Celestia Forums

Also, I would like to be able to follow an object as such:

1. Select the object
2. At the time of the selection you are at distance D from the centers of the foci or one of the foci of the orbit.
3. Move along with the object on a smaller or larger elipse than the ortbit elipse of the body.

For instance, if we had two earths, on concentric orbits and moving at the same speed (impossible, I know), you would track the first from the second.

Aphex wrote:Also, I would like to be able to follow an object as such:

1. Select the object
2. At the time of the selection you are at distance D from the centers of the foci or one of the foci of the orbit.
3. Move along with the object on a smaller or larger elipse than the ortbit elipse of the body.

For instance, if we had two earths, on concentric orbits and moving at the same speed (impossible, I know), you would track the first from the second.

It's a little unclear to me what you want. I think if you had two earths, on concentric orbits and moving at the same speed (impossible, as you know), their orbital periods would be different (since the outer orbit is larger than the inner one, moving at the same speed the outer earth would take longer to complete its orbit than the inner one), so they would move apart as the outer earth falls progressively behind the inner one. I'm guessing that's not what you want.

Possibly what you want is for the observer to remain at a fixed distance from the target, lying along the line connecting the target with the focus of its orbit? Or is it something else? Perhaps you could explain why you want to do this.

- Hank

Same speed I mean same angular velocity

The observed body moves in it's orbit. The observer moves along with the body, but on a smaller or wider orbit, so that there is always a straight line between one focus (or the center), the observer and the observed.

Okay, I think you can do that now, provided there is an object at the focus of the observed body's orbit (which gravity normally requires). First, select the observed body, press 'f' to follow it, then press 'c' to center it , then select the object at the focus, press ':' to lock phase with the focus object, then press shift+'c' to center it behind the observed body. Does that do what you want?

- Hank

Yes, that pretty much does it. But would it be possible to point/lock the camera to a point in space where there is no object?

Another interesting feature would be to allow objects trace their movements on the stellar background. For instance, I am on Earth, following it and want to trace the movements of planet Mars on the night sky over one year.