ZWO ASI533 MC Pro Back Spacing

sitt

I'm new to astrophotography and a little confused on back spacing on the ZWO ASI533 MC Pro.

I have a Celestron CPC 9.25 Edge HD and according to Celestron the back spacing should be 146mm but ZWO state back spacing should be 55mm https://astronomy-imaging-camera.com/product/asi533mc-pro-color

Which is correct?

katherine.tsai

You need to follow the back focus provided by the telescope manufacture, we provide 55mm back focus because it is suitable for most of the optics.

sitt

Great thank you

Chiefsmith

I am having an issue with back spacing using the ZWO adapter for lenses with the Sony EF-mount on the ASI533MC Pro. I am not able to come close to focusing using the Samyang 21mm f/1.4 lens. This lens will barely reach infinity focus on either of my Sony cameras. Is this an issue with a bad lens (I just bought it two weeks ago and tonight was the first night with a clear enough sky to try it on the 533) or just something with Samyang lenses?