QHY OAG-S, Small Off-Axis Guider
The "Small" version of the QHY OAG has a diameter of 54mm, and will only work with M42/0.75 adapters. This means it supports camera models with sensors smaller than APS-C format, which includes the QHY21/22/23, the QHY9, the QHY8/10/12 and any other model that has a sensor size of less than APS-C.
The QHY OAG has an 8mm x 8mm multi-coated prism. Its position can be adjusted as desired and then locked into position with a thumbscrew. This OAG also comes with a locking multi-thread 1.25" focuser with an approximate range of 6mm. If you use the QHY5L-II as your guide camera, its position is adjustable when inserted into the QHY OAG-S. These two adjustments will give you a wide range of back focus.