CHF 139
In stock with supplier
Visit Askar 91F 0.75× Reducer is a focal reducer specially designed for telescopes. Askar 91F Flat-Field. This accessory transforms the astrograph into a faster, brighter and more versatile system, ideal for wide-field deep-sky astrophotography.
Thanks to its 0.75×, it increases the focal ratio from 91F to f/5, This is combined with advanced field correction to produce fine, uniform stars on all modern Full Frame sensors.
The wider photographic field and shorter exposure times make this reducer particularly interesting for imaging large nebulae, star clusters and faint deep-sky objects.
Once installed on the Askar 91F, the reducer reduces the native focal length:
This reduction brings several important benefits:
The reducer is particularly useful for photography:
The Askar 91F 0.75× Reducer does more than just reduce the focal length. It also incorporates a field correction that effectively limits field curvature and preserves excellent star quality right into the corners.
This design guarantees :
The supported image circle reaches 44 mm, perfectly suited to full-format 24×36 mm sensors.
The reducer is based on an optical formula with three lenses specially optimized for the Askar 91F.
This design enables :
The result is a clean, uniform image across the entire photographic field.
The Askar 91F 0.75× Reducer uses a standard backfocus of 55 mm measured from M48 male thread.
This distance facilitates integration with most modern astrophotographic equipment:
The 91F photographic tube includes :
Installation of the gearbox is fast and particularly simple.
The reducer incorporates a standard thread M48x0.75 compatible with 2-inch astronomical filters.
This allows direct installation of :
This compatibility greatly simplifies the design of the optical train.
Like other Askar premium accessories, the 91F 0.75× Reducer benefits from precision CNC manufacturing ensuring :
The gearbox is supplied with front and rear threaded metal plugs to protect the optical surfaces from dust and moisture during transport and storage.
Both ends are threaded M59x1, guaranteeing :
This design helps maintain optimum image quality even with advanced imaging configurations.
| Features | Value |
|---|---|
| Compatibility | Askar 91F Flat-Field |
| Reduction factor | 0.75× |
| Resulting focus | 455 mm |
| Resulting focal ratio | f/5 |
| Optical type | Triplet corrector/reducer |
| Image circle | 44 mm Full Frame |
| Backfocus | 55 mm from M48 male thread |
| Main thread | M59x1 |
| Compatible adapters | M54x0.75 and M48x0.75 |
| Filter compatibility | Integrated 2″ M48 filter thread |
| Weight | 0.3 kg |
| Manufacturing | High-precision CNC aluminum |
The Askar 91F 0.75× Reducer is an excellent complement for astrophotographers wishing to exploit the full potential of their Askar 91F.
By transforming the telescope into a fast astrograph at f/5 while retaining excellent Full Frame correction, this reducer greatly enhances the instrument's versatility and photographic efficiency.
Its modern optical design, robust mechanics and perfect compatibility with the 91F make it a particularly coherent accessory for deep-sky enthusiasts looking for simplicity and performance.
