Bob,
Yes, within the yearly information header of my WWW Solar Calculator
(URL below) I report the true obliquity at JAN 1.0 of the year being
evaluated (the longitude of perihelion as well as the date/times of the
solstices/equinoxes for the year are included too). So if you just need
to get the value(s) you can get it there. Note the true obliquity
differs from the mean obliquity, this effect is termed nodding or
nutation and is caused by the moon superimposing an oscillation on the
axis with a period of roughly 19yrs.
http://www.gcstudio.com/suncalc.html
-Luke
Robert Terwilliger wrote:
<snip>
> 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
