Re: Ceiling Sundial Limitations
Hi Anselmo, Fer, Ceiling Dialists, This is a repeat of a message I sent earlier that bounced. My ISP sends my mail with one of three addresses depending on which site I'm logged into, so I changed my sundial address to this one: [EMAIL PROTECTED] Sorry if you receive more than one copy of this. It seems that one solution to a ceiling sundial, within the tropics, would be to make a mesh room, with mesh ceiling and walls, Enough sun could come through to strike the mirror and project a spot which could be seen on the mesh surface. colored twists of wire could be hung to mark these. Perhaps the mirror could be made somewhat larger with an X marked from corner to corner, thus allowing us to find the center of the light spot even if partly blocked. Since we, ourselves might create this room, the surface of the ceiling could be quite level, perhaps using the hose with water in it technique or a laser level. As a note: Perhaps false ceilings were invented to give us a flat ceiling for dials when the old ceiling was tilted or lumpy. g Or, as you suggest, we could mount different mirrors in multiple windows or at multiple tiltings, coloring them different colors by a dip in colored lacquer and marking their spots with colored paint or thumbtacks. It would surely be a colorful way to tell time. :-) Couldn't one mount a playhouse in a window and construct a ceiling dial on it's small ceiling? What a deal for miniaturists! ( It could solve the flatness problem ) Yes, Fer's analysis is really splendid!! Edley Anselmo wrote: Wow! The analysis of the limitations of polar ceiling sundials made by Fer de Vries is just splendid. Essentialy the problem is: if we move the mirror inwards it could fall under the ceiling shadow and thus produce no dot of light, and if we move it outwards the ray of light goes back outside when the Sun is high, so, once again, we are in one of these equilibrium-of-forces problem. In my opinion the worst limitation is the one imposed by the size of the window, and I guess there are no general solutions and we are bound to a trial-and-error balance analysis for each case. Maybe we could have several non-overlapping mirrors, each one for every case, but then our problem looses a lot of its simplicity. Anselmo Pérez Serrada Dialists, In my mind I wanted to make a try for a polar ceiling dial at latitude 52 degrees, mid Netherlands. In the attached picture you see the mirror M at a distance g from the ceiling. The polar pattern for this configuration is drawn below left and I want to have the hours 8 am - 4 pm on the dial, if possible. ( no longitude correction in this story ) The line BC then is about the limit of the space I need on the ceiling, or with other words, the mirror should be inward the room over a distance AB. Let's now have a look if the sun will shine on the mirror all year at noon. It's obvious that I need to look for the limits at summer solstice. It is seen that during the summer solstice the sun can't shine on the mirror at all. The first change I need to make is to cut of the ceiling at the line PCQ in which C is the intersection point of the summer ray and the ceilng. In the hourline pattern the hours before 10 am and after 2 pm will be cut of too and the first conclusion is that at summer solstice the dial is useable from about 10 am to 2 pm. However, there are more things to concider. In this configuration the mirror will catch the sun at summer solstice only at noon. Shortly before and after noon the mirror is in the shade. To see this we need to imagine a vertical south facing dial through AM with a (pin)gnomon of length AC. That pattern is drawn below at the right side. At noon the edge of the ceiling gives a line of shadow KL and the mirror just catches the sun. Before noon and after noon this line of shadow moves down ( to the right in the drawing ) and the mirror won't catch the sun. It sounds strange, after noon the altitude of the sun decreases and also the shadow on a south facing dial decreases. Yes, this is true and can be seen with the shape of the dateline for the summer solstice. Before and after noon this date line in going down. So at the summer solstice my dial only gives a flash at noon and no more... The third problem to concider is the width of the window. Because the mirror is inside the room the azimut of the lines from mirror through the edges of the window also will give limitations For this an analemmatic dial or Oughtred dial could be of use to see what the limitations are. Who will show us the first real polar-mirror-ceiling dial? Who has an inclined ceiling, higher at the south end? Won't that be better? Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E
Re: Ceiling Sundial Limitations
Dialing friends
The idea of
mesh roofs and {Snip:} different mirrors in
multiple windows at multiple tiltings, coloring them
different colors by a dip in colored lacquer and
marking their spots with colored thumbtacks
This reminds me of a comment my wife made to me after
I had stayed up a good part of the night working on my
dail, At some point it becomes a folly.
I spent the next 2 nights doing the same thing.
Still looking for folly,
Mike
36.9151 : 121.3539
--- Edley McKnight [EMAIL PROTECTED] wrote:
Hi Anselmo, Fer, Ceiling Dialists,
This is a repeat of a message I sent earlier that
bounced. My ISP sends my mail with one of three
addresses depending on which site I'm logged into,
so I changed my sundial address to this one:
[EMAIL PROTECTED] Sorry if you receive more than
one copy of this.
It seems that one solution to a ceiling sundial,
within the tropics, would
be to make a mesh room, with mesh ceiling and walls,
Enough sun could
come through to strike the mirror and project a spot
which could be seen
on the mesh surface. colored twists of wire could
be hung to mark these.
Perhaps the mirror could be made somewhat larger
with an X marked from
corner to corner, thus allowing us to find the
center of the light spot
even if partly blocked. Since we, ourselves might
create this room, the
surface of the ceiling could be quite level, perhaps
using the hose with
water in it technique or a laser level.
As a note: Perhaps false ceilings were invented to
give us a flat
ceiling for dials when the old ceiling was tilted or
lumpy. g
Or, as you suggest, we could mount different mirrors
in multiple
windows or at multiple tiltings, coloring them
different colors by a dip
in colored lacquer and marking their spots with
colored paint or
thumbtacks. It would surely be a colorful way to
tell time. :-)
Couldn't one mount a playhouse in a window and
construct a ceiling dial on it's small ceiling?
What a deal for miniaturists! ( It could solve the
flatness problem )
Yes, Fer's analysis is really splendid!!
Edley
Anselmo wrote:
Wow!
