woodblock Posted April 1, 2022 Share Posted April 1, 2022 I have a SW 200PDS and I bought it with a matching SW Coma Corrector lens. I've been using it with my DSLR for ages and the setup works well. But I'm now looking at changing to a CMOS camera still using the coma corrector and the coma corrector back focus distance has come into 'focus'. When I started with it I didn't even think about it I just connected it all up and it worked. I tried without the coma corrector and I could see straight away that the coma corrector is doing it's job. The back focus distance is given as 55mm. So I have a few questions about this Back Focus distance. 1. When measuring the distance do you measure from the rear surface of the coma corrector lens to the sensor? 2. How critical is this distance? 3. What happens if the distance is wrong? Was I just very lucky that when I connected it all up the distance was correct? Cheers Steve Quote Link to comment Share on other sites More sharing options...
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