Quote:
Originally Posted by Stefan Buda
Yes, I would expect the scope to be in focus for the orientation where focus was achieved even if you moved away temporarily from that position. The question is whether the scope was still focused in the other orientation where the Bahtinov indicated that it was not.
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Ah, got you. I understand.
Well, on the first night I focused with the mask (on Rigil kent) then slewed to my target, this worked with Ha and Oiii but not Sii. Focus was fine for the first two filters, despite the differing orientation. The 2nd night I had issues with all of them.
Next opportunity I will try HFD focusing near Rigil (or another bright star) then pop the mask on and see if it agrees.