The analysis of the limitations of polar
ceiling sundials made by
Fer
de Vries is just splendid. Essentialy the problem
is: if we move the
mirror inwards it could fall under the ceiling
shadow and thus produce
no dot of light, and if we move it outwards the
ray of light goes back
outside when the Sun is high, so, once again, we
are in one of these
equilibrium-of-forces problem. In my opinion the
worst limitation is the
one imposed by the size of the window, and I guess
there are no general
solutions and we are bound to a trial-and-error
balance analysis for
each case.
Maybe we could have several non-overlapping
mirrors, each one for every
case, but then our problem looses a lot of its
simplicity.
Anselmo PÈrez Serrada
Dialists,
In my mind I wanted to make a try for a polar
ceiling dial at latitude
52 degrees, mid Netherlands.
In the attached picture you see the mirror M at
a distance g from the
ceiling. The polar pattern for this
configuration is drawn below left
and I want to have the hours 8 am - 4 pm on the
dial, if possible. (
no longitude correction
in
this story )
The line BC then is about the limit of the space
I need on the
ceiling, or with other words, the mirror should
be inward the room
over a distance AB.
Let's now have a look if the sun will shine on
the mirror all year at
noon.
It's obvious that I need to look for the limits
at summer solstice.
It is seen that during the summer solstice the
sun can't shine on the
mirror
at all.
The first change I need to make is to cut of the
ceiling at the line
PCQ
in
which C is the intersection point of the summer
ray and the ceilng.
In the hourline pattern the hours before 10 am
and after 2 pm will be
cut
of
too and the first conclusion is that at summer
solstice the dial is
useable
from about 10 am to 2 pm.
However, there are more things to concider.
In this configuration the mirror will catch the
sun at summer solstice
only
at noon.
Shortly before and after noon the mirror is in
the shade.
To see this we need to imagine a vertical south
facing dial through AM
with
a (pin)gnomon of length AC.
That pattern is drawn below at the right side.
At noon the edge of the ceiling gives a line of
shadow KL and the
mirror just catches the sun. Before noon and
after noon this line of
shadow moves down ( to the right
in
the drawing ) and the mirror won't catch the
sun.
It sounds strange, after noon the altitude of
the sun decreases and
also
the
shadow on a south facing dial decreases.
Yes, this is true and can be seen with the shape
of the dateline for
the summer solstice. Before and after noon this
date line
RE: Ceiling Sundial
Dear all To Judge by Judith's reply I clearly spoke out of turn (albeit from that road that leds to hell!). My apologies for any offence given. Regards Andrew At 13:20 4/1/02 -0500, Romano, Judith wrote: Dear Sundialists: Thank you again for your notes of assistance and comments. This e-mail group is very useful, with responses that are both attentive and thorough. I will try to keep my note brief. With a great south facing house, the mirror placed half-way up the window, and limiting the hours from 9am to 3pm, fortunately only the 3pm sun dot was appearing on the opposite wall. The markings for the remaining three times in which sun time and watch time closest agree (Apr 15, Jun 14, and Sep 2), will be shorter and allow me to make lines using three other reference points. My children have enjoyed the process so far -- watching the spot go across the ceiling, and seeing mathematics and science in action! Narrow straight molding (painted white to match the ceiling) placed on these lines (the entire width of the ceiling) to depict the hour lines, will make this dial discreetly decorative, yet functional. With the large amount of interest and enthusiasm generated by this topic, I'll have to take some photos during it's creation, and once completed, share them with the sundial group to demonstrate the whole process and it's success. Judith FYI... For those interested in HUMAN/GARDEN SUNDIALS as well (last summer's project with my children), I've created a fill-in worksheet that computes the calculations automatically in inches with longitude correction (for Northern Latitudes and Western Longitudes) -- one just needs to know their latitude (and optional longitude and time zone for correction), and the desired size. I've been working with John Hoy to have it posted at his website (http://www.cyberspace.org/~jh/dial/). I will be casting these sundials onto the area schoolyard blacktops in March (before Daylight Savings in April). I believe this community service project should be made available to all -- free of charge! -Original Message- From: Steve Lelievre [mailto:[EMAIL PROTECTED] Sent: Friday, January 04, 2002 9:58 AM To: sundial@rrz.uni-koeln.de Subject: Re: Ceiling Sundial I agree, John. At one solstice the EoT is about +2 minutes, and at the other it is about -2 minutes so there would be only a slight discrepancy. Too small to worry about, especially as this is a junior school project and Judith is trying to avoid too much complicated explanation. I like her approach for its simplicity, but there's one potential problem which I don't know how to solve. What happens if the summer dot is on the ceiling and the winter dot is on a wall? How do you draw the straight line connection? I can imagine the method being used by other teachers in the future, and people forgetting to take back Daylight Saving Time for the summer labels, or vice versa. Steve As it turned out (in my opinion), her original idea was correct. John I have the tiny lipstick mirror mounted at my window frame (half way up) , and was told that the easiest way (void of all the mathematical calculations that they would not understand) is to mark each hour in the day during the winter and summer solstices (12/21 and 06/21) -- then connect the dots. Granted this process takes six months to complete, but it would ensure that all longitude corrections are incorporated, effortlessly. --Andrew Pettit e-mail: [EMAIL PROTECTED] Postman Pat: 3, Lucastes Road, HAYWARDS HEATH, West Sussex, RH16 1JJ, ENGLAND Tel. UK: (+44) (0)1444 453111
Re: Ceiling Sundial
minutes are equal to the diameter of the reflected sunspot on your ceiling. At 10:57 4-1-2002 -0400, Steve Lelievre wrote: At one solstice the EoT is about +2 minutes, and at the other it is about -2 minutes so there would be only a slight discrepancy. Too small to worry about, especially as this is a junior school project and Judith is trying to avoid too much complicated explanation. - Th. Taudin Chabot, home email: [EMAIL PROTECTED]
Re: Ceiling Sundial
