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Re: (meteorobs) algorithm for Solar Coordinates (including sun's true longitude)
Jerry&Judy and the rest of the list,
This question, that of UT to Solar Longitude (and the reverse too), caused
me to pull out my copy of "Astronomical Algorithms" by Jean Meeus. The
algorithm given looks like it was lifted directly from Chapter 24, Example
24.a
>Let me know if this is accurate enough.
>
> Solar Coordinates
> This algorithm is capable to calculate the geocentric position of
> the Sun with an accuracy of 0.01 degree. ...
I've been wondering exactly this same question. Which method will give
enough accuracy? The method given from Chapter 24a, the higher accuracy
method in 24b, the mean longitude from Chapter 30, or the VSOP87
computation from Chapter 31.
An accuracy of 0.01 degree translates to approximately 15 minutes. While
this is probably accurate enough for meteor work, is it correct to use the
GEOmetric longitude and reverse that back as the SOLAR longitude?
If the VSOP87 algorithm is used, this computes the ecliptical longitude and
latitude, for the ecliptic of date (J2000.0). Once again a question of
accuracy, can the small but non-zero latitude for the Earth be ignored?
Jerry&Judy, did you find the algorithm online? Are the periodic terms for
VSOP87, reprinted in Meeus as Appendix II, available online?
I've been playing with PERL scripts and would love to build an appropriate
web page to compute these values, but I want to start with the correct
algorithm. Anyone out there have answers?
Gregg Lobdell
gml@halcyon.com
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