Op 31-mrt-2006, om 4:28 heeft Shriramana Sharma het volgende geschreven:
> Jean Meeus in his Astronomical Algorithms (second edition) page 344
> gives
> some terms to be calculated to obtain the correction to the mean
> lunar node
> to obtain the longitude of the true lunar node. However, he
> specifies that
> there are only principal terms, indicating that there are other
> terms as
> well. Meeus mentions that the full terms are available in:
>
> M. Chapront-Touze and J. Chapront, Lunar Tables and Programs from
> 4000 BC to
> AD 8000, Willmann-Bell 1991.
>
> So if anyone has access to this book, perhaps via a library, and
> also the
> kindness and time to help me out here, I would be much grateful.
I do have that book.
There are several ways to represent ephemerides. One is to develop
series for the positions and velocities in 3 spatial coordinates.
Another is to develop series that will give six independent
"osculating" orbital elements valid for a specific moment in time:
the position at that instant can then be computed from the orbital
elements using Kepler's formulae.
So for the longitude of the ascending lunar node on the mean ecliptic
of the date (their p.27 and p.82):
Omega = 125.0446 - 1934.13618*t + 20.76210E-4*t**2 +2.139E-6*t**3
-1.650E-8*t**4 +
-1.4979*sin( 49.1562 -75869.8120*t +35.458E-4*t**2 +4.231E-6*t**3
-2.001E-8*t**4) [2D-2F]
-0.1500*sin(357.5291 +35999.0503*t -1.536E-4*t**2 +0.041E-6*t**3 ) [l']
-0.1226*sin( ... ) [2D]
+0.1176*sin( ... ) [2F]
etc.
(all angles in decimal degrees)
HTH,
--
Tom Peters
