I, whats on telly?

[john . davis]

Hi all,

A Brown wrote:

 I know John Davis gave a lively talk at a previous BSS meeting regarding 
 the delineating of a dish as a sundial, I believe this may have involved 
 covering the dish with a Mylar membrane.
 I hope I don't have to admit defeat and take out one of those awful 
 microprocessor based finders!
 

I did indeed - the dial (no longer in operation since the advent of digital 
satellites) can be seen on my website at www.flowton-dials.co.uk.  Follow the 
links to Vertical Dials.  If you (A Brown) want a reprint, let me know your 
address.

I believe that there have been some US Patents on solar methods of aligning 
dishes in the past few years which would be worth seeking out.   Good luck with 
an interesting project.

Cheers,

John
---
Dr J R Davis
Flowton Dials

Re: A new sundial - type from Bremen!

[john . davis]

Hi Reinhold,

An excellent dial - thank you for sharing it with us.

Being pedantic, I would describe it as analemmic dial, rather than an 
analemmatic one, but that doesn't detract from its quality.

Regards,

John Davis
-

Re: Slopes and inclinations

[john . davis]

Hi Anselmo et al,

You're right - in English slope and inclination both refer to the angle to 
the horizontal.  This applies both to general usage and the specialist gnomonic 
usage (as defined by the BSS Sundial Glossary at www.sundialsoc.org.uk)

However, whilst the inclination is usually given as an angle, the slope is 
often a ratio, i.e. 1 in 100.

The complimentary angle in gnomonic terms is the reclining angle, measured from 
the vertical.  My preference is not to use this, though, and to stick to the 
inclination.

It's nice to learn something of the origins of our strange language!

Regards,

John Davis
N52d 05m, E1d 08m.


-

Re: Vitruvius or Oughtred?

[john . davis]

Hi Anselmo,

I think the essential difference between these two dials is that, for 
Vitruvius' spider dial, time is indicated by the shadow of the TIP of a 
vertical gnomon; Oughtred's Double Horizontal, on the other hand, uses the 
shadow of the vertical style EDGE.  The curvilinear grids of hour angle vs. 
Sun's declination or altitude look superficially similar, but are to a 
different geometrical projections.

Best regards,

John Davis
51d 05m N:  1d 08m E
-

BSS June Bulletin

[john . davis]

Dear Dialling Colleagues,

On behalf of the editor of the British Sundial Society Bulletin (Dr Margaret 
Stanier), I'm pleased to announce the contents of the June edition of the 
Bulletin will include the following items:

*  A new Sundial on the wall of the National Museums of Scotland
*  Railway Time: the Sundial designed by George Stephenson and his son Robert
*  The Martian Analemma
*  Ancient Sundials of Israel
*  Horizontal Scratch Dials: 2 in Scotland, 1 in England
*  The Pigpen Cipher decoded: from Mrs. Gatty’s Book of Sundials
*  The Sundial in Castletown, Isle of Man
*  A Window-sill Dial at Dartford, Kent
*  Dunscar Wood, Lancashire: human sundial

The edition will be distributed to all BSS members as normal.

Regards,

John Davis
--
Dr J R Davis
Flowton Dials
N52d08m  E1d05m

Re: Shadow Sharpener Again

[john . davis]

Hi Dialling colleagues,

Patrick Powers asked if anyone had practical experience of the bead-in-a-hole 
(pinspeck) shadow sharpener.

I used one experimentally o my Isaac Newton mean-time equatorial dial (see 
www.flowton-dials.co.uk).  It consisted of a 3mm dia phosphor bronze bead 
suspended in a 5.5mm hole in a piece of brass shim.  The dial plate was a 
cylinder radius 240mm.  These values were chosen partly by experiment and 
partly by materials available.

The sharpener worked well at noon, when the shadow appeared about 2mm in 
diameter in a bright annulus.  However, at 9am or 3 pm, when the sun hit the 
nodus at 45 degrees to the axis, the shadow merged into the sides of the 
surround.  This could have been avoided by having a nodus which rotated to face 
the sun but the extra complication wasn't worth the effort.  In the end, I went 
with a simple hole 2mm dia, giving an apparant spot of 5 to 6mm at noon.

The results (including a picture of the resulting shadow) were published in the 
Bulletin of the British Sundial Society, vol 14(i) March 2002.

Anyone else tried one?

John Davis





Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: The heliochronometer

[john . davis]

Hi Bob et al,

heliochronometer is indeed listed in the BSS Glossary, under the Dial types 
category.  The definition given is:

a precision sundial which incorporates some means to allow it to read civil 
(or mean) time.  This is usually achieved by incorporating an EoT cam (as in 
the Pilkington and Gibbs heliochronometer) or by projecting an spot of light 
onto an analemma.  Note: some authors use the term to describe any precision 
sundial

No doubt this definition could be improved on: I shall watch the views of the 
List members with interest.

Regards,

John Davis
---

  from:Robert Terwilliger [EMAIL PROTECTED]
  date:Fri, 21 Jun 2002 12:26:18
  to:  sundial@rrz.uni-koeln.de
  subject: Re: The heliochronometer
 
 Fellow dialists,
 
 What does the group think the criteria for a heliochronometer should
 be?
 
 Is there a definition? John Davis' most excellent glossary does not
 include the term.
 
 Regards,
 
 Bob Terwilliger
 
 -



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Conference dials

[john . davis]

Hi Dialling Colleagues,

For those of you who were not at the British Sundial Society Conference at 
Exeter in April, I have now put pictures of the dials that I displayed there on 
my website.

It has a new URL:  www.flowton-dials.co.uk

Look out for 

* a new page on portable dials, including a compendium,

* some new brass horizontals

* an interesting old slate dial on the Restoration page.

If you spot any glitches with the site, I'd be grateful for a note.

Regards,

John
-


Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: High Noon

[john . davis]

Hi Mac et al,

Following the previous discussion on this topic, I added High Noon to the 
draft second edition of the BSS Glossary.

My understanding is  that it derives from the term haute nones, i.e. the time 
during the period of nones when the sun is at its highest.  Since nones is the 
early pm period, this makes it the same as our noon.  

By contrast, the term bas nones would be the time when the sun is lowest 
during nones, but luckily we have no equivalent modern term Low Noon as that 
would really confuse us all!

Regards,

John
---

 Now and then I run across the phrase High Noon. Can someone please 
 tell me what that means? I didn't find it in John Davis' excellent 
 glossary.
 
 Best wishes,
 
 Mac Oglesby
 -



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: time scale labels

[john . davis]

Hi Jim,

Although it would be technically incorect to use the terms Standard Time and 
Daylight Saving Time for these scales, I for one would not object as it does 
convey the meanings to th general public.  And it does serve as a 
conversation-starter for us pedantic diallists ;-).

If you wanted to avoid these terms with their precise definitions, then you 
could use Summer Time and Winter Time as approximations.  I once used the 
term Greenwich Time (rather than Greenwich Mean Time) for a horizontal dial 
which included the longitude correction and had the EoT as a graph.

Let us know what you finally opt for, please!

Regards,

John





Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Hemicyclium

[john . davis]

Hi Alexei et al,

You asked:

 on another topic, what is the difference between a hemispherium and a 
 hemicyclium?


Descriptions of both can be found in the BSS Glossary, under Dial (types of) 
at

www.britishsundialsociety.org.uk.

Regards,

John
-



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: Glossary Permission to use

[john . davis]

Hi John,

I don't see any reason why you shouldn't use extracts from the BSS Glossary in 
your pop-up windows - thanks for the compliment!  It might be reasonable to put 
a credit to the BSS and a link at one point in the screed (as an electronic 
equivalent to a footnote).  I'm happy to leave it to you to decide the most 
convenient way to do this.

I'd be interested to see which terms you choose to link to.  Some of the 
definitions are being updated in the next edition - hopefully not in a way that 
would contradict any use you might put them to.

Best regards,

John

  from:John Carmichael [EMAIL PROTECTED]
  date:Mon, 25 Nov 2002 15:12:45
  to:  [EMAIL PROTECTED]
  cc:  sundial@rrz.uni-koeln.de
  subject: Re: Glossary Permission to use
 
 Hi John:
 
 I am updating my website and my new webmaster suggested that I include a
 short glossary of those sundial terms found in my site to help people
 understand. He suggested that I keep it simple and is thinking about using
 pop up windows with the definitions when the terms appear in the text.
 
