THIS is the kind of thing I have been looking for! The kinds of techniques that make the complex math work simply.
Cathedrals were built a thousand years ago by people who had little more literacy than needed to do their jobs. None of them knew what a sine or cosine or tangent was. They knew how ratios worked and they knew the practicalities of geometry. Thanks for the great tool. As it happens, I need to measure the declination of a wall and this helps a lot! Karon Adams Accredited Jewelry Professional (GIA) You can send a free Rosary to a soldier! www.facebook.com/MilitaryRosary www.YellowRibbonRosaries.com From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On Behalf Of Bill Gottesman Sent: Monday, August 01, 2011 10:55 AM To: sundial@uni-koeln.de Subject: Re: Azimuth calculation/Wall declination About 10 years ago I worked out a simple method to measure wall declination using just a carpenter's square and an accurate watch. The methods is described here http://www.precisionsundials.com/wall%20declination.pdf, and a simple windows program that does all the calculations for you is here http://www.precisionsundials.com/walldeclination.exe. When I tested it out many years ago, I believe it gave results repeatable at different times and on different days to a few tenths of a degree. -Bill On 7/31/2011 9:57 AM, Andrew Theokas wrote: Fellow dialists: I am using the following well known formula to calculate the sun’s azimuth for a particular time and location: Azimuth= tan-1 (sin H/(sin φ*cos H – cos φ*tanδ) where H= Sun’s hour angle φ= the latitude - 42.3 degrees δ is the sun’s declination - 18.62 degrees The location is in Boston, USA or 42.3 degrees N and 71.04 degrees west I am using the azimuth-azimuth approach to find the declination of a wall found here: http://www.mysundial.ca/tsp/wall_declination.html the time the measurement was made was 11:18 am (daylight savings time is in effect) I can easily calculate that the azimuth with respect to the wall is 26.8 degrees. Here is the problem: using two other independent methods I find that the wall’s declination is 20 degrees East. So 26.8 degrees – Sun’s Azimuth should equal about twenty degrees. But, using the above equation I cannot get an Azimuth value to work. One place where I might be in error is the value of the Hour angle which I compute to be about –16 degrees. But you can also find the Hour Angle on line here at http://pveducation.org/pvcdrom/properties-of-sunlight/sun-position-calculator Where might I be going wrong? Many thanks for a reply! Andrew Theokas --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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