[Kstars-devel] Update Moon position to Meeus 1998

[Daniel-Marian Baboiu]

I noticed on the TODO list a "large project" for updating Moon
calculation to Meeus 1998. I think this item should be removed from the
list, because

1) I do not have Meeus 1998, but I found some code for Moon position
implementing it (or so it says). The algorithm and data files are
identical with the current kstars implementation (if I didn't blink...)

2) I checked the accuracy of Moon position calculated using the series
truncated by Meeus (60 terms each: latitude, longitude, distance) and
the full ELP2000-82b series (39000 terms overall). The differences in
position are as follows (standard deviation/maximum deviation):

            Meeus           
Longitude: 2.71"/18.25" 
Latitude:  1.01"/5.73"  
Distance:  2.96/14.23km 

There are a few subtle differences between various versions of ELP2000,
but that's beyond the point at the moment (although I can explain, if
necessary).

I noticed some authors using larger number of terms, something like 125
for longitude and distance, and 75 for latitude, but I didn't look at
the accuracy of those.