 I could write my own definitions, but I know I could never do it as well as
 you have in the BSS Glossary and I'd probably make some mistakes.
 
 Do BSS members or anyone else have permission to quote definitions directly
 from the BSS Glossary? If so, would I have to credit The BSS in each pop up
 window?  Some dialists might want to include direct links to the BSS
 Glossary, but I notice that it does not have a direct link.  To access it
 online, one must go to the BSS website and then link to it.
 
 Thanks
 
 John
 
 John L. Carmichael Jr.
 Sundial Sculptures
 925 E. Foothills Dr.
 Tucson Arizona 85718
 USA
 
 Tel: 520-696-1709
 Email: [EMAIL PROTECTED]
 Website: http://www.sundialsculptures.com
 
 
 -



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: 3-D gnomon for Polar Dial

[john . davis]

Hi Folks,

I feel that I should comment on this as it was me that initially told John 
Close that he couldn't achieve what he wanted in any simple way, when he came 
for a day's tutorial (he's a relative novice at dialling).

The problem is that a polar dial is not equiangular or have equally spaced hour 
lines.  Thus if one attempts to rotate the dial about the polar axis, the 
amount of twist has to be altered on an hour-to-hour basis, not just on a 
day-to-day one.

The solution, I think is the suggestion of Fer de Vries to use the polar dial 
designed originaly by his namesake.  This has a polar dialplate and a gnomon 
that is shaped on its UNDERSIDE, I think (from memory) that the shape required 
is a cycloid.  This was shown in the NASS Compendium a few years back.  The 
gnomon only touches the dialplate on the split noon lines with a gap increasing 
under it.  Thus the distance of the part of the gnomon that casts the 
indicating shadow moves further from the dialplate, and in the E'W directions, 
for increasing times from noon.  The hourlines are straight and equi-spaced so 
the whole dial can be rotated to account for EoT, BST and longitude.

For some reason, Fer's reply didn't seem to come to all the list members, 
though John forwarded it to me.

I will be interested to see if anyone can come up with a more conventional 
hourglass gnomon solution - I believe it is impossible (there's a challenge!).

Regards,

John
--
 Hello Frans, and sundial list members --
 
 Thanks for your interest.
 
 I apologize for any confusion caused by my use of the phrase for use 
 with straight hour lines. The words were mine, not John Close's, and 
 I guess I was trying to reinforce his desire to have a polar dial 
 which didn't use wavy hour lines, whether the lines looked like 8's 
 (full analemmas), S's (half analemmas), or stacked S's (unfolded 
 analemmas).
 
 I suggested to John that if for civil time he wouldn't use wavy 
 lines, he might pivot his dial around an axis parallel to the 
 Earth's, changing the dial's facing direction slightly every day (or 
 every few days) to account for EoT. Some dialists feel that a pivoted 
 polar is no longer a polar, but that's a different problem, for 
 polar dial seems to have some different meanings, depending on what 
 source is consulted.
 
 A 3-D gnomon on a polar dial would cast a wavy shadow on the flat 
 dial plate, and civil time could be read where that shadow crossed a 
 straight line of hour points. That is, if a suitable 3-D shape is 
 possible. Some think yes, some are skeptical, some say no. At the 
 moment, I'm in the skeptical group. What do you think?
 


Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: 3-D gnomon for Polar Dial

[john . davis]

Hi Mac et al,

You are, of course, completely right - you can turn a polar dial around its 
gnomon to make allowance for the EoT - my humble apologies.  It isn't intuitive 
(to me, at least) that this should work and I foolishly made my comment without 
experimenting or doing the maths.  I have now done so and it is quickly clear 
that the distance of the shadow edge from the noon line is the height of the 
gnomon multiplied by the tan of (hour angle plus rotation angle of the 
dialplate).

Question: does it become a declining polar dial once the dialplate is rotated?!

The mechanics of making such a dial will be interesting if it is to be robust 
enough to survive the elements.  Does anyone know of a real dial in a public 
place?

Happy Hogmanay to all diallists,

John Davis
-



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: Blenheim dial??

[john . davis]

Hi Fred et al,

I too saw this posting and contacted the chap who posted it.  From his 
description, this is definitely NOT one of the set of four dials that John 
Rowley made for Blenheim Palace c1710.

In fact, I strongly suspect that what he has is one of the 20C Pearson-Page 
reproductions.  If this is so, I would regard the Blenheim connection as 
added colour!

Regards,

John Davis
---

  from:Fred Sawyer [EMAIL PROTECTED]
  date:Mon, 30 Dec 2002 00:23:04
  to:  sundial@rrz.uni-koeln.de
  subject: Re: Blenheim dial??
 
 The following message appears on the NASS message board:
 
 From Lance Steel ([EMAIL PROTECTED]
 
 I own a sundial made of bronze and engraved 1723. It was reputedly
 liberated from the grounds of Blenheim palace, Oxford, England during WW
 II. I have been trying to find pictures of the back of the palace taken
 prior to that date to see if the sundial is there. Can anyone advise as to
 where I may obtain further information on it?
 
 
 -



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: A sundial at the rebuilt World Trade Center?

[john . davis]

Hi Bob T et al,

The analemmatic dial was being drawn by Maya Lin - she was filling-in the hour 
spots.  The caption said she was Designer - Vietnam Memorial  Presumably, she 
is relatively high-profile in the USA.

Regards,

John
---



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: Using a Dipleidscope

[john . davis]

Hi all,

I once built a declination-finder based on the dipliedoscope principle.  The 
double-view of the sun was observed through a low power telescope, using an 
eclipse filter to make this safe.

Mike is right in saying that locating the sun through the telescope is 
difficult.  I fitted a simple aperture-and-screen target finder to the top of 
the prism box to facilitate initial alignment.  I believe that with Dent's 
original devices (I've never handled one) it was a case of getting it set 
approximately to the right meridian and altitude before the time for the 
observation.

Cheers,

John

  from:The Shaws [EMAIL PROTECTED]
  date:Sun, 23 Mar 2003 09:18:01
  to:  sundial@rrz.uni-koeln.de
  subject: Re: Using a Dipleidscope
 
 I wonder if the original Dipleidscope was painted black?
 
 There is a Dent dipleidoscope in the Liverpool Museum that is painted black.
 I persuaded the curator to get it out of display for me to look at on a sunny 
 day.  
 I couldn't work out how to use it, and felt in danger of blinding myself with 
 the reflected sun.
 There must be a trick to it that I had not sorted out.
 
 If I remember correctly, Fred Sawyer showed one at the NASS conference in 
 Hartford that his daughter had made, but I didn't get to have a close look at 
 it.
 
 Mike Shaw
 
 53' 22 North
 03' 02 West
 Wirral, UK
 
 www.wiz.to/sundials 
 
 



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: Flies on sundials

[john . davis]

Hi John, Fer, et all,

I think Charles Leadbetter was an English author.  One reason that some flies 
seem large is that they are sometimes representations of dragon flies, rather 
than houseflies.  An example of this is the stained glass dial that was once in 
the chruch a Wendon Lofts, Essex.

Regards,

John
--- 



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: Construction Project

[john . davis]

Hi Tony et al,

Yes, I did some experimental dials in anodised aluminium a few years ago, 
following your excellent advice.  I haven't had the actual dials outside all 
the time, but I have had an Equation of Time plaque made by the same method on 
the south wall of my house (in the full glare of English sunshine!) for four 
years.  It's silver (natural) anodised with black lines and lettering.  As far 
as I can tell by eye, it's suffered no degradation at all.

Although the black-on-silver is close to perfect for shadow visibility, my 
customers are a very traditional bunch and prefer brass/bronze, so there's not 
much call for the anodisation.

Regards,

John
--


  from:[EMAIL PROTECTED]
  date:Mon, 07 Jul 2003 15:46:22
  to:  sundial@rrz.uni-koeln.de
  subject: Re: Construction Project
 
 Rudolf Hooijenga asked:
 
 Hello Tony and other readers of the list,
 either I was not subscribed then, or I skipped it because I was not going to
 work on aluminium,
 but I would be really interested in a repeat now. Would you please?
 
