Hi, > As far as I know, also the VSOP87 has a temporal limitation and was > derived to provide good results for about the years -4000...+8000. But I > don't know the exact behaviour, i.e. how fast it diverges from nature > beyond that range. Or can you please define "almost no limit"?
"Almost no limit" in the sense that the accuracy of the trigonometric series (which define the elements of the theory) is timeless (e.g. truncature at 10.e-15 for the best accuracy). So you can compute the position of a planet at any epoch. But if you want to compare that position to the actual position of the planet ... it's an issue. From a strict scientifical point of view, it is impossible, because we don't have direct measurements to compare to the elements of the theory (e.g. a direct measure of the Earth-Sun distance doesn't exist). That means that the comparaison must be done on derived measurements, which have themselves errors. The VSOP theory can be used on the period -10000 ... +10000 with the lowest level of uncertainty one can expect to have. For this time span, there's also the numerical solution named INPOP (http://www.imcce.fr/inpop/), which is handled by the Calceph library (http://www.imcce.fr/inpop/calceph/index.php) (which handle also JPL's DExxx solutions), as well JPL's solutions. Both VSOP and INPOP provide ephemeris of planets with respect to the ICRF. For ephemeris calculation on a larger period of time (tens of thousand to millions of years), it exists dedicated planetary theory such as TOP82 (and newest version), usually limited to the motion of the 4 main planets (http://adsabs.harvard.edu/full/1983A%26A...120..197S). cheers, jerome -- --- Dr. Jerome Berthier ------------------ Phone: +33 (0)14051 2261 -- Institut de mecanique celeste Fax: +33 (0)14633 2834 -- 77 av. Denfert Rochereau Mailto:[email protected] -- --- 75014 Paris - France --------------------- http://www.imcce.fr/ -- ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Stellarium-pubdevel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/stellarium-pubdevel
