Canon 70-200mm in SGPro

Does anyone know if I was to use my canon 70-200mm 2.8L in Sgrpo for plate solving and imaging lens… do I have to make a new profile for each focal length??? Thanks everyone

I would say you definitely need to. SGP has to pass on to the plate solver the pixel size in arc seconds and this is worked out from your focal length.

Thank you very much for the info

Yup, I would also say so, Also, to be honest, the zooms are pretty lousy lenses for astronomy. I have the newest version of the 70-200 as well as the fixed 135 f2 and the fixed 200 mm f2.8. I am using them with an STT 8300 at home and a QSI 6120 at a remote site.

Both fixed focus lenses are way better in terms of star and image quality than the zoom, despite the zoom being way more expensive. After trying several of my high quality zooms, I would never use them for astronomy again. A good choice is apparently also the Rokinon 135, widely used by many and cheaper than the Canon.

The other thing I would do is to stop these down to no less than f4.5. Trying to run them wide open will always give you crappy stars in the corners. The issue with stopping them down is that you will get 6-8 diffraction spikes on bright stars due to the blades on the iris stop. The best way to deal with both is to buy an aluminum screw-on lens cap (about $10 on eBay) and drill the proper sized aperture in the center for whatever f ratio you choose.

Results speak for themselves:

200 mm STT


Awesome thanks CCDman I will give that a try! :+1:t2: