|
Looking at the difference in thermal expansion, even if you have two dirty big dove tails top and bottom, you will see the expansion. Even at 1200mm my skywatcher expands in what terms i cannot tell you exactly but it brings my fwhm from say 2.5 up to 3.5 over the span of a hour and a half, now i can tell you that is a big difference in clarity.
CF tubes are generally a lot lighter even with the epoxy resin and differential materials.
Good imaging practice you should be assessing your focus every hour or so, now with auto focusing this is very easy to do, you don't even have to slew off to a different part of the sky. Though everybody has their own way at the end of the night.
Good luck with the 12" gso RC.
|