Quote:
Originally Posted by Manav
1. This is parfocal with QHY9 not sure what that actually means?
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It means will this filter come to focus at the same point as the other filters in the wheel. The focus point can also be effected by the scope you are using , the spacing to the reducer/flattener, is it exists, as well as the other filters in the wheel and the F ratio of the scope.
I'd suggest it doesn't matter that much cos you need so much Ha data to reduce the noise you would normally focus with the Ha filter and then spend the lions share of the night shooting Ha anyway. And if you don't check focus while the temp is dropping, no matter what ever you're shooting, you're a mug.