ccwoodruff Posted November 28, 2023 Report Share Posted November 28, 2023 Hello, I have a 12.5" f4.1 (1300mm) Native Newt that I am trying to setup my 8 year old ASA 2" .73 reducer corrector so it becomes a 12.5" f3 (950mm). It will be used with a QHY268m camera who's diagonal measures 28.3 mm. I believe that the right back focus is 65.5mm but I wanted to be sure and also see if there are any variances to get the best image quality. Thanks in advance! Chris Link to comment Share on other sites More sharing options...
photon Posted December 3, 2023 Report Share Posted December 3, 2023 (edited) Hi Chris, your backfocus with ~65.5mm seems to be right, see attached file (page 1) for some examples. You might need to increase the calculated backfocus by 1/3 of your filter thickness. -- Gerald newCorr_2Zoll_Reducer.pdf Edited December 3, 2023 by photon Link to comment Share on other sites More sharing options...
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