I have seen much worthy comment on the above giving far more information than I could possibly imagine. However, and please do take this to be a constructive comment, Is it likely to have helped Judith in her quest If I have missed something then please forgive me. Regards Andrew Pettit At 10:04 20/12/01 -0500, Romano, Judith wrote: Hello Sundial Friends: I am planning on making a ceiling sundial (as a project with my children in an actual science/math application). I have the tiny lipstick mirror mounted at my window frame (half way up), and was told that the easiest way (void of all the mathematical calculations that they would not understand) is to mark each hour in the day during the winter and summer solstices (12/21 and 06/21) -- then connect the dots. Granted this process takes six months to complete, but it would ensure that all longitude corrections are incorporated, effortlessly. Any opinion or comments today, from anyone who has done one, would be quite helpful, (as this process is to start tomorrow)! Thanks! J Romano
Re: Ceiling Sundial
Hi Andrew As a former beginning dialist I know how Judith feels. While interesting to the List, all of the ideas about transparencies, lasers, an auxiliary dials probably just confused poor Judith. As it turned out (in my opinion), her original idea was correct. 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 - Original Message - From: Andrew Pettit [EMAIL PROTECTED] To: Romano, Judith [EMAIL PROTECTED]; sundial sundial@rrz.uni-koeln.de Sent: Friday, January 04, 2002 4:53 AM Subject: Re: Ceiling Sundial I have seen much worthy comment on the above giving far more information than I could possibly imagine. However, and please do take this to be a constructive comment, Is it likely to have helped Judith in her quest If I have missed something then please forgive me. Regards Andrew Pettit At 10:04 20/12/01 -0500, Romano, Judith wrote: Hello Sundial Friends: I am planning on making a ceiling sundial (as a project with my children in an actual science/math application). I have the tiny lipstick mirror mounted at my window frame (half way up), and was told that the easiest way (void of all the mathematical calculations that they would not understand) is to mark each hour in the day during the winter and summer solstices (12/21 and 06/21) -- then connect the dots. Granted this process takes six months to complete, but it would ensure that all longitude corrections are incorporated, effortlessly. Any opinion or comments today, from anyone who has done one, would be quite helpful, (as this process is to start tomorrow)! Thanks! J Romano
Re: Ceiling Sundial
I agree, John. At one solstice the EoT is about +2 minutes, and at the other it is about -2 minutes so there would be only a slight discrepancy. Too small to worry about, especially as this is a junior school project and Judith is trying to avoid too much complicated explanation. I like her approach for its simplicity, but there's one potential problem which I don't know how to solve. What happens if the summer dot is on the ceiling and the winter dot is on a wall? How do you draw the straight line connection? I can imagine the method being used by other teachers in the future, and people forgetting to take back Daylight Saving Time for the summer labels, or vice versa. Steve As it turned out (in my opinion), her original idea was correct. John I have the tiny lipstick mirror mounted at my window frame (half way up) , and was told that the easiest way (void of all the mathematical calculations that they would not understand) is to mark each hour in the day during the winter and summer solstices (12/21 and 06/21) -- then connect the dots. Granted this process takes six months to complete, but it would ensure that all longitude corrections are incorporated, effortlessly.
RE: Ceiling Sundial
Thank you everyone for all your e-mails. A lot of the e-mails were too technical for what I wanted to incorporate with my elementary-age children. However, the information was quite insightful and creative in it's own right, and worth a try in the future. I will basically be taking the hourly markings at the four times during the year in which clock time is as close to sun time as it will get (12/25 and 6/14 being the extreme points). That should do it! Thanks again to all! Judith -Original Message- From: John Carmichael [mailto:[EMAIL PROTECTED] Sent: Friday, January 04, 2002 9:31 AM To: Andrew Pettit Cc: sundial@rrz.uni-koeln.de Subject: Re: Ceiling Sundial Hi Andrew As a former beginning dialist I know how Judith feels. While interesting to the List, all of the ideas about transparencies, lasers, an auxiliary dials probably just confused poor Judith. As it turned out (in my opinion), her original idea was correct. 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 - Original Message - From: Andrew Pettit [EMAIL PROTECTED] To: Romano, Judith [EMAIL PROTECTED]; sundial sundial@rrz.uni-koeln.de Sent: Friday, January 04, 2002 4:53 AM Subject: Re: Ceiling Sundial I have seen much worthy comment on the above giving far more information than I could possibly imagine. However, and please do take this to be a constructive comment, Is it likely to have helped Judith in her quest If I have missed something then please forgive me. Regards Andrew Pettit At 10:04 20/12/01 -0500, Romano, Judith wrote: Hello Sundial Friends: I am planning on making a ceiling sundial (as a project with my children in an actual science/math application). I have the tiny lipstick mirror mounted at my window frame (half way up), and was told that the easiest way (void of all the mathematical calculations that they would not understand) is to mark each hour in the day during the winter and summer solstices (12/21 and 06/21) -- then connect the dots. Granted this process takes six months to complete, but it would ensure that all longitude corrections are incorporated, effortlessly. Any opinion or comments today, from anyone who has done one, would be quite helpful, (as this process is to start tomorrow)! Thanks! J Romano
Re: Ceiling Sundial
Andrew, The sundial list has served a dual purpose. The last note I got from Judith said that she was going to use the original method of marking the ceiling, using the new dates that I suggested. And, the discussion that followed seemed to be interesting to a lot of people on the list. Looks like win-win to me. ++ron
Re: Ceiling Sundial
On Fri, 4 Jan 2002, John Carmichael wrote:
As a former beginning dialist I know how Judith feels. While interesting to
the List, all of the ideas about transparencies, lasers, an auxiliary dials
probably just confused poor Judith.
As it turned out (in my opinion), her original idea was correct.
John
As others have said, this was a very good brainstorming discussion, with
multiple purposes. I also believe Judith's main objective - introducing
solar timekeeping to younger students - will be best served by the simple
and obvious technique of marking the hours at various times during the
year. It clearly indicates how the ancients kept time, building their
markers over long periods of time, perhaps generations. For those of us
with a bent towards nitpicking detail :{) the auxialiary methods discussed
introduced some possibly novel ways of solving a difficult layout problem,
and a good brain exercise.
