Like others I am intrigued about the possibility of the Q 5. Obviously thankful for the military reasons for potential production as pointed out by a couple of gentlemen in another thread!!
I own a Q 3.5 fieldscope which has broadband coatings and have a good feel for what this 1/3 obstructed optically excellent wee scope can deliver. Crunching numbers tells me it has a similar light collection ability of a top notch 83 mm refractor (assuming BB coatings are 97% efficient) and allowing for the CO. I note my Q3.5 seems to perform a fair bit worse than a 80 mm refractor on low contrast planetary perhaps similar to a top notch 60 mm refractor. I am using the assumption that a good approximation is that the aperture minus the central obstruction. 89-29 for a Q 3.5.
I do not own a top notch 60 mm refractor currently.
Running similar comparisons for a Q5 I calculate the Q 5 should perform similarly on light collection to a 118 mm refractor for light collection and about 85 mm for low contrast performance.
Similarly one can extend this to the Q 7 and we get a light collection similar to a top notch 165 mm refractor and about 119 mm for low contrast performance.
I have a quality IM 703 which is 180 mm and 1/3 obstructed, I suspect these numbers are quite good approximations.
The aesthetic qualities and portability etc of the Q scopes are not considered here.
I am assuming the refractors have very close to 100% light throughput.
Your thoughts on this would be appreciated.