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I now have the correct optical path length in my image train and I'm now getting the expected F/7.7 with the reducer. Note that the diagram I posted earlier in this thread, which was taken from the #94240 instruction sheet, is wrong according to Celestron support. It shows the back focus as being measured from the flange at the base of the reducer output threads. According to Celestron support the back focus is actually measured from the very right most part of the reducer. (Just as it is on the OTA when the reducer is not used.) That's a whopping 5/8" difference that makes all the difference in the world. I'm liking this reducer more and more every day.
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