LEGO baseplates doing good work so far.

The ruling is - if your ships baseplates is overlapped by the asteroid itself (birds eye view to judge), roll your obstacle collision die. Crits and hits apply.

Made them large to promote flying and navigation, etc.

What happens when your ship is sitting on an asteroid?

Edit:

Nevermind, lego base would let you pull them off...

We have a couple rules for ships that will end their movement ON an asteroid. Either backtrack the maneuver, roll the collision die or, if it's a game where we're working on navigation, the ship is destroyed. Also, if you back track and roll the collision die you're most likely going to roll another trying to get away from the asteroid on the next turn. It makes it very penalizing to miss a maneuver and hit one of these. It's all for fun though. And the LEGO bases do add some more flexibility.