Talk:Nodal precession

" If the orbit is retrograde the increases and the longitude of the ascending node decreases."

should have been: If the orbit is retrograde, this increases the longitude of the ascending node i.e. node precesses eastward.

J2 Formula

Does anyone have a citation/source for the given J2 formula? I've always seen J2 derived as part of a harmonic expansion of measured gravity and not as an analytic formula. — Preceding unsigned comment added by Spaceman13 (talk • contribs) 15:16, 30 April 2018 (UTC)

précession apparente d'un satellite à 56° prograde et 800km altitude

Une maquette présentant les angles d'ascension droite de l'équateur céleste me fait comprendre que si la précession nodale calculée est de -3.68°, ET que le soleil présente un gain de 0.98° par jour, la somme qui représente la précession apparente est une addition qui atteint 4.66° par jour. Ardéjé85 (talk) 16:14, 14 August 2020 (UTC)

Appearance of nodal precession with respect to the Sun

I think the result given in the article is incorrect. While it is correct that the Sun appears to move +1° (eastward) in the sky per day, and the orbit of the satellite in the example precesses -3.7° (westward), the "apparent motion of the sun relative to the orbit plane" should be the difference of these two: (-3.67)-(+1)=-4.7 degrees per day (westward), resulting in an apparent realignment cycle of approximately 77 days. As a qualitative sanity check, one can use the example of a sun-synchronous orbit in which the satellite's inclination is chosen >90° to obtain a nodal precession of +1° (eastward) to match that of the Sun. Here, the math is clearly, again, the difference of the two precessions (+1-(+1)=0), so no apparent motion. (Ahh, after google translating the comment of Ardéje (above, 14 August 2020), I see that s/he has called out the same mistake.)ScriboErgoSum (talk) 17:57, 19 May 2025 (UTC)