big asteroid mounted on an empty cmp w/ hardpoints rotating around the center of the orbit + scaled up 'badlands' asteroid-trails equipped as effects on it. doable, but the end results may not be what you want - also there's the gravity well effect, which lags like crazy on my cards anyhoo - but it does look like a comets head. well there's my idea =)

Another way to get them up and running is to create a base with no mat file so its invisible. Set a patrol path between them and the comet will go from one end of a system to the other. You would need to define a comet faction just for this btw. Define the comet in shiparch so it can only travel in one direction, not side to side. I use an asteroid with an HpFX hardpoint to make the tail, defined seperatley of course and an engine to get it moving and there it is. Means you can blow it up as well, assuming you can catch it of course lol

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