Askar 0.75× Reducer for 91F

Askar 91F 0.75× Reducer

This 0.75× reducer is designed specifically for the Askar 91F. Its triplet design corrects the photographic field across a 44 mm full-frame image circle. With the matched telescope, Askar publishes 455mm focal length and f/5.

Optical configuration

Reduction widens the photographed field and lowers the focal ratio while providing field correction. It is a matched optical accessory, rather than a universal reducer for other telescope models.

Connections and filters

The optical unit has M59×1 at both ends of optical unit. It works with the 91F photographic extension assembly, whose M54×0.75 and M48×0.75 adapters provide the camera connection. The built-in M48×0.75 thread accepts a 2-inch filter.

Sensor spacing

Set 55 mm from the base of the M48 male thread to the sensor. This reference applies to the stated M48 camera arrangement; changing the adapter changes the reference face. Include all intervening adapters and optical components when arranging the train.

Construction and storage

The CNC-machined housing has threaded metal caps at both ends for dust protection during storage. The manufacturer technical table lists a weight of 0.3kg. Telescope, camera and filters are separate equipment.

Askar manufacturer documentation

Compatibility notes

Only the matched Askar 91F configuration is verified. 55 mm backfocus is measured from the M48 male thread base. The manufacturer table gives the rounded reduced focal length as 455 mm and focal ratio f/5; these are retained as published.