nakbrooks Posted September 7, 2016 Report Share Posted September 7, 2016 Is anyone else on the forum operating the 400mm Cassegrain (or 500C/600C - they are much the same) with the 4" corrector? I have a small problem I would like some help with if possible. Thanks. Link to comment Share on other sites More sharing options...
lukepower Posted September 7, 2016 Report Share Posted September 7, 2016 Nigel, well, I have my 20" which also uses the 4" reducer/corrector (I have the corrector here as a spare part but never used it). The tube wasn't made by ASA; though Link to comment Share on other sites More sharing options...
nakbrooks Posted September 7, 2016 Author Report Share Posted September 7, 2016 Thanks Luke. I'm trying to find someone with the same OTA configuration as me (400C, ASA rotator, 4" corrector) so I can work through some back-focus problems. I will post more details a bit later. Link to comment Share on other sites More sharing options...
lukepower Posted September 7, 2016 Report Share Posted September 7, 2016 Back focus was a pain in the ass for me, a bit due to the tight requirements of the ASA correctors, and even more due to the mechanical construction of my OTA combined with the optics (which were, surprise, a little below the projected f/3 and thus the backfocus was lower than expected). Link to comment Share on other sites More sharing options...
nakbrooks Posted September 7, 2016 Author Report Share Posted September 7, 2016 I've moved this to the Correctors section as it is more relevant there. Link to comment Share on other sites More sharing options...
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