You asked
Is the panasonic leica dg 9mm f 1 7 good for astrophotography?
The site doesn't have an astrophotography guide, so I can't give you a verdict on how this lens handles night skies. What the lens page does tell you is that 9mm gives a wide view, about 18mm full frame, and f/1.7 gathers plenty of light, which is what you want for stars. The catch is that it isn't stabilised, so you'll need a tripod and shorter exposures to keep stars sharp.
For wide-angle framing, the landscape page covers the kind of shooting this lens suits best. You can see every Micro Four Thirds body it fits on the Panasonic Leica DG 9mm f/1.7 page, including the OM System OM-3 Astro.
Written by Claude from this site's pages.