@Bebs This is a test.

@TheDarkSide That's an interesting question.

I'd recommend asking it as a question on the site.

(Sorry I'm so late, by the way - this got lost in my inbox!)

@TheDarkSide I actually did something like this as an experiment in an Astronomy class. Note: old school. We were given a series of pictures of the moon, the times those pictures were taken, a formula for converting the size of the moon to a distance, and a precise length of the moon's orbit. We converted time to an angle and plotted the distance to scale. We hand drew the elipse of the orbit and then measured the orbital parameters (major axis, minor axis, etc).

It was fun and interesting.

@Donald.McLean Thanks, but there is no problem when the orbit is a plane.

It is an over-determined system.

We know the curve equation, and so we can fit: r and \theta

The problem is, when the plane changes.

You know about any orbit equation?

Unfortunately, I'm an astronomy newbie.

@HDE226868 Thanks for the encouragement.

(I'll have to rush out for a while)

@TheDarkSide Except for perturbations, orbits are elipses, and both the orbiting body and the orbited body are always in a plane together. Now if the orbited body is, itself, in orbit around an even larger body, then the planes of the two orbits will not coincide. They may be close, but it's pretty much impossible for them to be identical.

quora.com/…

@Donald.McLean I'm not even venturing into that complicated territory of e.g. Earth, Moon and Sun type of system.

All I'm saying is, let it be a problem of an orbiting body around a static massive body. The orbit shall be an ellipse.

We know how to deal with this problem.

All good until this point.

Now suppose, something forces the plane of the orbit to precess.

Do we know how to deal with this problem?

Perhaps yes at some level.

But do we know a general closed form solution for this precessing ellipse problem?

i.e. if we locate the coordinates at fixed times, can the general orbit, and hence, the complete Kepler problem, be completely determined.

I'm sure it is. Otherwise, observational astronomy wouldn't make sense.

I just need someone to point me towards a good reference for all of this.

@Donald.McLean Thanks for your interest in this problem, by the way.

:)

@TheDarkSide I try not to be a completely useless mod.