I picked up a used AT92 (third owner), as I've been searching for something fast-ish with good optics and APS-C coverage for widefield. I've been disappointed with a few recent purchases, but think I landed a keeper on this one. When I first got the scope I checked the focuser alignment with a laser and it was off by a few mm from hitting the center of the objective. After fixing that alignment, the lens cell then needed to be aligned to the new focuser angle. I did this with the Takahashi collimating scope. To my pleasant surprise the first frames that came off the chip were really good. I didn't have to fuss with tilt or anything at all. I did see some dark spikes that suggested the radial lens grub screws were too tight, but it was also very very cold outside. I did very slightly loosen the grubs for a subsequent session and that seemed to do the trick. I don't see any dark spikes anymore.

The flattener works really, really well with the scope. I believe I'm 1mm over spec, and the stars are round all the way to the corners of the 268M. The vignetting is very reasonable as well. I had some concerns about the built in rotation of the focuser, so I just locked it down in a single position and use a M68 rotator. The focuser is pretty solid and I'm using a Pegasus focus motor. The drawtube has some wiggle if you try to flex it around, but I've tested it all over the sky and does not appear to be sagging or misaligned at all. I added an M68 manual rotator a few days later. I'd had one of these before and it was a little rough. This one is working great and is not imparting any tilt. I checked it with a laser rotation test on a wall in my garage, as well as in the field. I tightened all the radial plastic grub screws to make it a more wiggle-free connection. It will do in a pinch.

Next I'll need to do a broadband integration to check for CA, but this looks like a great performer to me. I'm posting the drizzled stacks and some individual subs in the revisions. Only stretch applied. I shot these bin 2x2 because that is what my dark library is built on from my longer FL scope, but I'll be switching to bin1. I did test subs at bin 1 and they are just as good.

For an 11 hour integration I pretty happy with this. I love this target because is just doesn't seem to nee a lot of processing or color tweaking. I've not been able to shoot it this wide before so I was happy to be able to get the green lagoon area in frame.

As an interesting footnote, I needed flats for my Ha data the following morning because my skyflats sequence had an error. I pointed the scope down at the snow in the middle of the dat and took flats. They worked perfectly!