Re: When the Transit of Venus Transits the Meridian...

tell me I'm wrong! Frank King Cambridge University England -

Re: When the Transit of Venus Transits the Meridian...

Hi Gianni, Thank you for your illuminating calculations. I have now reproduced your figures. As always, I find your explanations both fascinating and challenging! At noon on 8 June I think the altitude of the sun will be about 67.4 degrees in Milan. If the hole height is 23821mm then the

Re: Wall Declination Measurement

Dear Alex, Thank you for your rapid reply... As architect my comment on no.1. is that the north arrow which we place in drawings (at least the ones I place) are based on the North direction on large scale survey maps supplied by planning authorities and on which the drawing would be based.

[no subject]

of date. Not that we live long enough to notice! Happy Christmas Frank King Cambridge, U.K. -

Re: Oblate Spheroid correction for computing distances?

of the horizon is perpendicular to the local gravitational vector. This means you can use a normal sextant or other instrument that measures relative to the horizon or you can use an instrument that has some kind of spirit-level built in. Beware of massive mountains nearby! Frank King University

Re: Birthday

version) where, by the way, there are many interesting sundials. Never mind. I like to be reminded of this revolutionary! He is a hero of mine. Frank King University of Cambridge England -

Re: Magnetic variation.

a magnetic compass will ever give you. Richard Langley has already explained why. He is right! If you want really good results with the GPS then you need to use very expensive kit that uses a master-slave system but that won't be necessary if you just want to be within a degree or so. Frank King

Re: calendar

and a different culture. You many need to read all that three times to take it in but I am pretty sure it is true! Frank King University of Cambridge England -

Re: sundials in Rome (Capitel of Italy)

very much. Frank King Cambridge University England. -

Re: explain analemmatic (human) sundial to children

'. Frank King Cambridge University England. -

Another human sundial for children

sundial this is. It is a SPEAKING SUNDIAL and it is the only one in the whole world.' Frank King Cambridge University England -

Re: Declination approximation?

Dear John Is there an approximate formula for the declination of the sun vs day number? This is a tantalising story which doesn't really have a happy ending! Only gluttons for punishment should read any further... Your solution is a good starting point: I just tried the obvious

Re: Declination approximation?

Dear John, ... by now, you will have received a copy of the scanned and OCRed paper which was the first publication of this equation. That's fascinating. Many thanks. It's always good to see the original paper and this seems not to be acknowledged in the BSS Glossary under `Sources'. I

Re: Roman Numerals - as a test message

are often not equal because one can deliberately choose to place the noon line off-centre and so so on but it would be interesting to know whether your data support the naive hypothesis! Frank King Cambridge University England -

Re: Wall Declination Measurement

can easily come to grief. For large wall dials, a good deal of practical dialling amounts to a hard slog analysing survey data and undertaking laborious error analysis, but that's another story. Frank King Cambridge, U.K. -

Re: Turtle Bay Sundial Bridge opens

the original hole. You have to use the outer envelope. Unless a nodus designer understands all this, it is ever so easy for the anti-shadow from the hole to exceed the size of the shadow of the surrounding disc. The result is indeed pretty useless! Frank King Cambridge University England -

Re: Dawn shadows on an east/west wall

is denying us. All we need now is a client for Tony Moss who wants a wall dial in the Antarctic and we can see this at work. Frank King Cambridge University England -

East/West walls and the North/South divide

it is below, than the poor people in Australia! Frank King [In Cambridge where it is raining heavily and all thoughts of sundials are purely theoretical at the moment :-(( ] -

New Zealand Puzzle

and azimuth. Suggestions welcome! Frank King Cambridge, U.K. -

Re: Horizontal equivalence

equipped with solid-state gyros for levelling purposes! Frank King Cambridge, UK -

Re: Author of poem

. I couldn't persuade my clients (a Joint Committee of the House of Commons and House of Lords) to use proper Shakespeare. Gh! Frank King Cambridge, U.K. -

Re: On the greatest size of an analemmatic and more

the tiles on an outside dial. I am feeling a serious lack of experience! Can anyone help? Frank King Cambridge, U.K. -

Re: Is the USA 'Daylight-Saving' period to be extended ?

for this eccentricity! Frank King Unrepentant Sinner Cambridge, U.K. -

Re: Is the USA 'Daylight-Saving' period to be extended ?

will accept that this is largely a matter of taste. Frank King Cambridge, U.K. -

Re: Which longitude/latitude to use?

