If one is interested in widefield photography with a large imaging chip, it seems like a well corrected astrograph like an Epsilon 180ED at f/2.8 would out-perform a typical fast APO like a FSQ 106, from the perspective of f ratio. Most fast APO refractors do not get below f/4 or f/4.5. Are there any considerations I am missing out here? Thanks, Ivan
Widefield Scope Question
Started by ivanong, 12/24/2006 12:50PM
Posted 12/24/2006 12:50PM
Opening Post
Posted 12/24/2006 02:11PM
#1
Hi Ivan,
There are a few general considerations:
---The lower focal ratio scope will, of course, have a much smaller critical focus zone. Focusing with this scope needs to be precisely done, there's no room for error.
---Back focus will be less with the smaller f ratio. This will restrict what components you can hang on this scope.
---The central obstruction will reduce contrast somewhat.
---The image circle on the FSQ is twice as large.
A specific consideration to the Tak Epsilons would be concern that the focuser can take the weight of whatever you're going to hang on it. If I remember correctly, some of the Epsilons were a little weak in this regard.
A lot of people say that they have quite a bit of fun imaging with the Epsilon.
The next generation FSQ will be coming out shortly. Who knows how this will impact this comparison.
dan kowall
photonhunter.com
There are a few general considerations:
---The lower focal ratio scope will, of course, have a much smaller critical focus zone. Focusing with this scope needs to be precisely done, there's no room for error.
---Back focus will be less with the smaller f ratio. This will restrict what components you can hang on this scope.
---The central obstruction will reduce contrast somewhat.
---The image circle on the FSQ is twice as large.
A specific consideration to the Tak Epsilons would be concern that the focuser can take the weight of whatever you're going to hang on it. If I remember correctly, some of the Epsilons were a little weak in this regard.
A lot of people say that they have quite a bit of fun imaging with the Epsilon.
The next generation FSQ will be coming out shortly. Who knows how this will impact this comparison.
dan kowall
photonhunter.com
Funding Member
