Got the Circus Cannon to the roof. A 10″ f/5 dobsonian. Originally, it used two metal springs to hold the telescope in place on the altitude bearings. I removed the springs, and wound a three-foot bungee twice around the rear of the telescope. Then I inserted 11 three-inch fender washers as a counterweight. This worked, and still works. The telescope balances in every position. With the original 1″ 1/4 adapter, the logitech fusion webcam did not achieve focus. A 3/4″ recessed adapter solved this, and I had my first session on the roof using the dob for astrophotography. Twenty-one exposures; 7.2 Gb in about an hour of fiddling with exposure, gain, pointing.
I believe this is a 1/500 second exposure with ir filter. 380 frames, best 249 stacked. The dob has no tracking, so the camera scans the moon. The stack expands the image size. 704 x 576 capture size.