this. Frank King Cambridge, U.K. -

Re: Reading at a Distance

many of these tricks! Frank King Cambridge, U.K. -

Re: Meridiana of Milan

and are quite technical but are not really fit for general consumption. Frank King Cambridge, U.K. -

Save the Leap Second

news. Quite apart from anything else, having a leap hour some time in the future seems like building up a problem that will make the Y2K nonsense seem a trivium. What do others think? Should we take to the streets? Frank King Cambridge, U.K. -

Re: Save the Leap Second

Dear Fer, Does another correction for sundials, as Jean Meeus writes, also means an extra shift in the system wintertime/summertime?. I suppose that will be up to individual Governments or, in our case, some group in Brussels but it seems almost inevitable. A cumulative drift of up to an

Re: Save_the_Leap_Second

Dear Wolfgang, You ask: Who cares about UTC in every-day life? Well all diallists and anyone who uses astronomical tables care about UTC precisely because it is, currently, guaranteed the same as UT1 to within 0.9s and we can ignore that difference. When UTC-UT1 is even a few seconds, never

Re: WSJ.com - Why the U.S. Wants To End the Link Between Time and Sun (fwd)

Dear Fred, Thank you for this snippet about the Leap Second... Copy and paste the following into your Web browser to access the sent link: http://www.emailthis.clickability.com/et/emailThis?clickMap=viewThisetMailToID=1114314915pt=Y I am impressed that the Wall Street Journal should take

Re: The J. Carmichael stone technique...

Dear All, I was fascinated to read... John Carmichael's Stone Cutting Carving Technique This eloquently describes an interesting set of procedures. What is particularly noteworthy to me is that there is almost no overlap with standard stone cutting procedures that I have come across in

Re: The J. Carmichael stone technique...

Dear Andrew and Jack, Your observations definitely resonate with me, especially the comment that... ... a relatively inexperienced stone cutter can use John's technique and produce something that is at least acceptable without years of practice. I have been incredibly lucky to have worked

Re: Many a slip....

that experience again! It is not quite so easy to change XI to IX though perhaps you could ink in a little minus sign to give X-I. Just an idea :-) Frank King -

Re: east and west, an afterthought

Dear Chris I would argue that the rhumb line is itself virtually obsolete. I readily accept your line of thought, but a rhumb line legacy is still very much with us. I refer, of course, to Mercator's Projection where all straight lines are projections of Rhumb Lines. Mercator's is probably

Re: Firenze clock

Dear Willy, It is hard to find definitive information about clocks which show Italian hours. A number survive in Italy mostly in the Rome area. What I write now should not be taken as wholly reliable! Napoleon wanted French time everywhere of course and most Italian hours clocks were changed

Re: Holbein's `The Ambassadors'

Dear All, Nicola Severino's article on the Holbein painting, The Ambassadors, is most interesting and adds to the corpus of understanding of this fascinating picture. For those who read English but not Italian, there are many references to The Ambassadors, including BSS articles which Nicola

Seeing in 2006

Dear All, How should a diallist see in 2006? After all, the new year starts at midnight when there is no sun (except in the Antarctic) and, this time, it is new moon too so those who like moon dials (always a disappointment in my experience) will also be out of luck. Well, we do have a Leap

Rods versus Knife-Edges

of the edge. This is error prone and, to some extent, subjective. I say `spare the rod and spoil the sundial'. Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Bitter at Twisted

, use a nocturnal! Frank King --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Nodi Shadow Experiment

it to be but further into the geometric shadow. You get a false reading. For all their faults, spheres and discs and holes are better bets because you can estimate the centres of their shadows (or spot of light) better. Frank King Cambridge, U.K

Re: Sundial Motif to Be Featured on New Canadian $10 Coin

://users.eastlink.ca/~srgl/louisbur.htm There are many ways a sundial can make a botch but this isn't one of them! Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: McDonald's billboard (A sundial?)

) constant. We should be grateful to the McDonald's Ad Agency for pointing the way to some potentially useful theory! The only snag is that anyone who exploits this idea may fall foul of some U.S. patenting law! Frank King Cambridge, U.K. --- https

Re: Expanded Nodi Shadow Experiment

Dear John, That is a splendid experiment...  http://advanceassociates.com/WallDial/NodusShadowExperiment.pdf It illustrates all kinds of interesting aspects of nodus design The Purpose, Setup and Execution all earn top marks. The Conclusion, though, is subject to a little caveat... Let's

Re: Expanded Nodi Shadow Experiment

Dear John (and Edley), Your experiment continues to fascinate me and I have some fresh comments which include an experiment that everyone can carry our very easily and which amplify Edley's remarks. First, many thanks for your dimensions: the cardboard thickness: 3/32 the hole diameter: 1/4

