Hi Graz,
The exchange rate going down the chute saw me shell out close to $1500, plus the UV/IR filter. Am I disappointed? No way! I now have an excellent H alpha scope for really very little when compared to dedicated H alpha scopes, and to the aperture I want.
The Quark has a built in 4.2X barlow within it. So it is better suited to faster focal ratio refractors. The Daystar info says best between f/5 and f/9. Otherwise the resulting magnification is just too much. A 25mm plossl is really all I need here, giving me 84X with this scope & Quark combination. Image quality quickly drops during the day if pushing magnification too far.
An 80mm f/11 refractor may be a bit long. But, I don't know for sure,
Another thing too is the whole disk being visible at once is limited to scopes with a focal length less than 450mm (
Daystar suggestion), or 500mm with a focal reducer in the eyepiece in a 500mm scope (
my direct observations). The small field stop in the filter is the reason for this. Here using a 68deg, 82deg, 100deg or even 120deg eyepiece won't be of use. You just won't fill the AFOV. Even Daystar suggests sticking with long focal length plossl eyepieces. If you do use a focal reducer, DO NOT place it in the barrel of the Quark! This point in the optical train does see heat, and enough to stuff the coatings - Steve Massey has experience with this!!! Place the focal reducer in the barrel of the eyepiece only.
The UV/IR filter, yes it is just a standard UV/IR filter, and yes, it always sits in front of a 2" diagonal. I would steer away from a 1.25" diagonal as this puts the diagonal, and so the filter, closer to the focal point of the lens.