Bill, As the help file with the Dialist's Companion points out, this measurement is only approximate in this software package. In fact, however, equinoxes and solstices are not defined astronomically in terms of the sun's declination - they are defined in terms of its true longitude. This is noted in the help file. Using a zero declination to denote equinox only gives you an approximation. So you should really be viewing the equinox as the time when the zodiac indicator changes from virgo to libra. According to the Dialist's Companion, this happens at 19:06:53 which is pretty good considering that the help note suggests that this measure should only be considered good to within about ten minutes (solstices are more difficult than equinoxes).
Fred Sawyer ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, August 10, 2001 9:27 PM Subject: Equinox discrepancy > I was looking up the time of the autumnal equinox this year, using the NASS > dialist companion (version 1.1) to determine when declination=0. The value > (approximately 18:40 Eastern Daylight time on 9/22) differs by 25 minutes > from the value given at most other websites (such as > http://www.archaeoastronomy.com/almanac.html), being around 19:05 Eastern > Daylight Time. Any one know why there is a discrepancy? > > Bill Gottesman > Burlington, VT > 44.4674N, 73.2027W >