The possible problem of a Winter hour point lying on the far wall, does
suggest it would be best to use more than two dates. If she were to
include the point in Spring where the EOT is zero, there should be two
points on the ceiling, at least. Extend the lines from the June points
through Spring, to where they intersect the ceiling/wall joint, then from
there to the Winter points. That should complete the mean-time line,
filling in the break.
Dave
37.29N 121.97W
RE: Ceiling Sundial
Dear Sundialists: Thank you again for your notes of assistance and comments. This e-mail group is very useful, with responses that are both attentive and thorough. I will try to keep my note brief. With a great south facing house, the mirror placed half-way up the window, and limiting the hours from 9am to 3pm, fortunately only the 3pm sun dot was appearing on the opposite wall. The markings for the remaining three times in which sun time and watch time closest agree (Apr 15, Jun 14, and Sep 2), will be shorter and allow me to make lines using three other reference points. My children have enjoyed the process so far -- watching the spot go across the ceiling, and seeing mathematics and science in action! Narrow straight molding (painted white to match the ceiling) placed on these lines (the entire width of the ceiling) to depict the hour lines, will make this dial discreetly decorative, yet functional. With the large amount of interest and enthusiasm generated by this topic, I'll have to take some photos during it's creation, and once completed, share them with the sundial group to demonstrate the whole process and it's success. Judith FYI... For those interested in HUMAN/GARDEN SUNDIALS as well (last summer's project with my children), I've created a fill-in worksheet that computes the calculations automatically in inches with longitude correction (for Northern Latitudes and Western Longitudes) -- one just needs to know their latitude (and optional longitude and time zone for correction), and the desired size. I've been working with John Hoy to have it posted at his website (http://www.cyberspace.org/~jh/dial/). I will be casting these sundials onto the area schoolyard blacktops in March (before Daylight Savings in April). I believe this community service project should be made available to all -- free of charge! -Original Message- From: Steve Lelievre [mailto:[EMAIL PROTECTED] Sent: Friday, January 04, 2002 9:58 AM To: sundial@rrz.uni-koeln.de Subject: Re: Ceiling Sundial I agree, John. At one solstice the EoT is about +2 minutes, and at the other it is about -2 minutes so there would be only a slight discrepancy. Too small to worry about, especially as this is a junior school project and Judith is trying to avoid too much complicated explanation. I like her approach for its simplicity, but there's one potential problem which I don't know how to solve. What happens if the summer dot is on the ceiling and the winter dot is on a wall? How do you draw the straight line connection? I can imagine the method being used by other teachers in the future, and people forgetting to take back Daylight Saving Time for the summer labels, or vice versa. Steve As it turned out (in my opinion), her original idea was correct. John I have the tiny lipstick mirror mounted at my window frame (half way up) , and was told that the easiest way (void of all the mathematical calculations that they would not understand) is to mark each hour in the day during the winter and summer solstices (12/21 and 06/21) -- then connect the dots. Granted this process takes six months to complete, but it would ensure that all longitude corrections are incorporated, effortlessly.
Re: Ceiling Sundial
Dear Dialists, So, it looks like Fer de Vries suggestion to use something, his program maybe, to at least be sure of the mirror placement being able to project all the hour lines and declination lines wanted on the ceiling rather than elsewhere is actually a very good idea. I've never tried this, it hasn't been sunny long enough to make it outside and check this, so far this winter, but it is an idea you can shoot up or down for me. (Assuming penlights and protractors are simple enough technically.) With a laser pointer or a penlight, a fair sized protractor and a mirror couldn't you by placing the protractor in the meridian shadow plane while in contact with the mirror positioned where you want it, then shine the light in from the window along the angle of latitude first plus maximum positive declination then minus maximum negative declination and from the spots shown on ceiling and wall at least tell if the full length of the analemma of the noon hour would fall fully on the ceiling? ( I couldn't find an easier way to say this ) Once done couldn't you then fasten down your mirror. If you then rotated the base of your protractor 90 degrees to be along the east west line and it's upper edge tilted to an angle measured on a piece of cardboard to be the latitude toward the window, couldn't you then by shining the light in from the window determine what hour lines would also be on the ceiling, and if wanted, rotate the mirror slightly to include a favored hour and then fasten it down again? ( each hour line being 15 degrees further from the meridian line ) Then, of course you could construct your hour lines as they occurred with paint or red thumbtacks or however you liked, knowing that the year's efforts would put the lines only where you wanted them. I've heard some strange stories about where some of the hour lines have ended up. (Of course use a protractor made of a non-scratching substance if your mirror is first surface on glass.) Enjoy the light, every minute of it. Edley McKnight [43.126N 123.357W]
Re: Ceiling Sundial
Andrew Pettit contributed, Is it likely to have helped Judith in her quest As one of the 'guilty parties' I take your point Andrew but surely a mailing list thread isn't just a straight QA device? It is an opportunity to share know-how on all aspects of the subject in hand with, hopefully, sufficient direct responses to the original query. You filter out the bits that are useful to you and discard the remainder. For instance there are several people now awaiting the JPEGs I offered on laser mounting so presumably this was of interest/relevance to them if not to Judith. As a 'know-how-ravenous' person myself I'd always rather have too much information than too little. Best Wishes Tony Moss
Re: Ceiling Sundial
