PeterO wrote: > The > technique can be in error by up to 30 degrees because of seasonal changes in > daylight hours. ??? 30 degrees is two hours of sun movement. The only significant change in time that I can think of is the equation of time and that only varies by about 30 minutes (+16, -14 or so). Are you confusing the 30 minutes with thirty degrees? > Can anyone tell me if it would be more accurate to proceed as follows? Start > off by calculating the time of day midway between sun rise and sunset (T1 in > 24 hour format). Then calculate T2 (12 hr format) = (Time of day [24 hr > format] - 12 - T1). Then orient the watch so that T1 faces the sun and > bisect the angle between T1 and T2. Sounds about right. If you want more accuracy, use local and not standard time - in other words, shift by the number of minutes of time between your longitude and the nearest standard time longitude (15 degrees of longitude = 1 hour). For example, I live about 17 minutes west of the standard time longitude, so the standard time for noon is 17 minutes off the true local time. You can also take into account the equation of time. I've never been too keen on these watch-based approaches. Depending on where you live and when you do it, it can be unreliable. For example, if you are in north Australia and the sun is on the Tropic of Capricorn, you'd have a hard time reliably locating the sun as "north". If you are on the tropic on that day, the sun is directly overhead and you can't use it at all (you end up standing in your shadow). That said, I usually just look at the sun and note the time (correcting for DST). Then I figure out the time difference to noon and then figure out the distance the sun has to travel (morning) or has traveled (afternoon) relative to noon (15 degrees per hour) and mentally swing that off to find south. As an aid, your palm, at arms length, is about 10 degrees wide. This is more useful in a world of digital watch displays. Mike *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Mon Nov 27 2006 - 05:41:13 PST
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