Quote:
Originally Posted by SimmoW
Yes this is a really useful thread, dare I say 'award winning! 😁
I've heard from one technical expert how bad Orion Optics can be, having to recoat a new expensive mirror! And another industry supplier saying pretty disappointing things about their tactics. Just rumour of course, but enough for me to be glad I've never used them.
At these longer focal lengths, once off focusing at start is not possible. Temp changes cause the focus point to vary too much
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My CDK17 has a carbon fibre truss. Once the mirrors have equalised in temperature its focus does not shift hardly at all. In fact the next night it will still be almost exactly in focus much like RCOS used to promote with their scopes. Still in focus the next night.
So focus shift may be true of some scopes but not the CDK or RCOS in my experience. I still check and refocus after a substantial temp shift and I can get a slight improvement but its a small gain. An FSQ shifts the most of any scope I have used. The AP Honders shifts a bit as well but not that much and it seems to be fairly predictable and temp compensation of Sky X seems to keep up with it.
Greg.