NGC6888 - Crescent Nebula

ENHANCE! I decided to revisit the Crescent before it fell from view this year with my new scope. I figured a nice test comparison of the resolving power of the scope would be fun to see against the widefield Redcat. I’m overall happy with the result, but the guiding woes continue. Finally, after 5 nights, I gathered enough data to make processing it worthwhile. Each night, I set the scope to take 60, 3-minute subframes of the Crescent before it fell too low in the sky, which should total about 15 hours worth of integration time… I tossed out almost half of the 15h of subframes due to streaky stars, egg-shaped stars, and the target occasionally drifting out of the center of the FOV for about 5-10 frames. Last night, I watched guiding for a good hour before I decided to just let it run, and was getting about .5-.6” total RMS… those 20 or so frames came out fine, but later in the night (as has been the case every night with the new scope), something changes. This to me screams “guiding problems,” and no matter how I tinker, I don’t seem to be making any improvements. On two of the nights I imaged, winds were calm throughout the night, and I tossed out just as many subframes as I did on the 3 nights where there was a breeze, so I feel safe concluding that the wind isn’t the culprit. I’ve now tweaked the guiding calibration settings to ensure they’re in line with the recommended settings. I’ve tried recalibrating every night and after meridian flip and letting calibration auto-restore. I’ve ensured good focus and the focal length are correct. I’ve tried exposure times anywhere from .5 sec to 3 seconds to eliminate the effects of seeing. I’ve tried lower and higher gain settings on the camera. I’ve tried higher and lower aggression settings on the ASIAIR. I’ve tried with and without dithering. I’ve adjusted the guiding settling settings on the ASIAIR. Nothing has made a noticeable impact on the amount of subframes I have to toss every morning. I’m going to try swapping out the guide scope to my old guide scope to see if that helps, though I’m a little nervous guiding 925mm focal length with a 120mm guide scope, but at this point, it doesn’t appear I have another choice but to try! If that isn’t effective, I may try an OAG. If that isn’t effective, I may need to inspect/clean/tune the mount. We’ll see!