Re: Expanded Nodi Shadow Experiment

Dear Mac, Thank you for sharing Bill's sketch with the list. I really appreciate his phrase... I'm a bug on symmetry... I think that pretty much describes me too! Moreover, his design satisfies the symmetry goal well. In particular, the fat rod extends beyond the crossing which keeps me

Re: Expanded Nodi Shadow Experiment

Hi Gianni, It is always good to hear from you on this list. Most of what I know about nodus design is a result of reading your papers so your message is of very great interest. You made this comment... I think that it is advisable that the plane of the hole is a  polar plane with the hole

Re: Expanded Nodi Shadow Experiment

Hi Gianni, Thank you for your splendid response... I hope that our Emails, interesting for us, don't bore other readers :-) I promise this one will be short!! Oh, and your image arrived first time (a little corrupted but I could read it). This time I agree with EVERYTHING in your reply.

Re: RE Dials - ore francesi

and French Hours (and just a hint about what makes them French!) in my frivolous spoof in: http://www.cl.cam.ac.uk/users/fhk1/Maggiore.pdf Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Message from Giovanni Bellina

pictures that are new to me. There is also a dialling schema (you key in parameters and it does the calculations). Yes, this site might interest a few... http://www.astrohk.cz/slunecni_hodiny.html Frank King Cambridge, U.K. --- https

Re: Dials

area. Unfortunately, there seem to be only two people in the world who are interested in Italian-hours clocks! I am one and Nicola is the other! I hope I am wrong!! Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Dials

Dear Gianni, I am most interested in your comments and those of Roger Bailey and Nicola Severino... ... in my opinion, the Italian-hours clocks have never existed This is a big disappointment to me :-) I ... asked a question that now I repeat: What are the differences from a mechanical

Re: Equal hours?

Dear Mac, Fer de Vries has answered your question but he could be misinterpreted... Of course you are right that an Italian hour and a Suntime hour aren't of the same length each day. But we are talking about 30/24 second of time per hour as maximum... This is true if you take 24 hours as

Re: sundial on a cylindrical wall

wall has a best-fit vertical plane! It is just that the ortho-style distance varies rather a lot from the mean! What I am interested to know, is: 1. `How close to a true cylinder is your wall?' 2. `How did you allow for the inevitable undulations? All the best Frank King Cambridge, U.K

Re: sundial on a cylindrical wall

Dear Mac Many thanks for your message... Would you be willing to expand on the eight steps you listed in your procedure for dealing with a supposedly flat wall? Yes, I am willing but this is a bit of a risk! Each step could be a whole chapter of a book! I don't think the list would be too

Re: AW: Summaries of bulletin - Block dials

Dear Ruud, I very much agree with your comment... Mathematically, a polyhedron ... need not be regular or indeed convex. My favourite polyhedron is the Szilassi Torus. This is not just concave but, as the name implies, it is equivalent to a ring. This polyhedron has just SEVEN faces. Each

Re: Varying amounts of sundial correction

Zealand which is the nearest land mass of any size. Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Europes largest horizontal sundial

Have a look at Europe?'s largest horizontal sundial... How large is largest? No dimensions are given :-( There is a large sundial in Britzer Garten in Berlin for example and a huge compass rose dial in Lisbon. I don't have the dimensions of any of the three but they are all very big!! Frank

GPS and Azimuth

. This is serious professional stuff costing between $50k and $100k. Specialist contractors who use this kit all the time are available for hire. I have used three different such contractors for big (and expensive!) sundials over the past 10 years. Frank King Cambridge, U.K

Re: Australian Sun

? At least Italian Hours are safe!! Frank King --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: strange longitude

the declination of the dial which gives it some relevance. Maybe this is stretching the idea of a Position Line too far!! Frank King Cambridge U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: strange longitude

that by 1845 the idea was well known to navigators and others. Writing PL on your sundial might be a way of showing that you were using modern ideas! OK. I'm clutching at straws! Incidentally, this quoted figure for longitude is within a few arc-minutes of being the co-latitude. Weird! Frank

Re: Porcelain Sundials

Dear John, Thank you for your message. I was delighted to have the opportunity to meet you face to face at the BSS conference and to hear about the techniques you use... especially our discussions about the possibility of using durable fired porcelain instead of paint I shall certainly

Re: strange longitude

Dear Gianni, You are truly wonderful! You have, come sempre, solved the problem! We have all these people on the English list wondering about PL and we have to wait for you to interpret our English! I didn't think of the Geocentric Latitude and I certainly didn't think of the Reduced Polar

