Comments on: Aquitaine Sundial Ring http://watchmakingblog.com/2008/12/08/aquitaine-sundial-ring/ A mechanical watchmaker in a digital world Sat, 11 Feb 2012 01:33:35 +0000 hourly 1 http://wordpress.org/?v=3.0.5 By: Tick Talk » 11 Great Stocking Stuffers for 2011 http://watchmakingblog.com/2008/12/08/aquitaine-sundial-ring/comment-page-1/#comment-48592 Tick Talk » 11 Great Stocking Stuffers for 2011 Sun, 11 Dec 2011 07:12:00 +0000 http://watchmakingblog.com/?p=632#comment-48592 [...] documented here on the blog back in 2008, the first time I ever encountered a sundial ring was the Aquitaine Sundial Ring my father gifted [...] [...] documented here on the blog back in 2008, the first time I ever encountered a sundial ring was the Aquitaine Sundial Ring my father gifted [...]

]]> By: J.Edwards http://watchmakingblog.com/2008/12/08/aquitaine-sundial-ring/comment-page-1/#comment-25305 J.Edwards Mon, 27 Dec 2010 17:42:47 +0000 http://watchmakingblog.com/?p=632#comment-25305 @Hatcher Align the hole in the center ring with the according letter of the current month on the outside of the ring. Position the ring so that the sun shines through the hole onto the inside of the ring. The position of the pinpoint of light on the inside of the ring indicates the time. @Hatcher Align the hole in the center ring with the according letter of the current month on the outside of the ring. Position the ring so that the sun shines through the hole onto the inside of the ring. The position of the pinpoint of light on the inside of the ring indicates the time.

]]> By: hatcher http://watchmakingblog.com/2008/12/08/aquitaine-sundial-ring/comment-page-1/#comment-25273 hatcher Mon, 27 Dec 2010 02:36:37 +0000 http://watchmakingblog.com/?p=632#comment-25273 i have one but i dont know how to read it. i have one but i dont know how to read it.

]]> By: Dan http://watchmakingblog.com/2008/12/08/aquitaine-sundial-ring/comment-page-1/#comment-13290 Dan Thu, 05 Nov 2009 18:44:07 +0000 http://watchmakingblog.com/?p=632#comment-13290 The first record of a sundial comes from the chaldean astronomer Berossus in 300 B.C. His sundial was a hollow half-sphere that had a bead-shaped pointer. During the day the shadow of the bead moved in a circular arc across the inner surface of the sphere. This arc was divided into twelve equal parts, and were called temporary hours because they changed with the seasons. Equal hours were only decided upon when clocks came into common use in the 13th century. The accuracy of a sundial (when compared to a watch or clock) will depend on several things. First, the sundial always reads standard time. When daylight time is in effect, you must add one hour. Second is your longitudinal position in relation to your time zone meridian. For instance, if you live in the Central Time Zone the meridian is 90° (Atlantic is 60°, Eastern is 75°, Mountain is 105°, Pacific is 120°, etc.). Every 15° of longitude equals 1 hour of time, so for every degree you move west of your time zone’s meridian you need to add 4 minutes to the sundial’s apparent time (when you move east of the meridian you will need to subtract 4 minutes for each degree). Third is the angle of the pointer (or gnomon). For accurate time, the angle must be the same as the latitudinal position. A sundial located in eastern Ontario, for instance, needs to have the gnomon set to an angle of 45°. In southern Ontario the angle might be 42° and in the prairies 50°. Most manufactured sundials (including the Aquitaine ring) are set to an average angle of 40°. Last is the correction for the equation of time. Because the earth’s orbit around the sun is not perfectly circular, there will be deviations in the speed of the sun’s motion across the sky from season to season. The two most extreme points are in February when you must add 15 minutes to the apparent sundial time, and early November when you must subtract 15 minutes. Most of the spring and summer months are accurate to within 5 minutes. It is clear that even a clock will not give you the true reading of time for your location, because the same time is used within a 15° longitudinal area. The sundial is precise without being accurate, while a clock is accurate without being precise. Regardless of all the variables, if you have two sundials that are made the same and reading time in the same location, then they will display the same time. That, if nothing else, is reassuring. -------------------------------------------------------------------------------- ©Copyright 1998 to 2009 by Lee Valley Tools Ltd. and Veritas® Tools Inc. All rights reserved. The first record of a sundial comes from the chaldean astronomer Berossus in 300 B.C. His sundial was a hollow half-sphere that had a bead-shaped pointer. During the day the shadow of the bead moved in a circular arc across the inner surface of the sphere. This arc was divided into twelve equal parts, and were called temporary hours because they changed with the seasons. Equal hours were only decided upon when clocks came into common use in the 13th century.

The accuracy of a sundial (when compared to a watch or clock) will depend on several things. First, the sundial always reads standard time. When daylight time is in effect, you must add one hour.

Second is your longitudinal position in relation to your time zone meridian. For instance, if you live in the Central Time Zone the meridian is 90° (Atlantic is 60°, Eastern is 75°, Mountain is 105°, Pacific is 120°, etc.). Every 15° of longitude equals 1 hour of time, so for every degree you move west of your time zone’s meridian you need to add 4 minutes to the sundial’s apparent time (when you move east of the meridian you will need to subtract 4 minutes for each degree).

Third is the angle of the pointer (or gnomon). For accurate time, the angle must be the same as the latitudinal position. A sundial located in eastern Ontario, for instance, needs to have the gnomon set to an angle of 45°. In southern Ontario the angle might be 42° and in the prairies 50°. Most manufactured sundials (including the Aquitaine ring) are set to an average angle of 40°.

Last is the correction for the equation of time. Because the earth’s orbit around the sun is not perfectly circular, there will be deviations in the speed of the sun’s motion across the sky from season to season. The two most extreme points are in February when you must add 15 minutes to the apparent sundial time, and early November when you must subtract 15 minutes. Most of the spring and summer months are accurate to within 5 minutes.

It is clear that even a clock will not give you the true reading of time for your location, because the same time is used within a 15° longitudinal area. The sundial is precise without being accurate, while a clock is accurate without being precise. Regardless of all the variables, if you have two sundials that are made the same and reading time in the same location, then they will display the same time. That, if nothing else, is reassuring.

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©Copyright 1998 to 2009 by Lee Valley Tools Ltd. and Veritas® Tools Inc. All rights reserved.

]]> By: J.Edwards http://watchmakingblog.com/2008/12/08/aquitaine-sundial-ring/comment-page-1/#comment-4151 J.Edwards Wed, 10 Dec 2008 02:26:09 +0000 http://watchmakingblog.com/?p=632#comment-4151 Thanks J.Peter! Thanks J.Peter!

]]> By: J.Peter http://watchmakingblog.com/2008/12/08/aquitaine-sundial-ring/comment-page-1/#comment-4128 J.Peter Tue, 09 Dec 2008 04:30:30 +0000 http://watchmakingblog.com/?p=632#comment-4128 Happy Birthday Happy Birthday

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