baader coma corrector III spacing for dslrs

recommendations and thoughts

Not the best cc we've tried by a long way. If you've not yet committed, go elsewhere. There are far better to be had. 

Firstly -and especially for f4.7 or faster- lose the tilt and vignette inducing Baader supplied m42 adaptor and get a properly machined 11mm optical path m48-eos t ring (~9mm for Nikon). To get anywhere near decently corrected, non-astigmatic stars edge to edge over aps-c, you'll need at least 58mm spacing between the shoulder of the cc to the camera sensor.

The following combination worked for our eos700 using a filter ring, minus the glass, for the 4mm spacer:

focuser - cc - 4mm spacer - m48 t ring - camera

If however you're serious about this, get the 4 element gpu cc.

Failing/cant's afford that, the sw 0.9 or the gso 1.1. 

Nice comparison here.

Baader's diagram