 Hi Rudolf,
   As it is a text only message I'll risk boring everyone by repeating 
 my original postings some of which were in response to other queries.  I have 
 to say that while many years ago I did dozens of projects in creative 
 anodising none of them ever included an actual sundial. John Davis on the 
 other hand has experimented with this and might wish to comment on its 
 potential in particular durability and resistance to ultra violet light which 
 was queried last time around.
 
 Best wishes
 
 Tony M.
 



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: [britishsundialsociety] A new term for The Glossary?

[john . davis]

Hi Tony et al,

Congratulations on getting a commission for a dial so far north - I am sure we 
will all be fascinated to see such an unusual dial when it is completed.

With regard to the midnight gap in the timescale, I can say that the term 
gnomon gap will appear in the next edition of the BSS Glossary.  The term 
really covers the case of vertical decliners with thick solid gnomons, where 
the gap is on the sub-style line.  But I think it covers the present case too!

Regards,

John
---

  from:[EMAIL PROTECTED]
  date:Wed, 18 Jun 2003 17:46:23
  to:  sundial@rrz.uni-koeln.de, [EMAIL PROTECTED]
  subject: Re: [britishsundialsociety] A new term for The Glossary?
 
 Fellow Shadow Watchers,
Most diallists are familiar with the Noon Gap that 
 occurs on a horizontal sundial with a thick style edge.  The fact that the 
 shadow 'swaps edges' at 6.0am and 6.0pm is also well understood.
 
 I'm currently designing a large horizontal sundial for Longyearbyen at 78° 
 12' north to be located on Spitsbergen in the Svalbard Island Group, where it 
 may well be 'the world's first heated sundial', permafrost and cabling 
 permitting.  
 
 The sun at 78°N is above the horizon for several months continuously so the 
 dial must read for a full 24 hours and its only just now dawned on me that 
 the corollary of a 'Noon Gap' is a 'Midnight Overlap'.  i.e. With a style 
 edge of any significant thickness the half hours-ish either side of midnight 
 occupy the same space on a 24 hour dial.  Of course a similar situation 
 occurs with an 'overhung' gnomon at Noon at lower latitudes as has been 
 discussed on the SML before so I should have anticipated this.
 
 Is this a new term for The Glossary or too rare to be worth listing? ;-)
 
 Tony Moss
 
 
  Yahoo! Groups Sponsor -~--
 Get A Free Psychic Reading! Your Online Answer To Life's Important Questions.
 http://us.click.yahoo.com/Lj3uPC/Me7FAA/ySSFAA/PMYolB/TM
 -~-
 
  
 
 Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ 
 
 



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m

-

Re: Sundial Carpet

[john . davis]

Hi John,

 We're also discussing what I call antiaperture gnomon sundials.  These are
 neat.  Imagine a large clear pane of clear or light colored glass on a wall.
 And on this glass is a small very dark dot. Instead of a hole in a wall
 casting a beam of light, the dark spot casts a shadow onto the sundial face.
 (John Davis, do you have a term for these?)

In my book, it's called a nodus!...

Regards,

John D


Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: Educational Presentations

[john . davis]

Hi Larry,

I have a 45-minute presentation I gave to a group of architects and an extended 
(2-hour) version for the British Horological Institute.  I'm also shortening it 
to 30-mins for the local Rotary Club next week.  No text or notes, just lots of 
pictures of the history and development of dials.

The presentations are all multi-MB and so would need to be sent on CD.

Let me know  ([EMAIL PROTECTED])if this is what you need.

Regards,

John
---
  from:Larry McDavid [EMAIL PROTECTED]
  date:Mon, 08 Sep 2003 14:08:39
  to:  sundial@rrz.uni-koeln.de
  subject: Re: Educational Presentations
 
 Does anyone have a prepared PowerPoint presentation on sundialing 
 suitable for a technical but not-dialing-focused adult group?
 -- 
 Best wishes,
 
 Larry McDavid W6FUB
 Anaheim, CA  (20 miles southeast of Los Angeles, near Disneyland)
 
 
 -



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Sudial list member

[john . davis]

Please could Canadian list member Brian Albinson contact me off-list ([EMAIL 
PROTECTED]) as I regret to say I have lost your email address.

Apologies to all other list members.

John Davis



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Spanish style sundials

[john . davis]

Dear Colleagues,

A Californian diallist who is not a member of this list wants to put a vertical 
sundial on a local church building, now used as a community centre.

The church was built in the early 1900s but to the earlier Mission-sytle.  
The wall is approximately south-facing and of white stucco.  It is likely that 
the dial will be painted onto the wall.

Can anyone point me to suitable styles of dial (probably from the 
Spanish-speaking world) that would be appropriate to the site, please.

Thanks in anticipation,

John D
--


Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: Spanish style sundials

[john . davis]

Hi Claude,

Thanks very much for taking the time to research this for me.  Martha Villegas 
has directed me to some useful sites in Mexico and it seems that there wasn't a 
single style of dials for this type of building.  So my colleague (who is a 
client for a brass dial) can let his imagination go.

Hopefully, if he completes a dial I will be able to post a picture.

Regards,

John
---

  from:Claude Hartman [EMAIL PROTECTED]
  date:Mon, 22 Sep 2003 20:02:22
  to:  sundial@rrz.uni-koeln.de
  subject: Re: Spanish style sundials
 
 I have searched for a spanish site with a number of images with little 
 success.  The best link was on the links page of the NASS site, 
 www.sundials.org/links.  The one listed as Relojes de Sol
 has a page with links to pages having images.
 
 Many of these pages show some very modern forms.
 
 I have tried to find out if sundials were used in the California missions.  
 The curators at two museums, one in Newport Beach and one at Santa Barbara, 
 could find no references.  The only sundials
 seem to be 19th century horizontals that were added in recent times.   If 
 there were ever any verticals on some walls they have either not survived or 
 have not been recognized as such.
 
 Claude Hartman
 Arroyo Grande, California
 
 [EMAIL PROTECTED] wrote:
 
  Dear Colleagues,
 
  A Californian diallist who is not a member of this list wants to put a 
  vertical sundial on a local church building, now used as a community centre.
 
  The church was built in the early 1900s but to the earlier Mission-sytle. 
   The wall is approximately south-facing and of white stucco.  It is likely 
  that the dial will be painted onto the wall.
 
  Can anyone point me to suitable styles of dial (probably from the 
  Spanish-speaking world) that would be appropriate to the site, please.
 
  Thanks in anticipation,
 
  John D
  --
 
  Dr J R Davis
  Flowton Dials
  N52d 08m: E1d 05m
  -
 
 
 -



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Gnomons and screws

[john . davis]

Dear dialling colleagues,

I'm helping to restore a Richard Melville (worked 1832-1871) slate dial with 
multiple gnomons.  The gnomons are held in with 2BA brass screws using square 
nuts.  The gnomons themselves are nominally 1/4 inch thick but with 
considerable variation, i.e. not the modern rolled plate accuracy.

Can anyone tell me when the BA (British Association) screwthread standard 
started?  I think it points to the gnomons being (old) replacements.

Regards,

John Davis
-


Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

Re: Gnomons and screws

[john . davis]

Hi Mike,

I've had responses that indicate that Melville used a variety of methods to 
attach gnomons, from leading them in, fitting them with flanges underneath to 
the twisted tenons that you mentioned.  No 2BA screws, though!  So I am 
convinced that the ones on the Dunmore (Ireland) dial are replacements.  If you 
have a picture of the actual shape of an authentic Melville gnomon, that would 
be useful - thanks for offering. (I have the one of the Salisbury dial that 
Nick Nicholls published in 1995).  Otherwise, we will just re-fit the existing 
replacements which are acually quite reasonable.

Regards,

John
--



Dr J R Davis
Flowton Dials
N52d 08m: E1d 05m
-

BSS Sundial Glossary - 2nd Edition

[JOHN DAVIS]

I'm pleased to announce that the Second Edition of the British Sundial Society Dialling Glossary is now available. Now subtitled "A sourcebook of dialling data" to reflect its expanded scope, it is about twice the size of the original with 84 pages, far more illustrations, a section on biographies and 29 Appendices of data invaluable to all diallists.

