I currently have on loan an older C11 XLT. I was pretty excited about trying it out for my EAA and planetary imaging endeavors as it's a big upgrade on the C8 I've been using for the last year. Unfortunately it is not performing as well as I'd hoped and I'm trying to figure out if I'm doing something wrong or if there is an issue with the optics.. I'm a relative newbie but I'm comfortable with collimation basics and have used metaguide to get my C8 dialed in quite nicely.
Two things jump out as a little weird to me, hopefully someone can steer me straight here or give some general troubleshooting pointers.
Firstly - I can get the collimation close to good but found that one of the adjustment screws is fully snug while the other 2 are quite loose. I don't remember getting into that situation with the C8. It doesn't feel right and I can't fine tune the collimation. Should I "hit reset" and loosen all 3 and start over?
Second - even with the collimation close to good I can't get any distinct diffraction rings either side of focus. The are portions of rings in places, example attached. Tube had been outside for hours, no sign of thermal currents. Seeing was quite good and I tested on a few stars close to zenith. The Bahtinov pattern was also somewhat indistinct, not nearly as well defined as I see on the C8.
Thanks in advance.