All of these ideas using lasers, auxiliary sundials and transparencies all sound like they would help in drawing the sundial face, but I don't think they will precisely place the dial drawing on the ceiling or help to correctly align a declining or inclining mirror. I think you all are minimizing the importance of the optical lever effect. Very slight errors in placing the transparencies, lasers and auxillarily sundials can cause the sunspot on the ceiling to be way off. For example, let's consider a large room with a maximum sunspot projection distance from mirror to ceiling of say 25 feet (8 meters). Let's see how far off the sunspot will be if the mirror is tilted just 1 degree from where the design specs say it should be. (To make the math easier, imagine that the mirror is in the center of a sphere projecting a sunspot onto the interior wall of the sphere). A circle of a 25 ft. radius has a circumference of 157ft.or 1884 inches (4800 cm). So, 1 degree = 1884/360=5 in. (13 cm.) This shows that just a 1 degree error in mirror alignment causes an unacceptable 5 inch error in sunspot location. Misalignments of the laser, transparency or an auxiliary sundial would cause similar errors. (There might also be an additional error caused be the sunspot being refracted from passing through the glass window or from uneven surfaces or tilts in the ceiling) In my opinion, these layout and construction methods might help as as guide to roughly get an idea for the final look of the dial or as a check, but can not equal the precision and accuracy obtained by using the actual sunspot to draw the dial on the ceiling. I still think that the easiest and best way to draw a ceiling dial is to first permanently install and mount the mirror to its support structure, and then mark the center of the sunspot on the ceiling at different times, and connect the dots. 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
Re: Ceiling Sundial
On Thu, 3 Jan 2002, John Carmichael wrote: All of these ideas using lasers, auxiliary sundials and transparencies all sound like they would help in drawing the sundial face, but I don't think they will precisely place the dial drawing on the ceiling or help to correctly align a declining or inclining mirror. I think you all are minimizing the importance of the optical lever effect. Very slight errors in placing the transparencies, lasers and auxillarily sundials can cause the sunspot on the ceiling to be way off. All quite correct, as you put it, John. However, as I understand how John Lynes suggestion was meant, the mirror becomes an alignment and dial placement tool, not a critical design element: It seems easier to lay out and correctly orient an auxialiary dial, than to design and lay out a ceiling dial. The laser/mirror projection technique was suggested as a way of copying that auxiliary dial onto the ceiling, permitting the designer to place the resulting lines in a pleasing and useful manner by adjusting the mirror before finally fixing it in place. The optical lever effect is certainly a significant problem to consider, and we haven't addressed how to manipulate and eventually mount that little mirror, but I would imagine walking through the dates and times I wanted to see projected, pencilling the major points on the final surface, until I had the layout I wanted. Lock the mirror in place, then run through to re-check the placement. If necessary, shim the mirror, or just use it's final position to re-project the dial points, before painting the lines or whatever... Dave 37.29N 121.97W
Re: Ceiling Sundial
Dear Membership, I've been listening to all the great ideas about Ceiling dials and they all sound like they would work well under some circumstances. In earthquake country or where the soil shifts from moisture/freezing the mirror is going to have to be adjustable. If the dial is laid out with date lines as well as hour lines it would seem to be straight forward, although tedious to be able to align the bright spot with the correct time and date at any time and thus correct for many of the mentioned problems. An old friend, being also a professional seamstress, laid out her ceiling dial on tissue, going over the lines with a rolling perforator, tacked it to the ceiling with spray adhesive and pounced through the perfs with a bag of charcoal powder. This got her pretty close, but she didn't paint in the lines til the times actually came. She trusted a gap of a few hours if the hours on each side of it were good. Another, being a professional photographer took a picture of his horizontal dial on 35mm and then projected it on the ceiling aligned with a few check points obtained from the sun's mark from the mirror. Of course he understood all those factors of perspective and distortion and how to deal with them. I've not ever been so located that a ceiling dial is possible, although it sounds so neat that I may try an under the carport roof dial. I guess I'll use a piece of polished stainless steel rather than a first surface mirror, since I can polish it with car polish or tootpaste when the atmosphere fouls it. I really appreciate this list! Edley McKnight [43.126N 123.357W]
Re: Ceiling Sundial
Tony et al, In the case of the 3D pantograph by David the accuracy of the laser pointer itself isn't important. At first the beam is adjusted through the (nodus of) the style and a point on the dial. Then this beam is shifted parallel to itself until it shines on the mirror. The beam then is in the right position. Please send me the picture of your laser trigon. Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E - Original Message - From: Tony Moss [EMAIL PROTECTED] To: Sundial Mail List sundial@rrz.uni-koeln.de Sent: Wednesday, January 02, 2002 12:14 PM Subject: Re: Ceiling Sundial Dave Bell contributed I had been thinking about John Lynes' suggestion for using a laser pointer to copy rays from a horizontal dial (or any other type, for that matter) through a sill-mounted mirror to a ceiling dial. I'm attaching a (small!) sketch of the sort of 3D pantograph support it would take. I'd appreciate any suggestions from the machinists/mechanists out there, on making it workable! One practical caveat on the subject of laser pointers. The 'diode laser' these devices contain is unlikely to be mounted with any useful degree of precision as they are only intended as a hand-held pointer. Consequently the axis of the laser beam may well not align with the axis of the metal tube/case in which it is mounted. You can test this by placing the pointer in a vee-shaped trough (an engineers' vee block if you have one) and rotating it through 360° while holding it lightly in contact with the vee. If the spot projected on a distant wall remains in the same location you are lucky and alignment is spot on but if it describes a circle you can calculate its divergence from truly coaxial by noting the diameter of the circle and the distance of the wall. One simple corrective method used in the precision laser trigon I made for the 20 metre dia, Silverlink dial, where the dial 'plate' is a double cone, was to note the highest/lowest points of the inaccuracy circle and mount the device so that these lay in the plane of rotation of the trigon i.e. perpendicular to its pivot. In the final version of the laser trigon the pointer case was held in a vee groove milled/ground along a 60mm length of 16mm square steel block by a u-bolt which allowed rotary adjustment as above. The perpendicular bearing was again a vee groove milled/ground at right angles across the base of the steel block. A light leaf spring held this in contact with a ground cylindrical bar to provide a precision 'swinging laser' with absolutely no play in the joint. JPEG of the final device to anyone who contacts me directly. I love the lights of Paris I love the lights of Rome. But the finest of all are the tail lights Of the cars taking grandchildren back home. Just joking. Tony Moss
