Explore Scientific 3" 0.7x Reducer Corrector
Reduces the focal length by the factor 0.7x (for f/8) and 0.8x (for f/10) respectively. The reducer/corrector not only reduces the focal length but also flattens the field.
Although originally developed for the Explore Scientific ED-APOs 127mm and 152mm, the reducer can be used with many systems. Comes with 3" barrel.
Adapters for Nikon and Canon DSLRs are available separately.
Free aperture 65mm.
If you want to attach it to a Schmidt-Cassegrain telescope via the 2" SC thread, you'd also need the following adapter ring: M54 to SC Adapter for Trutek Filter Wheel