This field flattener/reducer is for use with the William Optics Zenithstar 73 OTA. It is adjustable so you can set the right spacing that you need for your camera without the need for extension tubes. This FLAT73R is full frame ready! It was designed with full frame chip-size DSLR cameras in mind. It will deliver an image circle of >44 with a 36×24 mm sensor.
The back focus distance is 56.8 mm with an adjustment distance for DSLR and Mirrorless Cameras is 1.8 mm. Threads: Side A = M63 male. Attaches to your telescope and is the camera rotator side. Your must first remove the eyepiece adapter and adapter ring from your telescope. Un-twist them after removing the three small screws in the ring collar. This will expose the M63 female filter threads. Side B (attaches to your camera or other accessories) = M48 male.
Install your filter to the M48 filter threads in the center of the reducer-flattener by twisting the rotator and removing the narrower section of the reducer. A filter with M48 threads will fit in the center section and not add to your backfocus. Suitable for several types of CCD and CMOS astro-cameras with their accessories, also M4/3, Sony a, Nikon, Pentax, Canon, and Fujifilm.