So I set up for the indoor star test. I used my TEC 160ED as a beam collimator for my artificial star. The TEC has exceptional correction in green. I also used my "leaning tower of barlows", which were a couple of high quality Celestron Silver Top 2x barlows stacked with a high quality Televue 2.5X barlow. I chose these barlows as they are "parafocal" with eyepieces. The barlows are used to create a point source for the star. The artificial star is then inserted into the whole stack. Both scopes are lined up. Kinda scary looking in the pictures.
A trick I've used is to leave the test scope's focus position found in DPAC alone and swap out the screen holder for a 1.25" adapter. The screen holder and adapter are of the same thickness. The plossls I use position their field stops right at the top of the 1.25" adapter opening so I figure I'm at the infinity focal point for the scope. Once the two scopes are aligned (rather easy with my laser) and the "tower" is installed in the TEC, I focus the star in the test scope by using the focuser in the TEC 160ED. Seems to work fine for what I'm doing the test for which is basically evaluating astigmatism and coma. Spherical evaluation may be a bit iffy with all of that extra glass, but so far it has correlated rather well with what I see in DPAC, at least in green light.
My only issue is my lack of experience in imaging the results. So far, I've used my Cannon 6D with a barlow but images are rather grainy due to the 3200 ISO setting I need to even see the star in live view. Sometime in the future, I'll excavated my two planetary cameras and have a go at it with them.
So, for now, just word.
The short story is that at ~150X at full aperture in green light, I saw no meaningful coma or astigmatism. Spherical correction was actually rather good with the outer first two diffraction rings close to focus being reasonably uniform in thickness and brightness and similar to each other on each side of focus. However, that central zone was having an obvious effect on the inner rings. At focus, the airy disk was fairly round and surrounded by a couple of fainter rings but the view was a little "hairy" . But it certainly didn't suck., actually, I was surprised about how nice it was. Without the green filters, well......why bother as I will never use it anywhere near this magnification at full aperture.
Stopped to 80mm this became a completely different and better scope. Still no coma or astigmatism but the diffraction patterns in green were notably more "solid" and distinct at each side of, and at, focus than at full aperture and spherical correction seemed entirely neutral and consistent with the DPAC images in green. The central zone was still visible but much better integrated into the image, especially the inner rings on each side of focus. The airy disk at focus was round, sharp, and surrounded 360 by one faint ring. Very nice. Sans filters, the extra unfocused color was obvious but the diffraction patterns were still sharp and easy to see.
So now it's time to get this scope out under some real stars.