Questions tagged [ephemerides]

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7
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1answer
115 views

What are the problems that need to be taken in consideration when trying to find planetary position by using jpl ephemerides?

I'm currently trying to determine the position of the sun and the moon from jpl ephemeris DE200 which is referred to the dynamical equator and equinox of 2000 and uses tdb time. I am using the j2000 ...
2
votes
1answer
89 views

JPL Horizons - how to format TLIST input times for Email query?

I am trying to get a list of all of Mercury's Perihelia and Aphelia over a period of multiple decades. For each event I need X,Y,X and Vx,Vy,Vz data. Knowing the time of the first event it is easy to ...
6
votes
1answer
90 views

Determination of High-Accuracy Distances of Terrestrial Planets from the Sun

I understand how in olden days the Sun-Planet distances were estimated using:- (i) measures of planet orbital periods ($T$) from analysis of observations over several centuries; (ii) Kepler's 3rd ...
3
votes
1answer
346 views

Difference in Ephemerides Position:- PlanEph 4.2 (VSOP87) vs JPL Horizons (DE431)

I have obtained the hindcast position of Mercury relative to the Sun for the epoch 2000-Jan-01 12:00:00 using two methods: PlanEph ver 4.2 (Dos-based) and JPL Horizons DE431 (online). The two methods ...