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JEphem Ephemeris trail Handling precision |

The real process seems much more complex, but anyway, integrating a differential equation leads to a set of possible results that can be noted

So the precision of these theories indicate the differences with the JPL ephemeris used as reference.

So the first thing to do is to find out the precision of JPL ephemeris.

I couldn't find directly the precision of DE200. I found an article,

The most important differences concern right ascensions. They reach

It would be more interesting to know the differences between DE200 and modern observations (like VLBI), but this leads to a question : why should we care about the precision given by VSOP87 (which is about few thousandth or hundredth of arc seconds between 1900 and 2100, cf VSOP page) if DE200 is much less precise?

DE406 is a compact and less precise version of DE405. From the presentation of DE405 by E.M Standish and an article

But the question arises for the FK5. In [Ber98], I found these informations about the FK5 :

Should I conclude that any position expressed in the FK5 can't be given with a precision better than 100 mas ( = 0.1 arc second) ?

TO DO

So I only based precision control on the precision given by the planetary theories. This mechanism will have to be changed to take into account the limitations.

When a computation is asked, the planetary theory classes check if the precision asked for a given julian day and body can be honoured. If not, this is memorized by a field of

`Body`

, containing a `jephem.astro.solarsystem.ComputationException`