Quote:
Originally Posted by gregbradley
Reducers on RCs are likely to be problematic. I have a .66X reducer for my CDK17. It works great and corrects even the 16803 field of view but it has a tiny ideal metal back distance of 54mm. ZWO cameras and filter wheel and off axis guiders work on a 55mm backfocus requirement so that would be OK.
But my current setup meant I was too far off and I needed to use a guide scope.
It would work well sometimes and sometimes I would get some eggy stars. Not really bad but eggy stars are an image wrecker.
I have a large Riccardi reducer. I may try to rig it up to fit the CDK and see what happens.
I used to use a Tak FS102 F6 reducer on my 12 inch RC I had once.
It corrected the stars mostly but the corners were still not very good.
I later had a 4 inch Tak reducer, that may have worked but it would be experimental. I would predict it would be OK for an APSc sensor but a full frame one would have weak to bad corners.
Full frame sensors are quite demanding things.
Putting a reducer on an RC is probably not a good idea. Also you get the larger RC to get the extra aperture and the longer focal length. I don't know how much it speeds up exposures. Less than you may thing. Aperture is the thing that controls the light going in. Reducers just focus that light more tightly so that some of the light that misses the sensor is now hits the sensor. You get a wider field of view. I don't see that objects within that field of view get anymore light so exposure time will be the same.
Greg.
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Thank you Greg reading you experiences has been a great help.
The focal length of the 16 and even the 12 had me worried and I saw the fix as a reducer which seems not a good idea at all.
As I just now mentioned to Paul I am going to back off, learn more and try and work out my motivations and just what I want to do.
Thanks you have really helped me.
Alex