You asked

Is the panasonic lumix g x 12 35mm f 2 8 ii good for astrophotography?

Here is what the site says about that.

From Panasonic Lumix G X 12-35mm f/2.8 II: Panasonic Lumix G X 12-35mm f/2.8 II: A zoom lens by Panasonic for Micro Four Thirds cameras, 12-35mm f/2.8. Specs - Maker: Panasonic - Focal length: 12-35mm (zoom) - Maximum aperture: f/2.8 - Made for: Micro Four Thirds sensors - Mounts: Micro Four Thirds - Stabilised: yes - Autofocus: yes What it frames like - On Micro Four Thirds (Micro Four Thirds): like 24-70mm on full frame; f/2.8 gives about the depth of field of f/5.6 there. ...

From Panasonic Lumix G X 35-100mm f/2.8 II: Panasonic Lumix G X 35-100mm f/2.8 II: A zoom lens by Panasonic for Micro Four Thirds cameras, 35-100mm f/2.8.

Quoted from this site's pages.

From these pages