Wedding Rings

Info on sundials

Question:

Anyone know about a source of information on constructing sundials?  I am not sure if this is the proper newsgroup to post, but I will try anyway. Thanks <<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>                Bruce A. Bowling   Staff Scientist – Instrumentation and Controls  The Continuous Electron Beam Accelerator Facility     12000 Jefferson Ave – Newport News, VA 23602                  (804) 249-7240 <<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Response:

>Anyone know about a source of information on constructing >sundials?  I am not sure if this is the proper newsgroup >to post, but I will try anyway.

To construct a sun dial:  Put a stick in the ground.  Every hour, on the hour, put a rock at the tip of the shadow.  You have just created a sundial that is quite accurate on the day of construction. As the seasons change, move the rocks weekly or monthly (depending on your need for precision). For extra credit:  Make the stick into a triangle shaped thingy that is straight up and down on the ‘away from the sun side’ and has a slope on the ‘toward the sun side’. For extra extra credit:  Use different colored stones for each monthly calibration.  After one year of calibrations, connect the stones with lines of (stone, sand, paint, whatever) such that there is an arc punctuated by the monthly marker stones.  Now you have a sun dial that is accurate on any date, provided you now how far into the month you are and can look that far along the arc between the stones… If you are not willing to put in the time to calibrate over a year interval, then visit the library and look up ’sundials’.  If you are not willing to do that, then go to the local ‘yuppy’ garden supply store and buy a sundial.  Copy it.   If all else failes, call Real Goods at their 800 number and they have sundials for sale mail order.  (Including this very interesting portable one.  It is a ring like a giant wedding band with a hole drilled in the side.  It dangles from a string.  By adjusting the angle of the hole relative to the ‘angle of the dangle’ based on the month, the spot of light from the hole shines on the time on the inside of the ring oposite the hole.  {Or, alternativly, by having arcs oposite the hole calibrated by month.} This sundial depends on the asension angle of the sun changing over the course of the day, and not on the East/West angle.  It is convenient in that you need not know which way North is to use it…) — E. Michael Smith Manager of Stuff Cygnus Support

Response:

>|> To construct a sun dial:  Put a stick in the ground.  Every hour, >|> on the hour, put a rock at the tip of the shadow.   >If you go to the trouble of making the side of your triangle thingy point toward >the pole star, then the calibration you made today will be accurate within >several minutes for the rest of the year. … >that it gets complicated. [How much extra credit do I get?]

A+, an added 100 points, and move to the head of the class! — E. Michael Smith Manager of Stuff Cygnus Support

Response:

|> > |> >Anyone know about a source of information on constructing |> >sundials?  I am not sure if this is the proper newsgroup |> >to post, but I will try anyway. |> |> To construct a sun dial:  Put a stick in the ground.  Every hour, |> on the hour, put a rock at the tip of the shadow.  You have just |> created a sundial that is quite accurate on the day of construction. |> |> As the seasons change, move the rocks weekly or monthly (depending |> on your need for precision). |> |> For extra credit:  Make the stick into a triangle shaped thingy that |> is straight up and down on the ‘away from the sun side’ and has a |> slope on the ‘toward the sun side’. |> |> For extra extra credit:  Use different colored stones for each |> monthly calibration.  After one year of calibrations, connect the |> stones with lines of (stone, sand, paint, whatever) such that |> there is an arc punctuated by the monthly marker stones.  Now |> you have a sun dial that is accurate on any date, provided you |> now how far into the month you are and can look that far along |> the arc between the stones… |> |> If you are not willing to put in the time to calibrate over a year |> interval, then [...] If you go to the trouble of making the side of your triangle thingy point toward the pole star, then the calibration you made today will be accurate within several minutes for the rest of the year. This is because the time-of-day determines the east-west position of the sun and the time-of-year determines the north-south position. An edge parallel to the axis of the Earth casts a shadow that depends on the east-west position, but not the north-south position. After that it gets complicated. [How much extra credit do I get?] Art Carlson — To study, to finish, to publish. — Benjamin Franklin Dr. Arthur Carlson Max Planck Institute for Plasma Physics Garching, Germany

