Having (I believe) gotten the mirrors well-collimated and having fixed a problem with a slipping focuser, I was ready to finally get an image that lived up to the promise of this scope. In that attempt I was disappointed,but the attempt perhaps revealed another, more serious problem:
something in the mirrors, and thus the collimation, is shifting as the night's work goes by. I probably should have realized this earlier (see "focuser slip comparison" and "time comparison" in the main collimation gallery), but other problems were masking it.