Quote:
Originally Posted by PRejto
Well, I have removed my original post! Thanks to Ray's comment I made an elementary mistake so there is no point in leaving this up at all. In my rush to avoid getting dust into my filter wheel I didn't check carefully enough what was put in which slot.
Sadly, I'm back to wondering if there is something not quite right about my TEC180 lens? I'm getting a shift of ca 200+ microns going from the Red focal point to the Blue focal point. It shouldn't be more than around 60 microns.
Peter
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I know this is an old post but people read old posts when searching and I don't want to leave up any bad information.
After much experimentation I can safely say that the cause of my R/B focus offsets was due to the flattener (and not the flattener position). With the flattener installed - using 3 cameras and 3 different sets of filters - testing all showed this large offset with the flattener and all showed essentially no focus shift with the flattener removed. The flattener position was vetted by 3 experienced people as dead on but nevertheless I experimented with positions up to 3 mm in either direction with no change observed in the focus offset. I then installed a TAK flattener and checked it at a range of positions with no focus offset in any position. Case closed!