Askar 0.75x Reducer for the 91F Refractor - 91F-RED
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This 0.75x APO reducer takes the Askar 91F's focal ratio down to f/5. A shorter focal ratio allows the telescope OTA to have a wider field of view and faster exposure times, making it suitable for capturing large areas of nebulae, star clusters, and faint, fast-moving celestial objects.
The 0.75x reducer adopts a triplet design and supports a 44mm full-frame image circle. The overall weight is 0.23 kg. The back focus from the M48 thread is a standard 55mm. Both end threads are M59*1. The 91F photographic extension tube has two adapters, M54*0.75 and M48*0.75, which can be directly and easily connected to the 91F 0.75x reducer. At the same time, the adapter has a built-in M48*0.75 2-inch filter thread, so that you can install standard 2" filters. The reducer is CNC machined, and both ends sport threaded metal caps to protect the optics when not in use.
Specifications
| Parameter | |
| Ā 91F Focal length with Reducer | 455mm |
| 91F Focal ratio with Reducer | f/5 |
| Number of Elements | Three (Triplet) |
| Back Focus | 55mm from the base of M48 male thread |
| Weight | 0.3kg |
| Rear-end thread type | M59*1 |