Re: Ceiling Sundial
I like it!! Printing the dial artwork on transparency film should work well. Rub it down onto a thin sheet of glass supported in a frame, perhaps with a film of water or the like to keep it in place. The frame would need to be accurately leveled and oriented, but could easily be clamped in position, once that is determined. One hitch might come in, if the mirror is placed on the inside sill of a fixed picture window, making it hard to get the dial center over the mirror... Dave 37.29N 121.97W On Wed, 2 Jan 2002, J Lynes wrote: Here's a simpler proposal. Transfer the declination lines and hour lines of a horizontal sundial onto a transparent sheet. Mark a small circle on the centre of the mirror. Support the horizontal transparent sheet, rotated from north to south, with its nodus vertically above the centre of the circle, at a distance equal to the height of the transparent sundial's gnomon. Project a laser beam through the transparent sheet onto the centre of the circle. Make sure the beam passes through the sundial scale at a point corresponding to some chosen time and date. The reflected spot on the ceiling is the appropriate point on the ceiling sundial. Repeat for other dates and times. John Lynes
Re: Ceiling Sundial
I had been thinking about John Lynes' suggestion for using a laser pointer to copy rays from a horizontal dial (or any other type, for that matter) through a sill-mounted mirror to a ceiling dial. I'm attaching a (small!) sketch of the sort of 3D pantograph support it would take. I'd appreciate any suggestions from the machinists/mechanists out there, on making it workable! Dave 37.29N 121.97W Content-Type: IMAGE/GIF; NAME=3D_Laser.gif Content-ID: [EMAIL PROTECTED] Content-Description: Content-Disposition: ATTACHMENT; FILENAME=3D_Laser.gif Attachment converted: Macintosh HD:3D_Laser.gif (GIFf/JVWR) (000393C1)
Re: Ceiling Sundial
Hi John and Everyone, John mentioned: Also, there is the additional problem of physically transferring Zw2000 drawings and /or polar coordinates of hour angles and dial furniture onto the ceiling. I too have a mirror on the sash of my window for a future sundial on the ceiling. Once you have the meridian line marked, I do not feel it would be a problem transferring Zw2000 drawing to the ceiling. I would make a full scale drawing in Corel Draw and then put it on a disk and take it to an architectural drafting business that do blue prints. They can print the dial in 3-foot sections as long as needed and then tape to the ceiling to mark the lines. I think there is even a better way. Wide format thermal transfer printing. Check out Thermal Transfer Solutions at www.t2-solutions.com I believe you can incorporate the Zw2000 drawing with artwork and just put it on the ceiling like wallpaper. I attended my first trade show of the United States Sign Council in Atlantic City for the sign industry. There are many possibilities for sundials using CNC routers, laser engraving, sublimation and all types of interior and exterior wide format printing. If you get a chance to attend one of their shows it would be well worth it and you will agree the sign industry has a lot to offer to sundial designers. Now if I only had time to work on the ceiling dial, Thanks. Ken Clark Elizabethtown, PA
Re: Ceiling Sundial
Here's an alternative approach, which would work best with two people: Set up a simple horizontal sundial, with declination lines, correctly oriented, beside the mirror, say a foot to one side. Using a laser pointer, or just a bare low-voltage filament lamp, cast a shadow of the gnomon onto the sundial scale at some chosen hour and declination. Move the laser pointer exactly one foot sideways to illuminate the centre of the mirror. Mark the position of the spot of light reflected onto the ceiling. This is the point on the ceiling sundial for the chosen hour and declination. Repeat for other hours and declinations. Note that this does not assume that the mirror is horizontal. Obviously the method could be simplified if declination lines are not wanted on the ceiling. Happy New Year! John Lynes
Re: Ceiling Sundial
Nice idea, John! Moving the laser pointer a precise distance horizontally isn't really necessary, nor exactly what you want. I think the requirement would be to move the pointer along whatever axes you need to, but without changing it's angular orientation. That way, you move from the pointer projecting one ray across the gnomon onto the dial plate, to a parallel ray through the pinhole mirror... Using this projection method, you could easily and quickly test where various lines would fit on the ceiling, and adjust the mirror to get the placement you want. Of course, any kind of master dial can be used, of any convenient size! Use one of the fine pieces of software distributed through NASS, make a paper horizontal dial with a long needle for style and nodus, and you can transfer as many points as you wish, to the ceiling, walls, whatever. Compare to Robert Terwilliger's Laser Trigon, and his Shadow Garden: http://www.shadow.net/~bobt/garden/garden.htm Dave 37.29N 121.97W On Mon, 31 Dec 2001, J Lynes wrote: Here's an alternative approach, which would work best with two people: Set up a simple horizontal sundial, with declination lines, correctly oriented, beside the mirror, say a foot to one side. Using a laser pointer, or just a bare low-voltage filament lamp, cast a shadow of the gnomon onto the sundial scale at some chosen hour and declination. Move the laser pointer exactly one foot sideways to illuminate the centre of the mirror. Mark the position of the spot of light reflected onto the ceiling. This is the point on the ceiling sundial for the chosen hour and declination. Repeat for other hours and declinations. Note that this does not assume that the mirror is horizontal. Obviously the method could be simplified if declination lines are not wanted on the ceiling. Happy New Year! John Lynes
Re: Ceiling Sundial
Hi Fer Thanks for pointing out the mirror sundial calculating feature of Zw2000. But I see a problem with using it in practice, however. Since a ceiling sundial uses a very small mounted mirror, I think that measuring the exact inclination and declination of such a small mirror would be very difficult when you are locating and mounting the mirror. Because of the optical lever effect, the slightest error in locating the mirror translates into a huge error on the dial's ceiling face, making the sunspot appear where it shouldn't. Also, there is the additional problem of physically transferring Zw2000 drawings and/or polar coordinates of hour angles and dial furniture onto the ceiling. These problems are eliminated when you use the connect the dot drawing method. 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