The printed version is available from BSS Sales (Margery Lovatt on [EMAIL PROTECTED]). The price, including post and packing is 15 UKP (UK): 17 UKP (Europe): and 19 UKP (Rest of World). The BSS can now accept payment by credit card and by dollar cheques (from a US bank). Contact me for details.

There are no immediate plans to produce an electronic version (either online or on CD) of the Second Edition. The BSS may eventually do this, but it won't happen for a while.

My thanks go to all the diallists who contributed to the Glossary. I hope everyone is mentioned in the Acknowledgements but my sincere apologies if I have missed anyone.

I am still collecting useful dialling information, and corrections to existing definitions, so please contact me if you have any ideas for a Third Edition - though it could be many years before it gets published.

Regards,

John
-
Dr J R DavisFlowton DialsN52d 08m: E1d 05m

Re: Anniversary-of-a-date dial

[JOHN DAVIS]

Perhaps the classic "anniversary" dial is the vertical decliner by Christopher Daniel at Chatham, Kent. It is known as the Nelson dial and it has a small circular spot in the dialface in the form of the Union Flag. This commemorates not just the date, but also the time when Admiral Nelson was mortally wounded on his flagship HMS Victory during the Battle of Trafalgar.

Regards,

John
---Dr J R DavisFlowton DialsN52d 08m: E1d 05m)

Re: Inferior Polar Dial

[JOHN DAVIS]

The Wolsey/Kratzer dial is discussed in Peter Drinkwater's booklet "The Sundials of Nicholas Kratzer". Although he doesn't analyse the hourlines, it is clear that Drinkwater is no admirer of Kratzer's dialling abilities - he accuses him of all sorts of muddles and mistakes.

The "6" marking on the sub-style line sounds like an attempt at usingItalian hours, measured from sunset. But that couldn't be correct. Can you tell from the picture whether the dial is read from the shadow of the tip of the gnomon (as was common on Kratzer's dials) or from its whole length?

Obviously there is a need to look at the dial closely in April!

Regards,

John
--[EMAIL PROTECTED] wrote:
On 25th Jan I posted the following query:What hour lines should be inscribed, and in what places, on an inferior polar dial for latitude 52N? The centrally-placed gnomon is 13 units high, the overall plate width (east-west) is 37 units and the north-south plate height is 26 units.Thank you for the various replies sent in (4).I clarified the term 'inferior' later on that day thus:"Inferior"..Think first of a 'normal' polar dial, parallel to the polar axis, aligned E-W but face open to the south i.e. that part of the celestial equator above the horizon. Now consider the underneath of this polar dial, face open to the north, facing that part of the celestial equator which is (mostly) below the northern horizon. You've now got an 'inferior' polar dial. Th!
 e term is
 used in a document I came across recently (on the internet). I suppose that an equivalent description would be 'a polar dial facing north' or a direct north dial inclining at an angle to the horizon equal to the latitude of the place (52 deg in this case). Yes - it will be latitude independent, but I included that detail so that it would pin down the discussion a bit.The BSS Glossary also defines 'inferior' as "refers to an event on the celestial sphere below the horizon. Opposite of superior."Let me now tell you the reason for my enquiry:I was looking at the website of the Museum of the History of Science, Oxford (epact.mhs.ox.ac.uk/catalogue), and brought up the details of Nicolaus Kratzer's portable polyhedral dial (1525) made of gilt brass which he presented to Cardinal Wolsey (Inventory No. 54054). It appears to have been made for latitude 52 deg. NThere are dials on nine faces. One is described as an 'inferior polar dial, with lines marked 4,6,!
 8. This
 puzzled me - what is the sense of only hours 4,6,8 on any dial?The illustration given on the museum's web page is not clear enough to get any detail other than to see that the north face is not visible. However, a postcard I bought at the museum some years ago does show the north face and knowing the overall height of the dial (100mm) I estimate that the height of the gnomon on the inferior polar dial is 13 mm. It seems that the lines for 4 am ( to the west and 8 pm to the east) are wrongly positioned - they should be about 22.5 mm away from the centre of the dial, and are nowhere near this distance.A further puzzle - why did Kratzer mark the line on which the gnomon lies with a 6? It should be 12 (midnight!) if it's going to be anything - or was it because 6 comes exactly between 8 and 4? A blunder, perhaps?More measurement pending..David BrownSomerton, Somerset, UK Dr J R Davis!
 Flowton
 DialsN52d 08m: E1d 05m)

Re: mass-produced dial

[JOHN DAVIS]

The cast vertical dial with medieval figures you describe was made by Pearson Page c.1931, catalogue number 4212. Their catalogue was illustrated in the Bulletin of the Scientific Instrument Society No.3, pp10-11, 1984. and also in No. 5.

I am not sure if your "clown" dial was made by them too - the illustrations in the SIS Bulletin are not very clear. I suspect it may be by them. If you could send me the picture, please, I will try to match it up with the catalogue.

Regards,

John Davis
-Frank Evans [EMAIL PROTECTED] wrote:
Greetings fellow dialists,In the current BSS Bulletin, p.77, Member A. Capon describes a mass-produced cast metal vertical dial of good quality, citing seven examples he knows of, five of which he has seen personally. The dial, elaborately decorated with the arms of what appears to be an English medieval monarch (helm, barred, afronty; supporters, lions rampant, no unicorn) and half a dozen medieval figures in a colonnade, is figured on the front cover of the Bulletin, March, 2003 and there is a good picture in February 1996, p.7.He might like to know that another of these dials, which he does not list, is to be found in the famous National Trust garden at Sissinghurst Castle in Kent. It is recorded as SNRO 0602. There are more. As well as Sissinghurst I have seen one elsewhere but am bothered to recall where. Any further
 contributions?And has anyone any information about another good quality mass-produced cast metal dial showing a man's (a clown's?) head bursting through a paper hoop and with a tin whistle in his mouth which forms the gnomon? There is an example on a front door in Worthing, Sussex and I have seen a picture in a book somewhere, but once again cannot remember where. I can forward a picture of this dial (about 80 kb) to enquirers.Frank 55N 1W-- Frank Evans[EMAIL PROTECTED]-Dr J R DavisFlowton DialsN52d 08m: E1d 05m

BSS Glossary,Fourier series and declination

[JOHN DAVIS]

As Editor of the BSS Glossary, I must humbly apologise for not giving the source of the Spencer fourier series which John Pickard very kindly made me aware of. I have no real excuse, other than a poor memory and that it would have been impossible to quote the source of all the information in the Glossary, though clearly this case could have been an exception.

By coincidence, the Second Edition of the Glossary is currently at the printers - I expect to have copies available at the BSS International Conference in Oxford next month. 

Soon after the First Edition was published, Gianni Ferrari kindly contacted me with a number of corrections and improvements. These have finally been incorporated into the Second Edition. They include the equations for declination and EoT which Gianni mentioned in his posting, and the tables of averaged values for the first half of the 21st century. I have remembered to credit Gianni for supplying these this time. It seemed worthwhile replacing the Spencer equations in the light of the more recent expressions, though I intend no disrespect for Spencer.

The Second Edition Glossary is twice the size of the original, at 88 printed pages.It is now sub-titled "A Sourcebook of Dialling Data", includes far more illustrations, definitions, and a section on biographies.It is not currently planned to produce an on-line version, simply because of the work involved in producing a web-compatible version. Bob Terwilliger did a tremendous job on the first edition but it would be unfair to expect him to do it again. If I ever get fed up with actually making dials, I might learn how to do it myself!