Re: Porcelain Sundials

Dear John, Does anybody know if the four round blue dials on the tower at Westminster Abbey in London are made of porcelain (vitreous enamel)? They are on the Tower of the Church of S. Margaret's Westminster (quite different from Westminster Abbey) and are by Christopher Daniel. You can see

Re: strange longitude

at that boys, the schoolmaster would say, It is now 12 noon everywhere along the Pl longitude. This has been the best thread for a long time!! Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: R: Re: A very interesting dial

Dear Gianni, Mea culpa! You are of course right. The summer solstice arc indeed curves upwards on a cylindrical surface. I was assuming that the surface was made of flat segments (as in the external photograph) but this is not so. - The higher line (at ¾ of the height of the doors)

Re: mottos or mottoes - general questions

. This Latin is certainly seen on sundials! Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Plaster Wall Sundials?

a photograph taken at a much less convincing time just so we can all be sure we are not suffering from a double bluff! Maybe even the gnomon and its shadow are painted too!!! Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman

Re: Southern/Northern exposure

they are made from a matt material, you can get blinding reflections from them when you try to read the time near noon!! Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

An unusual Polyhedron

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

Re: simultaneous sunset

as being 2 deg 23'. This gives the solar declination as -18.7 degrees. I expect I have goofed. Some bright youngster can now tidy up my efforts!!! Best wishes Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: simultaneous sunset

Dear Frank et al, An intriguing side issue to your puzzle is that it relates to the discussion about the Hawkeshead dial and the notion of a Plane's Longitude and, implicitly, the notion of a Plane's Latitude. Once you have taken on board these notions, the simplest way of expressing the

Re: simultaneous sunset

Dear Frank et al, After a second night sleeping on your nice puzzle I realised that I DID make a small goof in one of my assertions and no one has picked me up on it!! In the formula: tan(dec) = [-]sin(d)/sqrt(t1^2 - 2.t1.t2.cos(d) + t2^2) I asserted (correctly) that the argument of the square

Re: An unusual Polyhedron

Dear John, Thank you for your suggestions about repairing or restoring the Downing Site sundial... ... a possible solution might be to make a set of brass dialplates, each a little smaller than the polyhedron's faces, and apply them to the existing stone around the gnomons.  These would

Re: simultaneous sunset

Dear Warren, Happy Summer Solstice! You ask an astute question: Are you saying below that ANY two locations MUST have a moment of mutual sunrise/sunset? Well, I am ALMOST saying that and the mathematics IS saying that... The declination of the sun is, of course, constrained to be between

Re: Help Oscar!

when I use a 300W lamp and I can wander around simulating a winter day or a summer day and so on. A 300W lamp is a bit dangerous for children but, on a small scale, a suitable torch would do. Enough! Frank King Cambridge, U.K. --- https://lists.uni

Re: Help Oscar!

Dear Roger, I enjoyed your response to my playground thoughts and I enjoyed your puzzle even more... Calculate the time for the sun to be at azimuth of 45º for the summer and winter solstices for a given latitude, say 50º. Alas, I can add nothing to Fred Sawyer's reply. It is easy to

Re: Solar Qiblah

Dear Roger and Mashallah, Many thanks to you both for a most interesting dialogue. May I suggest three sundialling heroes who, you will see, are very relevant your discussion: 1. Frank Evans - The Inspirer 2. Gianni Ferrari - who pointed us at... 3. John Good - who can laugh at us

Re: Seasonal markers for Analemmatic Sundials

Dear Roger, No one seems to have responded to your interesting letter to the Editor of the BSS Bulletin. May I join in? SEASONAL MARKERS You write about Seasonal Markers on analemmatic sundials. Seasonal Markers are two special points on the major axis of the ellipse (of hour marks). If you

Re: Seasonal markers for Analemmatic Sundials

in the Lambert circles!] Perhaps you should go out with spray paint one night and mark in some Lambert circles on an analemmatic sundial near you!!! Best wishes Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: God's Longitude and the Lost Colony of Virginia

fraction of a day the year exceeds 365 days! What we can be sure of is that for the period 500 years either side of where we are now, this fraction averages a lot closer to 8/33 days (the Omar Khayyam value) than it does to 97/400 days (Pope Gregory's value). I would like to thank Frank King

Re: Sundials in Hong Kong?

