Having spent an inordinate amount of time comparing the LBR values of Meeus (Astronomical Algorithms 1998) vs. ELP82B (Chapront's ELP82b Fortran Program) I have figured out the data set I'm using is according to J2000 to wit:
Lambda for the Moon on Julian day: 1241387.69306 is 179°30'48.3" acc. to Meeus
Lambda for the Moon on J2000 is 225°45'0.3" acc. to ELP82b
I would like to convert the position for J2000 for day: 1241387.69306 to be the position at the date and not J2000. I thought I might convert my jde: thus:
jde = (jde-2451545.0) / 365.25
but alas I'm not getting the right numbers.... what am I missing?
b1315-Sep-26 04:38:00.384 1241387.693060000 31055.468561 184.4309494 4.1332279
, where the last 3 fields are TDB-UT, Observer Ecliptic Longitude, and Observer Ecliptic Latitude, respectively. That's for the Moon (301) as the target, with the observer at the centre of the Earth (500@399). TDB-UT is the difference between Barycentric Dynamical time and Universal Time, in seconds. Please see the Horizons docs for further details. $\endgroup$