A November 2022 Redcat 51. With an objective of 51mm, 250mm focal length with a focal ratio of f4.9, these are ideal for wide-field astronomical imaging with either an APS-C or full-frame DSLR, mirrorless, or dedicated astronomy cameras.

This one includes a Nikon T-ring for DSLR. With some extras not included here, the 51 can reportedly be used for visual astronomy, I've not tried that.

It carries the standard Redcat helical focuser and an inbuilt Bahtinov mask for fast and precise focusing. An Optolong L-Pro filter for reduced light pollution and a USB powered Dew Heater are included as well as a Deep Sky Dad mount for an ASIAir mini.

The 51 is small enough to be a breeze to take it out into the dark sky areas away from town and is an easy load for a star tracker. This is a step up from a large camera lens in terms of portability and sharpness of focus.