Dear Doug, Hong Kong is one of my favourite places but I do not recall any sundials alas. That said, there is one place which is just asking to have a sundial of a rather special kind and you simply must visit it... This is the extraordinary HSBC Headquarters Building which, in plan, is a

Re: The 'hazards' of sundialling. Phew!

Dear Tony, Sundialling is undoubtedly a very dubious activity whose practitioners should be treated with the greatest suspicion. Try going round a London Square with an architect's drawing full of arrows all pointing at the Stock Exchange and labelled clear view 11:30 to 2 or in shadow after 3pm

Re: Minimalist sundial

additional assumptions you have to make. Hey, I feel an examination question coming on! Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Margaret Stanier Memorial Meeting

not sure about dialling. Like many Cambridge Colleges, Newnham has a couple of sundials: a late 19th century horizontal dial and an early 20th century pillar dial with four dial faces). The College has limited parking alas. Frank King Cambridge, U.K

Re: Winter Solstice at Newgrange, Ireland

that this value changes over the centuries. Is there a straightforward formula that gives the azimuth of sunrise at the solstice as a function of one's latitude?  Yes, see above, but don't trust it! Using someone else's formula is rather like using someone else's toothbrush. Best wishes Frank King

Re: Winter Solstice at Newgrange, Ireland

aren't wishing you had never asked the question!!! Best wishes Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Winter Solstice - slight correction

the time so again there is no sunrise and therefore no meaningful azumuth. You get analogous problems in the antarctic when phi -67 degrees. Best wishes Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: Winter Solstice at Newgrange, Ireland

Dear Warren, Many thanks for supplying Bill Gottesman's comments which I very much take to heart. Getting good sightings at sunrise and sunset in real life is seriously challenging and even when you are in luck, the shadows are weak and the effect of refraction is at its greatest and you have to

Re: Winter Solstice at Newgrange, Ireland

Dear Geoff, Yes, you are absolutely right. Silly me for not spotting a trivial simplification! It is, indeed, much neater to write: cos(az)=sin(dec)/cos(lat) This also readily shows that reversing the sign of the declination results in 180 degrees being added to (or subtracted from)

Dialling Puzzle for Christmas Eve

but, on thinking about it, I can see several ways to arrange for shadows to begin lengthening at exactly 3 o'clock. Would anyone else like to make some suggestions? As it happens, with just over an hour to go, it is 100% overcast here so this puzzle is rather academic! Happy Christmas Frank King

Re: Dialling Puzzle for Christmas Eve

Dear Geoff, Yes, I agree with your hasty calculation (having taken far longer than you to do it!)... A hasty ... calculation suggests that a vertical dial declining about 38 degs west of south in the latitude of Cambridge might experience its shortest shadow around 1500hrs. This was one of

Re: Azimuth of Sunrise - Sunset

Dear Jack, I enjoyed your the motivation... My original question was sparked by wondering about the maximum deviation from east-west at the solstice(s) so I could display my erudition and bore people with comments like: The sun rises in the East and sets in the West, right? Well, not

Re: Azimuth of Sunrise - Sunset Proof

Dear Roger, You chide us :-) ... few have been doing their homework, proving that Cos Phi = Sin Lat / Cos Dec The truth is that Geoff Thurston supplied the answer (well almost the answer) on Christmas Eve so I thought we could all have a rest! Geoff and you have both referred to the same

Re: Urban Meridian

of the buildings in the vicinity? What worries me is that this splendid device will be rather wasted in a location with so much light pollution. Maybe the light problem is not as bad as I am guessing? Best of luck Frank King Cambridge, U.K. --- https

Re: New York Times

parts of Scotland. You will need to search in a very big dictionary to find out more! Best wishes Frank King Cambridge, U.K. --- https://lists.uni-koeln.de/mailman/listinfo/sundial

Re: New York Times

Dear Willy, Following your suggestion I was searching in a very big dictionary to find out more... Alas, your dictionary was not quite big enough! The full Oxford English Dictionary will give you details of the meaning of quaint as understood by Shakespeare and Chaucer. Interestingly it is

Re: Cute ad-hoc dial at AutoDesk Labs

an eye on this shadow you can get a rough estimate of the time of transit and you can even more readily estimate how much daylight you have left before you need to return to your cave! We can be confident that primitive homo sapiens made considerable use of this kind of sundial! Best wishes Frank

Re: Sundial for odd time zone

Dear John, Your question intrigues me... The sundial will be located at local meridian (longitude) -77.0769 degrees.  If it had a normal time zone, the Standard Meridian would be -75 degrees (UT+ 5 hrs.). True. But since its Time Zone is UT +5:30, then wouldn't its Standard Meridian be

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