Demon Posted June 21, 2022 Share Posted June 21, 2022 I get backfocus distance to camera, however this question is really about the other side and more so in relation to the secondary and focuser being where it needs to go??? Also I appreciate imaging newts have larger secondary mirrors for the larger chip size compared to pupil size outside the focuser. So where do the field flateners need to go in relation to the secondary and focuser? If a camera is positioned at the correct distance from the secondary without a field flattener, then if a field flattener (with no affect on focal ratio) is added, firstly would the camera stay in the same place in relation to secondary? If a field flattened requiring 55mm backfocus was required it would need to go 55mm in front of camera, so would you need a secondary and focuser that allows the camera to be more than 55mm past the focuser? Or is it possible with some focusers to mount field flattener on the secondary side of the focuser? I appreciate other aspects including filter wheel etc but not getting into that yet as just want to understand first please. I need to get a new secondary and want to make sure it's big enough but small as possible to take a flattener and all works with focuser. I couldn't find what I was after searching, so would appreciate your expertise, hope this makes sense, thanks. Quote Link to comment Share on other sites More sharing options...
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