Is there anything special you have to keep in mind when dealing with large scale scenes, specifically those in outer space? I was experimenting with some last night and ran into some problems, specifically with the viewport camera, shadows (Shadow Bias had to be bumped up an order of a magnitude to get ray traced shadows to look OK), and rendering large volumes.

How do you compose a scene with very large objects in it, such as a planet? If you're not going to use simulations, then the actual numbers don't really matter do they? Or is it important to keep things in scale at all times?
If the latter is true, then leaving things at the default 1 unit = 1 meter is a bit of a problem correct? You end up with a sphere that's 6,000,000 meters/units in diameter (rough diameter of mars for example). And if you want to add some sort of hazy, volumetric like shape then that would also be very large, which then appears to take a *very* long time to render.

Are there any “tricks” to keep in mind when setting up a scene for stuff like this?

I'd keep your scene approximately the size of the viewport default construction plane if possible. Of course it can be a magnitude bigger or smaller, doesn't really matter unless you do some dynamics/rendering stuff where scale is quite important. It's just a good workflow habit not to change camera clipping planes, viewport settings etc. each time.
Also bare in mind you might run into some rounding errors (especially in SOPs ) if your model is FAR too big from the default Houdini scene.
Maybe someone from SESI can give you more precise numbers.

Hope that helps,
kuba

kuba
Also bare in mind you might run into some rounding errors (especially in SOPs ) if your model is FAR too big from the default Houdini scene.

Same thing if it is far too small. Sometimes I scale up the geometry, perform the sop, scale down again.
Also you might want to consider putting the object where “the action is at” at the origin. As in put your spaceship at the origin and your planet out in space. The further you are from the origin, the more rounding errors can occur when dealing with any kind of vector math.