My larger MDF bases have now turned up, so I've tried my hand at a planet template for the Earth. At just under 13“ in diameter, it's pretty big, even compared to the NAC Heavy Carrier shown here. It's just about small enough to fit on a standard gaming table though, and plenty small enough for larger tables to allow the full gravity well (which stretches another 16” beyond the surface (i.e., radius) of the Earth). I also have a base which is 13cm in diameter, which could be used when playing using centimetres as movement units.

Next up though is probably the Mars template (7“ diameter, with only 8” of gravity well).

My rules on planets list the size of template needed (and size of gravity wells) for all the planets in solar system.