I think this can be done with some parenting and manipulation of the origin coordinates of the moons.

Lets start with a naming convention so my explaination makes sense:

The planet's name is: "Planet 1"
T the moon orbiting the planet is: "Moon 1"
The moon orbiting Moon 1 is: "Moon 2"

Setting up the animation:

I would take the Moon 2 and put its origin at the center of its orbit around Moon 1, which would probably also be the center of Moon 1. You can then animate the rotation to make Moon 2 orbit its parent (Moon 1).

Also, make Moon 1 the "parent" of Moon 2 ao that Moon 2 will follow Moon 1.

Now take the Moon 1 and put its origin at the center of its orbit around Planet 1, which would probably also be the center of Planet 1. You can then animate the rotation of Moon 1 to orbit its parent (Planet 1).

The result should be as follows:

• Moon 1 should rotate around its parent Planet 1, in a tidally locked orbit. Meaning Moon 1 will always face its parent (Planet 1) with the same side, but other then that it'll orbit its parent in a circular orbit.

• Moon 2, will follow its parent Moon 1, because Moon 1 has been defined as being its parent.

• Moon 2 should rotate around its parent Moon 1, in a tidally locked orbit. Meaning, Moon 2 will always face its parent (Moon 1) with the same side, but other then that it'll orbit its parent in a circular orbit.

**
**

Simulated axial rotation:

If you want the moons and planets to look like they rotate around their axis (instead of being tidally locked) you can animate their textures to reflect this.

 

Actual axial rotation:

Another option, if you need to rotate the moons around their axis without animating their texture. You could do the same as above, only you replace Moon 1 and Moon 2 with an intermediary object (lets call it a "null object").

This Null Object be anything, a sphere, a cube, doesnt matter as long as its an object and its made to be invisible during render time (hence the name "null object"). Then you animate the null object to orbit as if it were the moon (see my original example).

When the Null Object has its orbit, you turn the Null Object into the Moons' parent, so that the moons will follow the intermediary Null Object in its orbit.

Finally, now that the moons are following the Null Object, their origin point can be left unchanged at their center. Now, when you animate the rotation of the moons, they'll rotate around their axis, while following their null parents in orbit around their parent moon/planet.

The catch:

There is only one catch.. in older versions of bryce, using animation and parenting of objects used to be buggy, and sometimes it would break down entirely, messing up the animation quite horribly. I dont know if this has been fixed in bryce 6 or 7 because i never tried anything like this since bryce 5, but just in case it is still buggy, i recommend making a back-up of your un-animated scene before trying the above.

(_/)
(='.'=)
(")(")This is Bunny. Copy and paste bunny into your signature to help him gain world domination.