Is the leica super apo summicron sl 21mm f 2 asph good for astrophotography?

Here is what the site says about that.

From Leica Super-APO-Summicron-SL 21mm f/2 ASPH: Leica Super-APO-Summicron-SL 21mm f/2 ASPH: A prime lens by Leica for Full frame cameras, 21mm f/2. Specs - Maker: Leica - Focal length: 21mm (prime) - Maximum aperture: f/2 - Made for: Full frame sensors - Mounts: L-Mount - Stabilised: no - Autofocus: yes What it frames like - On full frame (L-Mount): as marked, 21mm. - On APS-C (L-Mount): like 32mm on full frame; f/2 gives about the depth of field of f/3 there. ...

From Focal length converter: Aperture and depth of field: The f-number sets exposure, and that doesn't change with sensor size: f/2.8 gives the same brightness on a phone as on medium format. Depth of field does change. At the same framing, multiply the f-number by the crop factor to get the full-frame aperture with the same depth of field: f/1.8 on APS-C gives about the background blur of f/2.7 on full frame, and f/1.8 on Micro Four Thirds about ...

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