M54M-M54F-16.5 Adapter

Threaded perfectly onto my ASI2600MC-Duo with zero play, and the 16.5mm spacing put my backfocus exactly where it needed to be. Solid aluminum, light enough to not strain the focuser, and it feels machined with real care—no burrs or wobble. Exactly what I needed for a clean optical train.

Finally got the spacing dialed in on my ASI2600MC-Duo thanks to this adapter. The 16.5mm optical length was exactly what I needed to eliminate star halos in my narrowband images.

The 16.5mm spacing sits perfectly between my camera and telescope, and the threads are buttery smooth—no tilt or play at all on the ASI2600MC-Duo. I've finally got my backfocus dialed in without shimming around.