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CST back focus question
Greetings,
I have used a refractor for some time and just bought a Celestron EdgeHD 9.25. Back focus on the refractor was absolutely critical. I expect to have a problem getting exactly the right back focus with the CST and mentioned that to a vendor. He said that back focus with something like the EdgeHD series is not as critical as with a refractor. I might be out by two mm with my current equipment and he said, it would not really impact the edges compared to the refractor.
Is that true? If so, can someone explain in layman's terms why it would be so.
Regards
Stephen
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