The 0.75x reducer can bring Askar 91F's focal ratio down to F/5, providing not only a faster focal ratio but also built-in field-flattening correction. The shorter focal ratio delivers a wider field of view and a faster exposure time, making it ideal for capturing large areas of nebulae, star clusters, and faint, fast-moving celestial objects. The 91F 0.75x reducer adopts a triplet design and supports a 44mm full-frame image circle. The back focus from the M48 thread is a standard 55mm. Both end threads are M59*1. The 91F photographic extension tube includes M54×0.75 and M48×0.75 adapters for direct and convenient connection to the 0.75x reducer. The reducer features a built-in M48*0.75 2-inch filter thread, allowing for direct filter installation and use. The entire reducer is CNC-machined and comes with front and rear metal threaded caps to protect against dust when not in use. Constructed using CNC machining, the reducer boasts a great finish and comes with front and rear metal thread caps for dust protection during storage. Specifications (After attaching) 91F Focal length 455mm (After attaching) 91F Focal ratio f/5.0 Lens Number Triplet design Back Focus 55mm (from the base of M48 male thread) Weight 0.30kg Rear-end thread type M59*1
