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The Celestron Reducer backfocus debate
I’m in the process of re-purposing an older Celestron C11 SCT. One part of that is the addition of a Celestron F6.3 reducer. But I find Celestron have not been forthcoming with any info on the optimal backfocus requirement of this item.
The Description on Bintel’s site claims a 24mm image circle and 85mm backfocus. And yet, a bit of scouring Cloudy Nights and the like more often than not comes up with a figure of 105mm.
Some of the discussions claim that at 105mm, there is serious distortion of stars on the outer making OAGs unworkable.
I gather this has nothing to do with the ccd/camera being used but is entirely a function of the reducer.
Has anyone come up with anything definitive on this question. Celestron themselves offer no assistance.
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