See "Astronomical Algorithms" by Jean Meeus, pp 135-6. It is recommended
for astronomical calculations. The "Astronomical Almanac" probably has
values also.
The mean obliquity is (defined by the International Astronomical Union):
23 deg 26'21".448 - 46".8150 T - 0.00059 T^2 + 0".001 813 T^3
where T is in Julian centuries from J2000.0. This is the angle between the
ecliptic and the mean equator.
The angle with the true equator, the true obliquity, is also given,
differing by the nutation in obliquity. In the example given they differ by 9".
Gordon
At 10:26 AM 4/12/00 -0400, Robert Terwilliger wrote:
Question: Is there a source, or value, for the exact inclination of the
earth's axis? I understand it is decreasing slightly. The last value I
used was 23.4385 degrees. I cannot remember where I got it.
Bob
Gordon Uber [EMAIL PROTECTED] San Diego, California USA
Webmaster: Clocks and Time: http://www.ubr.com/clocks
