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Hi Dunk,
Firstly, I decided to get a clip in CLS filter for my Sony. Saves any hassles with back focus settings. I can't see the point of other specialised filters for an unmodded colour camera but see below
Secondly, my back focus is a mess. Last night I ventured out into my back yard in the moonlight with lots of smoke and some wind to test the 55 mm back focus with my setup. I tried to focus on a star with a Bahtinov mask and I couldn't do it as it was always out of focus.
I extended the Flat 61A from 0.5 mm back to 11.7 mm (for Sony?) and was able to focus on the star. I then did a couple of quick shots of the Orion Nebula and it was not in focus. Crappy conditions made me call it a night. The forecast looks dismal for the next few nights so I have to wait and see. I will have another go at taking a few subs of the Orion Nebula with the 0.5 mm setting on my Flat 61A and see what happens. I am concerned about not being able to focus properly without the 11.7 mm setting on the Flat 61A.
In the mean time, I am trying to stop myself from buying a ZWO ASI 1600GT. I have to stop my drooling or my wife will think I am getting old timers disease and put me in a nursing home. I will still need to get back focus even if I do get the 1600GT.
That link you sent makes a lot more sense about how to install a filter inside the Flat 61A housing. Thanks for that. I misread it and thought it went on the camera end of the housing.
You would think this would be easy wouldn't you?
Cheers
Stephen
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