Why do focal reducers work like this???
Posted 18 January 2013 - 02:40 AM
When I adjust the distance between ccd and reducer to be closer to the correct distance, the same effect happens, but now the focus in the one corner is less out of focus, with the other corners still in focus. I am guessing, when I achieve the correct distance between ccd and reducer, all four corners will be in focus.
My question is therefore simpel: shouldnt all 4 corners come closer to being corrected and in focus together? Why is one corner different from the others?
I just want to add that I think my collimation and offset is pretty spot on, so this shouldnt be causing the effect.
Posted 18 January 2013 - 08:51 AM
Posted 18 January 2013 - 02:06 PM
How is your camera attached? Threaded or compression? Is there a way to shim near that corner to see if it gets better/worse?
How have you collimated?
Do you have CCD Inspector?
Posted 19 January 2013 - 10:21 AM
I used ccd inspector, but my license expired a while ago.
What goes for collimation, I really think my scope is collimated well. I calculated my exact offset and collimated with an holographic attachment and howie glatter tools.
A question that I was wondering to ask, should one collimate then with or without the offset of the secondary?
I know this might seem like a stupid question, but I am getting out of ideas on what to do.
Posted 21 January 2013 - 12:47 AM
f/2.8 is horrifically unforgiving. Maybe grab a Paracorr and try f/4.6?
Posted 21 January 2013 - 04:59 AM
More specifically with the CCD alignment - perhaps As quoted fast optical systems are very sensitive to alignment problems :o I run my 12" f/10 SCT @ f/3.6 + tiny CCD and understand your concerns
I guess that might be because something is not perfectly perpendicular to the optical axis.