Regards,

John Davis
-John Pickard [EMAIL PROTECTED] wrote:
Gianni and others,As a long-time academic and scientist, I am acutely aware of the principlesand practice of giving credit for previous work. Given the recent exchangeson calculating declination, I have sent a copy of Spencer's original paperwhere he published for the first time the Fourier series for declination andEoT. I had posted this to the Sundial List several years ago, but in aslightly different format. I assume this is the origin of the entry in theBSS Glossary.I am sure that no disrespect was intended when the BSS Glossary wascomplied, but it would be nice if these equations were quoted as coming fromSpencer. In science, this is polite, expected, and considered basic goodpractice. Doing otherwise is commonly known as plagiarism at worst, badmanners at best.One reply I have received in the last day or so!
  said
 that he had alwayswondered at the source of the Fourier series for declination. He now knows.By giving the sources of equations, etc. (unless they are lost in the mistsof time), people can track back to the original publication and check themathematics or logic used to derive the information. In the case of theSpencer equations, reading the original paper in the (now defunct) journalSearch would NOT pick up a typographic error in one of the equations. Thiswas noted as an erratum in a subsequent issue of the journal. However, Ihave made the correction in the version I posted a day or so back.It would be nice to see the work of Spencer remembered in the BSS Glossary,perhaps as "the Spencer Fourier series to calculate declination and EoT".Cheers, John[EMAIL PROTECTED]Dr J R DavisFlowton DialsN52d 08m: E1d 05m

Re: azimuth dial

[JOHN DAVIS]

I was intrigued by the description of the Richard Whitehead dial in the BSS Register so I'm glad that you are investigating it. Whitehead was apprenticed to my hero Henry Wynne, who's large double horizontal dials feature azimuth scales. The one at Wrest Park (Bedfordshire) has an azimuth scale divided down to one-eighth points, as well as to quarter degrees.The points are labelled, for example, SWbS.Slightly later dials of similar size (about 750mm diameter) by Wynne seem to make do with quarter points and half degrees. Most of the other information on the dials is astronomical, rather than nautical.

By coincidence, I am currently designing a dial for an Americal client which willinclude a central pin to show the azimuth of the sun, particularly at sunrise/sunset. In this case, the gnomon will be of the cantelevered or underslung type where the shadow is cast by the bottom edge of the gnomon. This leaves the centre of the dialplate clear for the scales.

I would be interested to see how Whitehead arranged his shadow pin for the azimuth scale. Do you think it was an actual pin rather than a plumb-bob or plummet?

Regards,

John
-Frank Evans [EMAIL PROTECTED] wrote:
Greetings Fellow Dialists,I am interested in a pedestal dial in the English Lake District. My interest is in the arrangement for finding the azimuth of the sun. The dial is by Richard Whitehead, dated 1688, and a central compass rose is divided into points, the points being further divided into one eighths i.e. better than 1.5 degrees. The gnomon is vertically drilled for a central shadow pin, which is missing.Does anyone have any information about shadow pins in sundials and are there other examples of dials centrally inscribed in points with the object of finding the sun's direction. And were points an essentially nautical feature?The dial was first listed in the BSS Sundial Register, No,  in Cumbria, by Robert Sylvester.Frank 55N 1W-- Frank Evans[EMAIL PROTECTED]-Dr J R
 DavisFlowton DialsN52d 08m: E1d 05m

Moon transits

[JOHN DAVIS]

A colleague who is writing an article on moondials has asked if there is a website which gives the times of the moon's transit on a daily basis, and preferably from the user's location. Any offers?

Regards,

John Davis
-Dr J R DavisFlowton DialsN52d 08m: E1d 05m

Re: Wall Declination Measurement

[JOHN DAVIS]

Gianna got in before me with the answer to your question.

I use a version of the "nail in a board" method myself. I like to take several measurements, preferably over a couple of hours, to improve the accuracy of the measurement. As well as the horizontal position, I also record the vertical position of the shadow tip below the base ot the "nail". This can be compared with the sun's altitude and proves a useful double-check, allowing doubtful readings to be discarded.

Regards,

John
--John Carmichael [EMAIL PROTECTED] wrote:




Hello Carol: (c.c Sundial List)

I'm back home and this morning I'm looking at your wall declination measurements. Unfortunately, I am not accustomed to using the nail method you used and I hesitate to comment because I don't want to make a mistake. I have heard of this method however. I am going to forward your letter to our Sundial List discussion group and hopefully somebody there will be able to check your measurements.

But I was able to check your solar azimuth data that you got from your astronomy program. According to the program I use (The Dialist Companion), the solar azimuth at that latitude, longitude and time was about 20.45 degrees west of south, not 209 degrees. Just think about it. If the solar declination were 180 degrees west of south, the sun would be due north and that's not possible. 209 degrees would be towards the North East which is also impossible.

Hopefully, somebody from the sundial list will help us.

John

- Original Message - 
From: carol arnold 
To: John Carmichael 
Sent: Monday, November 22, 2004 1:09 PM
Subject: declination

John, I was just having a go at measuring the declination of a window in my house - I am not convinced of the accuracy of my measurement of sun angle to wall,but I wondered if you could double check the calcualtions? The window was approx south facing.

22 nov 2004 at14.01 gmt
I used a nail 92mm long on a vertical board and its shadow was 50mm to the right of the nail. So the sun angle to the wall is 28 deg 31min 23sec west of south.
My astronomy program gave me azimuth of sun to be 209 deg 44min 31sec ie 29deg 44min 31sec west of south, for lat 51deg 25min 20sec North and long 2 deg 42 min 30 sec west.
So I reckon the the wall faces 1 deg 13 min 8 sec west of south??

Regards and hope you dont mind my asking you about this,
Carol

Carol Arnold
Stained glass artist, commissions welcome,
please takea look at my stained glass websitehttp://www.carolarnold.co.uk


Moving house? Beach bar in Thailand? New Wardrobe? Win £10k with Yahoo! Mail to make your dream a reality.Dr J R DavisFlowton DialsN52d 08m: E1d 05m

Re: dial security

[JOHN DAVIS]

You're right to think that any 17th century dial is at risk if left outside - not just by theft but also by continuing erosion by acid rain.

The correct thing to do is to move the original dial inside the house where it can be properly secured and looked after. It could be replaced outside by either a replica or a copy/reproduction:-

replica: an exact copy made by making a silicone mould from the original and using that as a basis for moulding a bronze/brass resin version.

copy or reproduction: redesigned and made from scratch in brass/bronze, using measurements and photographs of the original as the basis for the design.

The former is likely to be cheaper but not as long-lasting as the latter. The replica will match the existing condition of the original (down to the smallest scratch) but the colour of the patination is difficult to match exactly. The reproduction/copy will look more like the original did when it was new.

At the risk of posting a commercial, I could produce either form if required!

Regards,

JohnFrank Evans [EMAIL PROTECTED] wrote:
Greetings fellow dialists,I am seeking advice about a country house pedestal dial of the seventeenthcentury. It is a valuable dial by a known maker and stands in the estategrounds, which are open to the public. The administrator of the estate isaware that the dial is at risk of theft and has asked for advice. EnglishHeritage (an official body) have been consulted. They felt that the dial wasin its "proper place" and should not be moved but they, too, felt the riskof theft was present.The administrator has asked me to advise them and is aware that some costwould accrue in protecting the dial. They wonder, perhaps, whether a copymight be created and what would be involved. Or any other suggestion thatwould be helpful.Can anyone help? If you would prefer to send me a private message that wouldbe OK.Frank 55N
 1W[EMAIL PROTECTED]---Outgoing mail is certified Virus Free.Checked by AVG anti-virus system (http://www.grisoft.com).Version: 6.0.749 / Virus Database: 501 - Release Date: 01/09/2004-Dr J R DavisFlowton DialsN52d 08m: E1d 05m

Re: The Merton Church Dial

[JOHN DAVIS]

Merton (near Watton, Norfolk) isn't too far from me so I'll try to get along there. Churches are often locked these days so I will try to make a contact first.

Watch this space..

Regards,

John
-John Carmichael [EMAIL PROTECTED] wrote:





Boy am I having a good day! I think I've just found the lost Merton Church stained glass sundial that was also in the Behrendt Videotapes and article.It's located at St. Peter's Church in Merton, Norfolk England.
I saw this website ( http://www.wayland.org.uk/site/site/Merton/church) and buried in the website text is this sentence:
"A curiosity will be found in a south aisle window. It is a representation in stained glass of the passing hours with a Latin tag, suggesting that "while we talk time flies", and in the corner a spider is busy catching a fly."
In Behrendt's article he says that it's latin motto says ""dum loquimur fugit hors" , and I'm pretty sure this translates into "while we talk time flies".
So that proves it. It is the missing Merton ChurchDial!
Even in our horrible photograph you can see that it's quite beautiful.
I'm hinting that we need better photos of this one too. Do any of you live in Norfolk?

