Reducer/Flattener Backfocus

[dave_galera]

I have a C8 SCT with a Meade 4000 series 0.63 reducer/flattener and I am trying to determine the correct distance from the reducer/flattener to my cameras sensor, i.e. the backfocus.

I have searched the web and only a couple of articles seem to indicate that this dimension is 105mm, but know where can I find a definitive answer.

Can anybody point me in the right direction, thanks in advance.

[Merlin66]

The MAPUG site has lot's of details to confirm the 105/110mm back focus

[dave_galera]

Thanks for pointer I will look it up.

[ollypenrice]

It is quite a tolerant reducer, unlike some. What happens is that your true F ratio is affected. Plate solving may not give F6.3.

Olly