dagerber

OK, got my first image with the reducer and the stars look actually pretty good! Taken with Skywatcher Esprit 120 ED, the 0,77 Reducer and Optolong L-extreme. 4.8h integration time. See https://www.astrobin.com/oej14k/

OK, thank you. I also contacted Skywatcher, they replied the 95mm is measured from the edge as shown below.

Hi @Sp@ce_d I have the reducer for the Esprit 120. I've not used it yet, so I looked up how to hook up the camera with correct backfocus. https://www.skywatcherusa.com/products/0-77x-reducer-flattener-for-esprit-120 says "95mm back-focus (55mm when back focus spacer and M48 ring installed)" I think 95mm is wrong and it should be "80mm back-focus (55mm when back focus spacer and M48 ring installed)" Drawing top: Reducer + Focus-spacer + M72/M48 Adapter => 55mm backfocus Drawing bottom: Reducer + M72/M48 Adapter (without the Focus-spacer) => 75mm backfocus Here my setup with an ASI2600MC that I hope I got right: My Off-axis guider "collided" with the focus-spacer and adapter ring of the reducer because they have quite a substantial diameter. I guess a M68 Off-axis guider would work, but mine is the small one. Therefore I removed the focus spacer that came with the reducer and added a 20mm spacer instead after the M48 Adapter ring. What do you think? Daniel