Askar 91F 91mm f/6.7 Flat-Field Refractor Telescope

Askar 91F 91mm f/6.7 Quadruplet Flat-Field Refractor Telescope

The Askar 91F is a compact 91mm flat-field refractor designed to make high-quality astrophotography straightforward. Its 609mm focal length and f/6.7 focal ratio provide a versatile field of view for imaging nebulae, galaxies, star clusters, and other deep-sky targets.

At the heart of the 91F is a quadruplet air-spaced APO optical system with one ED glass element. Unlike a conventional refractor that requires a separate field flattener, the 91F incorporates its field correction into the telescope itself. The result is a 44mm image circle suitable for full-frame cameras without the need to purchase an additional flattener or precisely configure a traditional 55mm backfocus spacing. Attach your imaging train, reach focus, and you're ready to image.

Built for Astrophotography

The 91F pairs its flat-field optical system with a substantial 3" rack-and-pinion focuser featuring dual-speed adjustment and 1:10 fine focusing. A built-in 360° graduated camera rotator makes framing your target easy without disturbing the rest of the imaging train.

The telescope provides both M54 and M48 threaded imaging connections, with an M48 filter thread available for standard 2" filters.

Compact, Versatile Design

At approximately 8.6 lb (3.92 kg) for the OTA, the 91F offers enough aperture for serious imaging while remaining manageable for portable astrophotography setups. A retractable dew shield keeps the telescope compact for transport, while the included tube rings, carrying handle, and 230mm Vixen-style dovetail plate make it ready to mount.

The 91F isn't limited to imaging. Included 1.25" and 2" visual connections allow it to serve as a capable visual refractor as well.

Key Features

• 91mm aperture

• 609mm focal length

• f/6.7 focal ratio

• Quadruplet air-spaced APO optical design

• One ED glass element

• Integrated flat-field correction — no separate field flattener required

• 44mm image circle for full-frame astrophotography

• 3" dual-speed rack-and-pinion focuser

• 1:10 fine-focus adjustment

• Built-in 360° graduated camera rotator

• M54 and M48 imaging connections

• 1.25" and 2" visual compatibility

• Retractable dew shield

• 230mm Vixen-style dovetail plate

• OTA weight: 3.92 kg / approximately 8.6 lb

What's Included

• Askar 91F optical tube

• Pair of tube rings

• Carrying/accessory handle

• 230mm Vixen-style dovetail plate

• Photographic adapter set

• 1.25" / 2" visual adapter

Specifications