In a message dated 1/26/2001 7:31:03 AM Eastern Standard Time, [EMAIL PROTECTED] writes:
> This was at 10:30 am, and luckily the sun was shining - but they were not > prepared to stand around until 12:24 pm - local apparent noon on that day. Congratulations Mike on using an ancient instrument to quickly solve a modern day problem. Given the situation you described, I propose the following method for determining the North South line with good accuracy at any time of the day. It works by measuring the sun's azimuth at a given time: Hang a string for use as a vertical plumb bob over a level surface, carefully mark the orientation of the shadow, and read the precise time off of an accurate watch. Then calculate the sun's azimuth for that time/date/location (this is easily done by plugging the appropriate values into Bob Terwilliger's and Fred Sawyer's Dialist program provided by the North American Sundial Society. Otherwise be prepared to get out your calculator, an EoT and Declination table, and the azimuth formula cot(Azimuth)=[sin(Latitude) x cos(Local Solar Time) - cos(Latitude) x tan(Declination)]/sin(Local Solar Time)). You have now accurately determined the orientation of that shadow line, and using a protractor or other means, can readily mark the North/South meridian. Bill Gottesman Burlington, VT
