View Single Post
Old 20-10-2013, 11:49 AM
RickS's Avatar
RickS (Rick)
PI cult recruiter

RickS is offline
Join Date: Apr 2010
Location: Brisbane
Posts: 10,584

One good way to find out your true focal length is with plate solving. The focal length specs for most scopes are a rough approximation.

The effects of an AO or filters should be negligible (these should be designed to have zero power) but flatteners, reducers and barlows will certainly have a significant effect.

You'll find a formula for the CFZ and a calculator here:

The CFZ is dependent on wavelength (which is why CCDAP gives you different values).

Reply With Quote