[Outcast (Carlton)]

Andy,

Bintel's site states 'Back focus is 80mm +/- 2mm from Corrector Lens to image plane'.

In this I would read this as 80mm between your coma corrector lens to the sensor.

You should be able to find sensor depth for your camera, add in the T2 adapter thickness & then make up the remainder to 80mm with spacers.

From talking with more experienced imagers on this forum, I believe most DSLR's are around 50 - 55mm sensor depth including T2 adapter. This indeed proved quite correct when I was looking at achieving back focus of 105mm when using an f6.3 focal reducer on an SCT.

Thus, I would suggest you are looking at 50 - 55mm for your camera & looking for 30 - 25mm distance to your corrector lens to achieve the 80mm back focus recommended by Bintel (assuming there number is correct).

You may then need to do some minor tweaking of exact spacing because, none of that information above allows for threads, shoulders on corrector in relation to where the corrector lens is, etc...

However, this should give you a pretty good place to start.

Hopefully, someone with way more experience will jump in soon & either shoot me down or back me up... I don't mind; just thought I'd jump in with what little knowledge I have to see if I could help..

Cheers