Response:

– Hide quoted text — Show quoted text ->Anyone know about a source of information on constructing >sundials?  I am not sure if this is the proper newsgroup >to post, but I will try anyway. >Thanks ><<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >               Bruce A. Bowling >  Staff Scientist – Instrumentation and Controls > The Continuous Electron Beam Accelerator Facility >    12000 Jefferson Ave – Newport News, VA 23602 >                 (804) 249-7240 ><<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

There is a group of individuals who have formed the North American Sundial Society, of which I am a member. They publish information on sundials on a monthly basis and are putting together a registry of sundials around the country. Contact: Fred Sawyer 8 Sachem Dr Glastonbury, CT  06033 Robert Terwilliger 2398 SW 22nd Ave Miami, FL  33145 A good book available from Dover is: SUNDIALS: Their Theory and Construction by Albert Waugh, $5.95 I got my copy from the Nature Company at a local mall. Good Luck – Chuck Ritz – ME Dept, Cal Poly Pomona

Response:

sci.physics and sci.astro folks: This is a thread that started on sci.energy.  I thought you all might want a crack at it. PCS

– Hide quoted text — Show quoted text -ng) writes: >|> > >|> >Anyone know about a source of information on constructing >|> >sundials?  I am not sure if this is the proper newsgroup >|> >to post, but I will try anyway. >If you go to the trouble of making the side of your triangle thingy point toward >the pole star, then the calibration you made today will be accurate within >several minutes for the rest of the year. This is because the time-of-day >determines the east-west position of the sun and the time-of-year determines the >north-south position. An edge parallel to the axis of the Earth casts a shadow >that depends on the east-west position, but not the north-south position. After >that it gets complicated. [How much extra credit do I get?] >Art Carlson >–

A few things bother me about this. 1)  If you are using the position of the shadow from the point of your triangle to indicate the time then the sides leading up to this point would not make a difference as it might just as well be a sphere suspended in space. I therefore don’t understand the statement about aligning "the side of your triangle thingy" to the pole star.  This is assuming of course that the dial is level and oriented north-south. 2)  If someone lived on the equator then the time of day would be simply and east west position of the shadow, but I don’t think this is the case at other latitudes.  Bear with me on the explanation.  (pls read carefully before flaming)         Imagine we are in the middle of a celestial sphere. Depending on the time of year the sun will be above or below the celestial equator (the projection of the earths equator on the celestial sphere).  The important point here is that all of the possible positions of the sun on this sphere for a given time of day would form an arc that if extended would be a great circle on this celestial sphere intersecting the celestial poles.  The plane defined by this circle would also intersect the center of the sphere.  Now that is where we are, at the center of this sphere, so at 3:00 for example at various times of the year the shadow positions through the year would be the intersection of the aforementioned plane with the horizontal plane of the sundial.  The intersection would be a line yes but this line would only run north-south for an observer at the equator.  If you live on one of the poles, this line would make an angle (relative to north-south) corresponding to the hour-angle of the sun.  For those of us at mid-latitudes it would make some intermediate angle. 3)  A minor point that strikes me as odd too is that when I calculated the zenith of the sun for various times of the year it varied by just short of 5 minutes (clock time) from solstice to solstice.  I don’t know where this variation from solar to clock time comes about so I guess I’ll post this to sci.physics and sci.astro to see if they can shed some light. (so to speak) Preston Smith Univ. of Illinois Dept. of Nuclear Engineering

Response:

>If you go to the trouble of making the side of your triangle thingy point toward >the pole star, then the calibration you made today will be accurate within >several minutes for the rest of the year. This is because the time-of-day

Correction to sundial is up to 16 minutes at various times of the year due to the earth’s elliptical orbit.  I think there is a FAQ in sci.astro for this. Rolf Meier                                      usual disclaimer applies

Response:

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