Re: Ceiling Sundial
The past year, I've been playing around with a little 1cm. square mirror to be used for ceiling sundials that Fred S. gave us at the Hartford NASS conference. I have a large room with a big ceiling. The roof of the house has an overhang over the southern window, however. In order that the level mirror not be shaded by the overhanging roof in the summer, I found that I had to lower the mirror closer to the floor. This of course caused the hour spots to be shifted far to the north on the ceiling. I wanted the ceiling dial face to be somewhat centered on the ceiling, but lowering the mirror shifted the hour lines too far north on the ceiling. I found that I could correct this by tilting it slightly to the south. Tilting the mirror will also help to center the dial face on a ceiling of a room that declines from south. Now, tilting the mirror makes calculating the hour lines mathematically very difficult (for me). But using the connect the dots method that we've been discussing greatly simplifies the drawing of the dial face. It just takes a long time (six months). 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
Re: Ceiling Sundial
Hi John, That's great to build a sundial on your ceiling. It isn't difficult to create the pattern with all kind of lines you want on your ceiling dial. Just use the program Zw2000, option mirror sundial. The mirror may have any inclination and/or declination you want and with some trial and error you will find the best solution for your room. The mirror is placed on the endpoint of the (imaginary) gnomon, of which the length should be known, pendicular to the ceiling. The ceiling itself also may have any declination and/or inclination, but usual this will be inclination 180, declination 0 degrees. Show us the result. Best wishes and a happy New Year. Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E - Original Message - From: John Carmichael [EMAIL PROTECTED] To: sundial@rrz.uni-koeln.de Sent: Saturday, December 29, 2001 3:30 PM Subject: Re: Ceiling Sundial The past year, I've been playing around with a little 1cm. square mirror to be used for ceiling sundials that Fred S. gave us at the Hartford NASS conference. I have a large room with a big ceiling. The roof of the house has an overhang over the southern window, however. In order that the level mirror not be shaded by the overhanging roof in the summer, I found that I had to lower the mirror closer to the floor. This of course caused the hour spots to be shifted far to the north on the ceiling. I wanted the ceiling dial face to be somewhat centered on the ceiling, but lowering the mirror shifted the hour lines too far north on the ceiling. I found that I could correct this by tilting it slightly to the south. Tilting the mirror will also help to center the dial face on a ceiling of a room that declines from south. Now, tilting the mirror makes calculating the hour lines mathematically very difficult (for me). But using the connect the dots method that we've been discussing greatly simplifies the drawing of the dial face. It just takes a long time (six months). 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
RE: Ceiling Sundial
I think that I would pick a day near the winter solstice, apply both the EoT AND longitude corrections for where I live and mark the hour spots. Repeat at the summer solstice. Then you would get the dial lines just like they are on (say) a horizontal dial. For example - the sun is shining today, and I live 3 degrees 2 seconds west of Greenwich EoT is 1 min 35 secs (dial slow) Longitude correction is 12 mins 8 seconds (dial slow) Total correction is therefore 13 mins 31 secs (dial slow) So mark the winter ends of the hour lines at 13 mins 31 secs after each hour all day. If you miss the odd one, try again tomorrow, with tomorrow's figures, the declination hardly changes at the solstices, so the spot will still be near the end of the line. Really easy if you have Bob Terwilliger and Fred Sawyer's Diallist's Companion programme. Mike Shaw http://homepage.ntlworld.com/jmikeshaw/ N 53º 21' 24 W 03º 01' 47 Wirral, UK.
Re: Ceiling Sundial
Ron, et al, Yes, I like (and now think I understand) your approach, alas, I wish I were patient enough. Namely, the hour angle of the Sun and its projection will be what they are and no correction need be applied since the EoT is zero and the hour angle delta between the local and standard meridians is constant. The approach I've taken in the past is to project the Analemma itself from computed local hour angle values. One might consider this approach for at least one of the hour-lines, as it is adds the satisfaction of an analytical approach to the measured approach that Ron has mentioned. Also, and IMHO, using the hour-line of the Analemma provides a more intuitive understanding. Regards, Luke Coletti Ron Anthony wrote: Mike, Luke, I was saying, on a few of the days that the EOT is 0, look at your watch and mark the ceiling right on the hour. And then connect all of the like hours dots you will build a dial that works and is corrected for longitude, but not EOT. The hour lines are simple straight ones, (that is of course if all the hour dots are on the ceiling). Someone had told her to use the winter and summer soltice as the days to mark the hour dots. That would be somewhat close, but not as accurate as the 4 days given. ++ron This is a bit confusing because I'm not sure I can tell what type of hour-lines are being considered here. Perhaps Ron was referring to the fact that if one constructs the hour-lines from the projection of the Analemma itself AND includes the delta in local longitude from the longitude of the standard meridian, then, the solar projection will indeed cross zero four times per year(?). I think this may be the more intuitive way of constructing such a sundial too, for the very reason that this thread makes clear. Regards, Luke Coletti The Shaws wrote: Ron wrote: I've never built a ceiling dial, but something doesn't sound right about the advice that you got. The days that you choose should be days where the equation of time is 0 (sun time and watch time agree). This happens 4 times a year. April 15, June 14, Sept 1, Dec 25. But clocks and dials DON'T coincide on these dates UNLESS you just happen to live on your prime meridian. If you want to apply the normal Equation of Time correction, you will have to work out which days coincide at your own longitude. Where I live (3 degrees West of Greenwich) clock and dial only coincide on 2 days a year. If you live more than about 5 degrees away from your meridian, they will never coincide. See: http://homepage.ntlworld.com/jmikeshaw/ and follow the link to Equation of Time slide rule first, and then Noon Mark Mike Shaw N 53º 21' 24 W 03º 01' 47 Wirral, UK. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.307 / Virus Database: 168 - Release Date: 11/12/2001
Re: ceiling sundial
