You asked
Is the nikon z 20mm f 1 8 s good for astrophotography?
The Nikon Z 20mm f/1.8 S is a good starting point for night skies. It's a fast, wide prime, and the site describes it as popular for landscapes and night skies. The f/1.8 aperture lets in plenty of light, and 20mm takes in a big stretch of sky.
It isn't stabilised, so you'll want a tripod for longer exposures. On a full-frame body it frames as a true 20mm. Full-frame bodies such as the Nikon Z6 II and Nikon Z7 II both take it. If you're shooting landscapes too, the landscape guide covers how wide lenses fit into that work.
Written by Claude from this site's pages.