Hello all: The reason that I inquired as to when the Equation of time equals zero is because I state in my Sundial owner's Manual that on these four days (Apr 15, Jun 14, Sep 1, and Dec 25) my sundials need no EOT correction. I realize that this statement is not entirely correct as the date when EOT=0 depends on the specific longitude of the observer. For example, this year, EOT=0 early in the morning in Greenwich on Apr 16th but late at night on the 15th here in the US.
Also, I asume that the exact time when EOT=0 must vary slightly from year to year. Does anybody know what the maximum amount of variation would be? Is it more than 24 hours? Several people wrote me with their calculations of when EOT=0. I hope they don't mind if I sumerize their answers for you here. Jim Cobb: 4/16/1999 3:04:36 UTC (xephem version 3.0) Luke Coletti: 4/16/1999 0:40:00 UT (Solar Calculator) Jean-Paul Cornec: 4/16/1999 1:06:04 UT (VSOP87) James Morrison: 4/16/1999 0:40:57 UT (?) As you can see, all the calculations are different. I assume this is due to the different calculating methods that were used. Surely there can only be one correct answer.(Or should I use the average time of all the answers?) Thanks again to Jim, Luke, Jean-Paul, and James for taking the time to do the calculations. John Carmichael Tucson