(By the way, I'm confused if Merton is the town or if Wayland is the town in Norfolk.)Dr J R DavisFlowton DialsN52d 08m: E1d 05m

Re: Wappen

[JOHN DAVIS]

I have included coats of arms on a number of brass sundials that I have made. You can see some pictures of a few of them on www.flowton-dials.co.uk If you want to see others, or larger pictures, contact me directly.

Regards,

John Davis
Fred Jaggi [EMAIL PROTECTED] wrote:
I have a Swiss family wappen (coat of arms ) which I would like to includein a sundial. I'm not an artist so I would like to see some examples ofcoats of arms included in sundials. Does anyone know of anyFred Jaggi-Dr J R DavisFlowton DialsN52d 08m: E1d 05m

Gnomon location holes

[JOHN DAVIS]

A couple of months ago, Mike Cowham asked the SML for an explanation of the two small dots or holes seen on the dialplates of antique horizontal dials, just where the tip of the gnomon meets the dialplate. Several suggestions were made, such as their use as alignment marks to position the gnomon. Tony Moss made the suggestion that they acted as location points for a swivelling straight-edge which was used to mark out the hourlines. 
I have recently come across a picture of a c.1700 declinatory by John Coggs which gives support to Tony’s suggestion. This small instrument consists of a circular horizontal dial which is free to rotate on a larger square plate with a protractor scale. As befits a portable instrument, the gnomon has the facility of folding flat. The resulting hinge mechanism means that the southern tip of the gnomon is truncated and it thus stops just short of the VI-VI line. BUT, the two holes are clearly visible at the origins of delineation. Since the holes cannot, in this case, be used to position the gnomon correctly, it seems highly likely that they were part of t!
 he
 delineation process.
When were these holes first used? Very early (before 1600) horizontal dials usually had very thin gnomons and no evidence of the holes. Elias Allen’s double horizontal dials in the 1620-1650 period do have them.
Can anyone give other examples of early dials with these “delineation origins”.
Regards,
John DavisDr J R DavisFlowton DialsN52d 08m: E1d 05m

Re: Magnetic Gnomon Attachment

[JOHN DAVIS]

John,

Bill is right to query this - a magnet won't attract non-magnetic stainless steel (by definition!). I think there may be varieties of stainless whichARE ferromagnetic but the attraction may not be as strong as ordinary steel.

Regards,

John
--John Carmichael [EMAIL PROTECTED] wrote:
- Original Message - From: <[EMAIL PROTECTED]>To: <[EMAIL PROTECTED]>Sent: Tuesday, February 01, 2005 11:36 AMSubject: Re: Magnetic Gnomon Attachment John, is Stainless Steel magnetic? - BillNo, but the magnet is. And a magnet will attract it.Of course, insead of one piece of steel and one magnet, you could use two magnets for double the holding strength!What neat is that the magnet will aslo work at a distance, THROUGH the glass!Dr J R DavisFlowton DialsN52d 08m: E1d 05m

Re: Porcelain Sundial Faces

[JOHN DAVIS]

 uropean
 firm called Vitramet who arranged for the enamelling to be done in Mexico - a very large furnace was needed!The story of the dials is in the Bulletin of the British Sundial Society, September 2004.Regards,JohnJohn Carmichael [EMAIL PROTECTED] wrote:




Hello all:

I've been investigating the best and most durable materials for the sundial faces of my sundial cupola design.

I've discovered this:

1.Even the bestenamel paints chip, wear off and fade.
2. Baked powder coat paints are much more durable but you can not easily paint more than one color or a design on top of another color.You can not overglaze, (put another layer of powdercoat over a base layer).
3. Porcelain has a great advantage in that it can be overglazed with different colors of vitreous paints and refired. So porcelain painting is similar to glass painting in that you can paint it with a permanent overglaze of different colored paints that do not fade, chip or flake off. It's practically weather-proof!

Many old clock faces were madeon painted porcelain for these very good reasons.

There are companies who will paint and fire your sundial design on porcelain. They can make stencils from your design drawingsor they can paint by hand. I even found one company that has a photographic technique of applying paint to porcelain. (and it's here in Tucson!)

Have any of you ever seen a painted porcelain sundial?

Here are a couple of good websites about porcelain painting (also known as "china painting").

http://www.china-painting-list.com/fullsrch.html
http://www.porcelainpainters.com/
http://www.porcelain-industries.com/porcelain-industries/porcelain-industries.htm

John L. CarmichaelSundial Sculptures925 E. Foothills Dr.Tucson AZ 85718-4716USATel: 520-6961709Email: [EMAIL PROTECTED]

My Websites:Sundial Sculptures: http://www.sundialsculptures.comStained Glass Sundials: http://www.stainedglasssundials.comDr J DavisFlowton Dials

Statue and sundial

[JOHN DAVIS]

Dear Dialling Colleagues,

A non-member of the List has asked me to forward this question:

"I have a picture of an 18th century print of a plaster and lathe arch which was constructed to celebrate an election victory on Worcester [UK], replete with symbolism and classical references. On one side of the pediment is a statue of a female figure leaning against a pedestal with a sundial on top. The statue is paired with one of Liberty (blindfolded and with scales of justice) on the other side. I wonder if the sundial statue might be of Clio. Do any of your sundial collegues know of similar classical statues with sundials, who the figure might be, or what is symbolised?"

I have a small (9kbyte) jpg of the print which I can forward to those interested (though the sundial is only just visible.

Regards,

John
Dr J DavisFlowton Dials

Re: Wilkins

[JOHN DAVIS]

There is no "F Wilkins" in Jill Wilson's Biographical Index of British Dialmakers nor in Gloria Clifton's Directory of Scientific Instrument Makers. It is possible that he was a clockmaker or, just possibly, the dial is a fake. Is there any chance of a picture?

Regards,

John
---tony moss [EMAIL PROTECTED] wrote:
Fellow Shadow Watchers,I've been contacted by an Edinburgh client who described her old dial as being marked:F. WILKINS LONDON with no further added details.Does anyone have more details of this maker please?Tony Moss-Dr J DavisFlowton Dials

RE: Sundial mottos for clergy

[JOHN DAVIS]

Hi Jim et al:

The motto which the Bishop of Ely requested for the dial I made for him was:

"Now is the acceptable time: now is the day of salvation"

I think this is a biblical quotation. Not to my taste, but then the customer is always right!

Regards,

John Davis
---Dr J DavisFlowton Dials

Re: tried hard anodizing?

[JOHN DAVIS]

Hi John,I tried some home-made anodising a few years ago, and I also used some pre-formed anodised sheets (with photoresist already applied). One item I made was an Equation of Time plaque which has been on the south wall of my house for about 4 years and still looks exactly as it did when I put it there. The surface is a semi-matt silver, with black lettering, embedded into the anodised layer, which everyone told me would fade but hasn'tyet! The "World Dial" which I made for Heiner Thiessen (http://www.solardials.com/solardials.html) also used pre-anodised aluminium.Regards,John D  ---[EMAIL PROTECTED] wrote:  Has anyone tried hard anodizing? I used to use tefloned hard anodizing on 6061 for mechanical parts subject to sliding. It has a duller, grayer finish. I wonder how it does in the weather. I have regular anodizing, water sealed, on my 12" (30 cm) bowstring equatorial. Fine weather resistance, but... The equatorial surface is really a concave cylindrical mirror, so it's pretty darn bright to the eye from some norrmal viewing positions. Hard anodizing might be the cure. Anyone tried it?For those unfamiliar with hard anodizing, but curious, googling found:http://www.techplate.com/hard_anodize.htmThanks,John B---https://lists.uni-koeln.de/mailman/listinfo/sundialDr J DavisFlowton Dials---
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Re: AW: tried hard anodizing?

