You asked
Is the laowa 4mm f 2 8 fisheye mft good for astrophotography?
I don't have a guide on astrophotography, so I can't tell you how this lens handles the night sky. Here's what the Laowa page does say: it's a 4mm f/2.8 fisheye for Micro Four Thirds, so it frames like 8mm on full frame. It's manual focus and not stabilised. Manual focus is workable for stars, but you'll need to set focus by hand on a distant point of light. The wide f/2.8 aperture gathers plenty of light, which helps in dim conditions. The Lenses guide explains why that matters. The page also lists the OM System OM-3 Astro among the bodies it fits, but I haven't covered how that pairing performs for astro work, so check the camera's own page before you buy.
Written by Claude from this site's pages.