Hello Reinhold, Very interesting, I used Altavista (URL below) to translate the URL you sent. Thank you. http://world.altavista.com/ Regards, Luke Coletti [EMAIL PROTECTED] wrote: Hello all, a good and easy way to build a ceiling-sundial is to use the Tridux 2000 by Dietrich Ahlers Please have a look at: http://www.hs-bremen.de/planetarium/astroinfo/sonnenuhren/ahlers/tridux.htm There will soon also be an English text for it. Best regards Reinhold Kriegler * ** *** * ** *** Reinhold R. Kriegler Lat: 53° 06' 53'' N Long: 8° 53' 54 E
RE: Ceiling Sundial
Ron wrote: I've never built a ceiling dial, but something doesn't sound right about the advice that you got. The days that you choose should be days where the equation of time is 0 (sun time and watch time agree). This happens 4 times a year. April 15, June 14, Sept 1, Dec 25. But clocks and dials DON'T coincide on these dates UNLESS you just happen to live on your prime meridian. If you want to apply the normal Equation of Time correction, you will have to work out which days coincide at your own longitude. Where I live (3 degrees West of Greenwich) clock and dial only coincide on 2 days a year. If you live more than about 5 degrees away from your meridian, they will never coincide. See: http://homepage.ntlworld.com/jmikeshaw/ and follow the link to Equation of Time slide rule first, and then Noon Mark Mike Shaw N 53º 21' 24 W 03º 01' 47 Wirral, UK. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.307 / Virus Database: 168 - Release Date: 11/12/2001
Re: Ceiling sundial
Both Ron Mike have got it almost right it seems.. If you intend to make a ceiling (or any other kind of dial) by connecting the hour points shown by the shadow of the nodus on at least two of the four days when EOT equals zero, then you would have a perfectly good dial that is automatically corrected for longitude. Wouldn't you? The two best days to mark the location of the nodus's shadow would be those dates that produce the longest lines when connected. ei. dates close to the solstices. Those dates would be December 25 and June 14. 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
Re: Ceiling Sundial
Hello Mike, This is a bit confusing because I'm not sure I can tell what type of hour-lines are being considered here. Perhaps Ron was referring to the fact that if one constructs the hour-lines from the projection of the Analemma itself AND includes the delta in local longitude from the longitude of the standard meridian, then, the solar projection will indeed cross zero four times per year(?). I think this may be the more intuitive way of constructing such a sundial too, for the very reason that this thread makes clear. Regards, Luke Coletti The Shaws wrote: Ron wrote: I've never built a ceiling dial, but something doesn't sound right about the advice that you got. The days that you choose should be days where the equation of time is 0 (sun time and watch time agree). This happens 4 times a year. April 15, June 14, Sept 1, Dec 25. But clocks and dials DON'T coincide on these dates UNLESS you just happen to live on your prime meridian. If you want to apply the normal Equation of Time correction, you will have to work out which days coincide at your own longitude. Where I live (3 degrees West of Greenwich) clock and dial only coincide on 2 days a year. If you live more than about 5 degrees away from your meridian, they will never coincide. See: http://homepage.ntlworld.com/jmikeshaw/ and follow the link to Equation of Time slide rule first, and then Noon Mark Mike Shaw N 53º 21' 24 W 03º 01' 47 Wirral, UK. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.307 / Virus Database: 168 - Release Date: 11/12/2001
Re: Ceiling Sundial
Mike, Luke, I was saying, on a few of the days that the EOT is 0, look at your watch and mark the ceiling right on the hour. And then connect all of the like hours dots you will build a dial that works and is corrected for longitude, but not EOT. The hour lines are simple straight ones, (that is of course if all the hour dots are on the ceiling). Someone had told her to use the winter and summer soltice as the days to mark the hour dots. That would be somewhat close, but not as accurate as the 4 days given. ++ron This is a bit confusing because I'm not sure I can tell what type of hour-lines are being considered here. Perhaps Ron was referring to the fact that if one constructs the hour-lines from the projection of the Analemma itself AND includes the delta in local longitude from the longitude of the standard meridian, then, the solar projection will indeed cross zero four times per year(?). I think this may be the more intuitive way of constructing such a sundial too, for the very reason that this thread makes clear. Regards, Luke Coletti The Shaws wrote: Ron wrote: I've never built a ceiling dial, but something doesn't sound right about the advice that you got. The days that you choose should be days where the equation of time is 0 (sun time and watch time agree). This happens 4 times a year. April 15, June 14, Sept 1, Dec 25. But clocks and dials DON'T coincide on these dates UNLESS you just happen to live on your prime meridian. If you want to apply the normal Equation of Time correction, you will have to work out which days coincide at your own longitude. Where I live (3 degrees West of Greenwich) clock and dial only coincide on 2 days a year. If you live more than about 5 degrees away from your meridian, they will never coincide. See: http://homepage.ntlworld.com/jmikeshaw/ and follow the link to Equation of Time slide rule first, and then Noon Mark Mike Shaw N 53º 21' 24 W 03º 01' 47 Wirral, UK. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.307 / Virus Database: 168 - Release Date: 11/12/2001
Re: Ceiling Sundial
Judith, I've never built a ceiling dial, but something doesn't sound right about the advice that you got. The days that you choose should be days where the equation of time is 0 (sun time and watch time agree). This happens 4 times a year. April 15, June 14, Sept 1, Dec 25. (sorry I should have written this earlier) If you mark the hours on these 4 dates they will form a straight line when connected. I know I haven't given you much to go on, but I think the people on the list will agree. Please email if you have any questions. Good luck ++ron - Original Message - From: Romano, Judith [EMAIL PROTECTED] To: sundial sundial@rrz.uni-koeln.de Sent: Thursday, December 20, 2001 7:04 AM Subject: Ceiling Sundial Hello Sundial Friends: I am planning on making a ceiling sundial (as a project with my children in an actual science/math application). I have the tiny lipstick mirror mounted at my window frame (half way up), and was told that the easiest way (void of all the mathematical calculations that they would not understand) is to mark each hour in the day during the winter and summer solstices (12/21 and 06/21) -- then connect the dots. Granted this process takes six months to complete, but it would ensure that all longitude corrections are incorporated, effortlessly. Any opinion or comments today, from anyone who has done one, would be quite helpful, (as this process is to start tomorrow)! Thanks! J Romano