[JOHN DAVIS]

Hi Hannes,The pre-anodised aluminium sheets that I have used go by the trade name of Gedakop in the UK. The manufacturers anodise aluminium sheets (of various thicknesses) by the normal methods but don't seal the pores. They apply a photoresist layer and then put on a black protective plastic before shipping.To use the panels, the plastic sheet is removed in subdued light and a transparent photomask (with a positive image) is exposed with UV. This is preferably done in a vacuum UV lightbox but can use the sun! The unexposed resist is then washed away with a water jet. The exposed pores of anodising are then coloured with a special ink which is wiped over the surface. The ink embeds itself into the pores of the anodisation. The remaining resist is then removed with a thinner. Finally, the panel is sealed, closing the pores and locking the ink in, by boiling in
 water with an additive for a few minutes.The process can be a bit tricky to get used to but it does produce quite professional and long-lasting results with a minimum of equipment.Good luck if you try it!John D.  --hannes [EMAIL PROTECTED] wrote:  John (D),you talk about pre-anodised sheets with photoresist applied. is this anodising applied or removed by a photographic process? how does it work? how do you make the color change?sounds like a very intresting material for our purposes!hannes--hannes
 kühtreiber[EMAIL PROTECTED]http://www.datenmull.at.tf---https://lists.uni-koeln.de/mailman/listinfo/sundial---
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Re: Oxford college sundial

[JOHN DAVIS]

Hi Bob,Thanks to pointing everyone to the story in today's Daily Telegraph about the possible re-siting of Christopher Wren's All Souls', Oxford, dial. The story (which was in the June BSS Bulletin) is particularly important today as I believe a decision may be announced. I've also been told that BSS member Tony Ashmore, who lives near Oxford, is being interviewed by ITV television about it this afternoon (Monday). I'm not sure if it will be broadcast on the local or national news!Regard,John Davis  -Robert Terwilliger [EMAIL PROTECTED] wrote:  Don's bequest decided by a sundial 
   http://makeashorterlink.com/?I17962F3D---https://lists.uni-koeln.de/mailman/listinfo/sundial---
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Re: Giant Cone Gnomon?

[JOHN DAVIS]

Hi John C,That's a BIG gnomon! It will be enormously heavy if it is solid so I would opt for a fabricated design. Although you can make a cone by rolling up a circle with a slice cut out, that would need a sheet of material large enough to draw at least part of a 24' diameter circle - not easy to come by.As an alternative to a circular cone, how abouttapered cylinderbased on a regular polygon for the cross-section? The base could be, for example, a 20-sided polygon and the sides would be 20 long, thin isosceles triangles, 12'+ tall. You could either get a sheet metal worker to weld it up, or make it out of fibreboard and soak the surface with epoxy resin. For stiffness, you might need a series of progressively smalled polygons distributed up a central rod to form a backbone and ribs to the structure.   
 Sounds like an interesting project - how robust is the client's budget?Regards,John D  -John Carmichael [EMAIL PROTECTED] wrote:  Hello All (esp. sundial makers):I needsome helpon something. (what else is new)...I'm designing a huge horizontal dial for Cordera Elementary School in Colorado Springs. The face is 120' wide and the perpendicular gnomon will be 12' (3.65M) tall. I'd like to talk the
 builder into using a giant cone gnomon, but I have no idea how in the world you would construct one!I don't think I have ever seen a giant cone gnomon on a monumental sized sundial. Would it be easier to make it out of concrete poured in a mold, bent sheet metalor some other material?Any ideas Tony or anyone?Maybe I could find a surplus rocket nosecone somewhere!Do you think it would be really difficult and expensive to fabricate a giant cone?If we can't use a cone, we will have to use a blunted pyramid (obelisk) instead.thanks for any ideas,John---https://lists.uni-koeln.de/mailman/listinfo/sundial---
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Re: Slanted Roman Numerals

[JOHN DAVIS]

Hi Carl,
   
  On traditional English horizontal dials, the Roman numerals are not only 
slanted along the hour lines but also have their tops and bottoms as circular 
arcs, centred on the middle of the dialplate rather than the origins of the 
hour lines.  Thus, although programs such as Illustrator can, I think, slant a 
piece of text I prefer to draw each numeral separately as a set of polygons, 
arcs etc. in my CAD system.
   
  Different London makers in the 17th and 18th centuries had different 
conventions of what part of the numeral was aligned along the hourline.  So, 
for example, with the numeral 'II' for two o'clock, there is a choice of 
running the hourline through the gap between the two 'I's or up the inside edge 
of one of them.  For the numeral 'V' (five o'clock) the choice in the early 
period was to bisect the angle of the V with the hourline.  Later on, the two 
arms of the Vs became less widely spread and the width difference between the 
thick and thin strokes was more pronounced. In these cases, it became common to 
slant the numeral so that the hourline runs along the narrow stroke.
   
  The techniques of drawing these numerals depends on the CAD package used.  
With TurboCAD, I use a combination of a wide-ish single line for the narrow 
strokes and a faint double line (later removed) to define the wide stroke which 
is then filled in with a solid polygon.  Niceties such as tapering narrow 
strokes, serifs which are chamfered to the verticals etc. and which are found 
on the elegant late 18th century dials are added afterwards.
   
  I hope this helps!
   
  John
  

Carl  Barbara Sabanski [EMAIL PROTECTED] wrote:
  Sunny Day!

I have noticed on a number of different sundials that the Roman numerals
used for the hour numbers are sloped to match the angle of the hour line.
Is a special font, technique or combination of the two used to do this? I,
and I am sure others, would be very interested in learning how to do this.

Thank you for your help!

Happy Dialling!

Carl Sabanski
www.mysundial.ca

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Re: strange longitude

[JOHN DAVIS]

Hi Frank et al,
   
  That's an interesting one!  I make Hawkshead about 3 deg. W of Greenwich so 
assuming the second figure is a longitude difference, that would put the 
location as approx 38deg 44' E or 32deg 44' W relative to the Prime Meridian.
   
  My first guess was that an eastern location was the most likely, with 
Jerusalem or Constantinople (Istanbul) being the places most commonly found on 
dials or old maps.  But Jerusalem is 35deg 10' and Constantinople is only 
29deg.  Old longitudes are often wildly inaccurate but by 1845 they should have 
been within a few arcminutes.
   
  The PL initials are new to me - how about 'Palestine' or some varient?
   
  Nowhere is South America or Greenland looks attractive for an eastern 
location.
   
  So I'm stumped for the moment!
   
  Regards,
   
  John
  

Frank Evans [EMAIL PROTECTED] wrote:
  Greetings, fellow dialists,
Reference the sundial on the Old Grammar School, Hawkshead, Cumbria, 
England. The school is a museum, famous as the place of William 
Wordsworth's education. Over the door is a fine dial dated 1845 with 
stated co-ordinates, latitude 54 deg. 22 min. 10 sec. and longitude 
PL 35 deg. 43 min. 40 sec.

The latitude appears to refer to the correct location but the longitude 
is a puzzle which the museum curator was unable to explain. Longitude 
eastward of Greenwich lands in an unremarked location in the middle of 
Russia but westward takes us close to Recife, formerly Pernambuco, 
Brazil. No significant place on the coast there (lighthouse, etc) fits 
but I am wondering if there is or was an observatory in or near the 
middle of the town. And what can the letters PL mean?
Any suggestions for this strange longitude citing?
Frank, 55N 1W

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Re: Porcelain Sundials

[JOHN DAVIS]

Hi John and sundiallists everywhere,
   
  You might be interested to know that Harriet James and I are currently making 
a vitreous enamel on steel dial to replace an art-deco painted steel dial on a 
private house.  The original iron scrollwork gnomon will be reused.  The firm 
doing the enamelling are called Vitramet - they also did the set of four large 
vertical towers dials I designed for Houghton Hall in Norfolk.
   
  During the BSS Cambridge Conference we all admired the set of 6 dials on the 
Gate of Honour at Gonville  Caiuis College.  These were enamelled in the 
1960s, I think, by a firm in Birmingham who seem to have disappeared now.
   
  Regards,
   
  John Davis
  

John Carmichael [EMAIL PROTECTED] wrote:
st1\:*{behavior:url(#default#ieooui) }Dear Frank (cc 
Sundial List):
   
  I just wanted to tell you how much I enjoyed seeing you and getting a chance 
to talk with you at the conference, especially our discussions about the 
possibility of using durable fired porcelain instead of paint for the 
replacement of old deteriorated painted sundials.
   

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Re: Porcelain Sundials

[JOHN DAVIS]

Hi Frank et al,
   
  The Houghton Hall sundials were made by Vitramet Europe Ltd. 
(http://www.vitrameteuropeltd.com/).  I notice that one of the dials actually 
features in the photomontage that heads their homepage.
   
