Stellarium

ephemeris accuracy

Asked by Ash Ghala

Greetings:

The current Swiss Ephemeris (astro.com or www.astro.com/swisseph/swephinfo_e.htm) "...is based on the DE431 ephemeris released by JPL in September 2013..." showed the Moon's North Node ecliptic longitude last Wednesday (when Moon crossed the ecliptic) at around 161 degrees, but according to Stellarium 0.15.0 it was around 165 degrees!! Moreover, the position of Moon at noon in Southern California on Oct. 30, 2016 was different by about 16 minutes of arc (or roughly half an hour of clock time). Which source is more accurate? Could you please enlighten me? Thank you so much in advance for your help. Have a great week.

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gzotti
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Best gzotti (georg-zotti) said : 		#1

The tooltip in the DE43x section of the config panel which is labeled "experimental" informs you that this feature is not yet completely tested out. Indeed there are some issues in V0.15 related to DE43x which require corrections. Currently (0.15), do not rely on DE43x results displayed in Stellarium. This should mostly affect historical questions.
The lunar position difference for the present time however may be related to geocentric vs. topocentric position, a.k.a. parallax shift.

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Ash Ghala (ashghala) said : 		#2

Thanks gzotti, that solved my question.