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GHA Aries and GHA and Declination of the Sun
From: Bill Murdoch
Date: 1997 Dec 17, 9:35 PM
From: Bill Murdoch
Date: 1997 Dec 17, 9:35 PM
Woops. There is a mistake in the date part of the GHA Aries and sun GHA and declination calculation forms that I posted a week or two ago. I slipped up. The year 2000 is a leap year, so an extra day of 86,400 seconds has to be inserted after February 29. I modified the form and a new copy is attached. If you find any other mistakes, let me know. For someone who wants to put the formulas a program, there is an easy way to convert customary time and date to centuries before and after 1200 1 Jan 2000. It comes from Van Flandern and Pulkkinen, Low Precision Formulae for Planetary Positions, The Astrophysical Journal Supplement Series, vol 41, p 391, (1979). It works from March 1900 through February 2100. They also have another formula for longer lengths of time. T = (367*yr-trunc(7*(yr+trunc((mo+9)/12))/4) +trunc(275*mo/9)+day+(hr+(min+sec/60)/60)/24 -730531.5)/36525 The function trunc is just like trunc in Excel. It drops the fractional part of the number. trunc(8.9) = 8, trunc(-8.9) = -8. Bill Murdoch Kingsport, Tenn.