  Although Vitramet have some facilities in the UK, the Houghton Hall dials 
were actually enamelled in Mexico(!) because of their size (1320mm diameter or 
around 53.5). I only had to deal with the UK office, I'm pleased to say.  I 
don't know how much bigger they could go. One nice feature is that the gold 
lines feature real gold particles which are ground up in the paste enamel and 
then fired in - they do have a cheaper option though!
   
  One of the dials (the N face) had to be in two pieces to allow it to be 
assembled around the original 1727 gnomon which is fixed into the stonework 
behind the dial.  Thus if you wanted to make a dial which was bigger than 
Vitramet's oven, it would be possible to assemble it from separate panels 
mounted edge-to-edge.
   
  Regards,
   
  John D
  --

Frank King [EMAIL PROTECTED] wrote:
  Dear Patrick,

Your short message is a mine of information...

  I am fairly sure they (the dials on St Margaret
  of Antioch's Ch) ARE enamel!

You are quite right to refer to this place as the
Church of S. Margaret of Antioch and, likewise, I
should have referred to the Collegiate Church of
S. Peter in Westminster rather than the vernacular
Westminster Abbey! I must try harder!

As far as I know, the latter has no dials (though I
put one in the street close to its Chapter House)
whereas the former has four.

Even more interestingly you say:

 Yes, they are enamel
 They are huge too - 8ft 6ins in diameter.

This measurement raises further questions. John
Carmichael explained that the biggest oven that
his suppliers use will accommodate a maximum size
dial of 46 square.

The Margaret of Antioch dials are over twice that
size. I wonder whether Brookbrae could still do
a job that big. If so, they may have a customer!

Frank

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RE: Porcelain Sundials

[JOHN DAVIS]

Hi John C, Patrick et al,
   
  Chris Daniel once told me that the hour lines on the St Mary's Westminster 
dials are platinum leaf.  Harriet James says that it's even worse to work with 
than gold leaf!
   
  Re gold in vitreous enamelling: the gold powder floats to the surface during 
kiln firing so you end up with a glass-protected solid gold line.  Wonderful - 
but expensive!
   
  Regards,
   
  John D
  ---

John Carmichael [EMAIL PROTECTED] wrote:
  
Now this raises one more important question. Note that the hour lines and
the numerals are shiny gold on a blue background. The blue color is
certainly baked on powder coat enamel. But what is the gold color? Is the
gold color gold leaf that was applied by hand on top of the powder coat blue
background, or is the gold color also powder coat? If you talk to Chris
again, could you ask him?

John

p.s. this question is important because if the gold color is powder coat, it
would probably double the cost because each color requires a separate baking
in the oven and a different stencil. You can not bake on two colors at the
same time. Also, gold powder coat paint probably is not as shiny as gold
leaf. 


As we discussed, it is hard to have very large kiln-Original
Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Patrick Powers
Sent: Tuesday, April 24, 2007 12:58 PM
To: 'Sundial List'
Subject: RE: Porcelain Sundials

Message text written by Patrick Powers
I shall ask Chris Daniel (who is not a member of this list as far as I
know) about what he thinks the finish was on St Margaret's.

Well, I did ask Chris Daniel about the St Margaret of Antioch dials and he
confirms that they were stove-enamelled - like my Morris Cowley mudguards
and not vitreously enamelled. This stove enamelling process gives a more
flexible finish but the colour is a fired paint and is not made from fused
glass particles and the paint is sprayed on using electrostatic attraction
to give better adhesion so, (as far as I understand things), you cannot
easily generate designs on the metal by this technique. However, as we see
from St Margaret's, you can then apply size and then gold or platinum leaf
to the stove enamelled surface to provide necessary dial furniture. 

Hmmm, I suppose that it might be possible to use masks and layers of
different colours and multiple firings to achieve a desired design because
my muguards had a grey undercoat as well as a later fired black top coat
and they didn't merge!. Might be worth considering when big dials are
involved - after all the St Margaret's dials are still going strong after
25 years - not bad for any dial finish.

Patrick

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Re: strange longitude

[JOHN DAVIS]

Dear Frank et al,
   
  I note that the letters 'PI' (as well as PII and PW) appear as one of the 
centres of Oughtred's Horizontal Instrument.  They are actually engraved on the 
instrument made by Elias Allen.
  Perhaps this is another red herring.
   
  Regards,
   
  John D
  ---

Frans W. Maes [EMAIL PROTECTED] wrote:
  Dear Frank  all,

On the meaning of PI Long:
Waugh uses the symbol P in his computational treatment of the declining 
dial on p. 80. The P values for each hour line in table 10.2 are what 
Holwell (in Clavis Horologiae, London 1712) calls the polar angles. The 
polar angle for noon equals the so-called difference in longitude DL. 
Converted to time, this is the time of the sub-style line. So here is at 
least a link between P and Long.
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Re: Irish Maker

[JOHN DAVIS]

Hi Tony,
   
  From the forthcoming Second Edition of Jill Wilson's Biographical Index of 
British Sundial Makers from the Seventh Century to 1920 we have:
  SEWARD John  A Dublin mathematical instrument maker, known to have made ring 
dials.
  Apprenticed to Gabriel Stokes in 1715, John Seward was working on his own 
account at least to 1740 and perhaps 1750. A mechanical universal equinoctial 
dial is in the National Museum of Dublin (No. 578-1910) and another has been 
listed in a sale catalogue. A ring dial is also understood to be in a private 
collection.
  Sources:
  i)  Clifton, p.248.
  ii)  V  M, pp. 4, 134.
   
  ++
   
  Does this sound like your man? I can look up the Sources if you haven't got 
them.  
   
  Jill and I would be grateful for details to add to the database, please.
   
  Regards,
   
  John Davis
  ---

Tony Moss [EMAIL PROTECTED] wrote:
  Fellow shadow Watchers,
I've been asked to reproduce an 
Irish dial but the florid engraving has deteriorated in places. It may 
possibly be 'Seaward DUBLIN 1750'. 

Can anyone throw light on this please/

Tony Moss
Lindisfarne Sundials.
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Re: An unusual Polyhedron

[JOHN DAVIS]

Hi Frank,
   
  Thanks for your kind comments on the Bulletin cover.
   
  I think you are a little harsh on the Downing Site polyhedral dial: I don't 
know of many dials with a gnomon pierced with the outline of a camel (alluding 
to eye's of needles, perhaps?!) or which shows so well that the gnomons of 
dials on any plane are all parallel.
   
  I hadn't noticed that the polyhedron isn't one of the common ones used for 
dials. I wonder if there was a dialling reason for choosing it or whether it 
was just an in-joke reflecting the work of Cambridge mathematicians at the time.
   
  Regards,
   
  John D
-
Frank King [EMAIL PROTECTED] wrote:
  Dear John
CAMBRIDGE POLYHEDRAL DIAL

I have just received the June BSS Bulletin...

You are to be congratulated on the cover photograph.
Somehow, you have contrived to make what I regard as
one of the most unprepossessing dials in Britain seem
almost elegant!

For over 40 years my normal place of work has been
approximately half way between this dial and the Queens'
Dial and there could hardly be a more contrasting pair!

There is a curiosity about the polyhedron itself. Until
about 18 months ago I thought this was a straightforward
small rhombicuboctahedron, an Archimedean solid. This
incorporates three mutually perpendicular bands of eight
squares with the gaps filled with triangles.

Amongst other properties, three squares and one triangle
meet at each vertex. This is very clear in your photograph
as is the horizontal band of eight squares.

Rather late in the day, it suddenly dawned on me that this
is NOT a small rhombicuboctahedron. Have a look at your
photograph. You will see that there are NO vertical bands
of eight squares.

This is a pseudorhombicuboctahedron which is NOT an Archimedean
solid because it doesn't have octahedral symmetry. It won't
morph into itself when rotated about a horizontal axis. See:

http://en.wikipedia.org/wiki/Pseudorhombicuboctahedron

You correctly note that Sir William Ridgeway and his wife
Lucy were the donors of the dial. They had a daughter, also
called Lucy, who married John Archibald Venn who was at some
time President of Queens' College. I wonder which dial he
preferred!!

John Archibald Venn's father was the better known John Venn
whose name is forever linked with the well-known diagram.

Best wishes

Frank




Dr J Davis
Flowton Dials---
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