|
Parfocal is a vague term. I have a set of "parfocal" Astrodon LRGB filters. They all focus at slightly different distances and on my Tak FSQ-106ED at f/5 they are not parfocal. The maximum difference in focal distance is between red and blue at just under 90 microns compared to a CFZ of 55 microns. On my GSO RC10 at f/8 (with a much more generous CFZ of 140 microns) they are fine.
So, YMMV, especially with faster scopes.
Cheers,
Rick.
|