ZWO 21mm M42 Extension Ring female/male

ZWO 21mm M42 Male/Female Extension Ring

This 21mm thick extension ring allows you to easily obtain the correct distance (back focus) between your ZWO camera and a field corrector.

Most correctors require sensor positioning at 55mm. However, with a back focus of generally 17.5mm on ZWO cameras, a 21mm ring is necessary.

Example configuration: ZWO optical divider (16.5mm) + ZWO extension ring (21mm) + ASI071 camera (17.5mm) = 55mm

Black anodized aluminum construction.