What is the size of the threads on the front of the AO-8? I'm upgrading the focuser on my scope and I need to purchase the correct threaded adapter to connect from my focuser to the AO-8. If possible I'd like to avoid using the adapter plate to keep backfocus to a minimum. I'm currently not using an adapter plate and I have a 2" nosepiece screwed into the front of the AO. I'd like to avoid a trip to the observatory and needing to remove the camera from the scope to measure the threads if possible. Is there any problem with threading an adapter directly into the AO-8 without using an adapter plate? Thanks!
The telescope-facing side of the AO-8 has these possible ways of attachment: a) The original arrangement included a T-thread adapter block (M42 x 0.75 mm thread size) and a T2 nosepiece that screwed into it. b) The larger inner-diameter one-piece 2-inch bolt-on nose piece: https://diffractionlimited.com/product/ao-8-2in-nosepiece-adapter/ that bolts on in place of the adapter block c) Use the four machine screw holes (for #4-40 thread, about 1/4 long with washers so nothing hits the inside parts) and build your own adapter. d) Remove all the adapters and use the STL-thread hole in the body itself. The thread size is 2.156″ x 24tpi. You don't want to have anything protrude deeply into this - it will hit the moving window and that will be destructive. I don't usually recommend option d) as long threads will cause interference or damage.