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Askar 91F Flat-Field Astrograph

€1,089.00

Availability: In stock

Only 3 left

SKU:

ASK-91F

Askar 91F Flat-Field Astrograph: a quadruplet flat-field astrograph, light and compact, offered at a very affordable price and which can be used for visual observation and astrophotography.

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Askar 91F Flat-Field Astrograph

The Askar 91F is a refracting astrograph with an aperture of 91 mm, a focal length of 609 mm and a native focal ratio of F/6.7, designed for astronomy enthusiasts who prioritise portability and high image quality.

The Askar 91F features a four-element optical design (three front lenses and one rear lens), one of which is ED glass, which effectively reduces chromatic aberration. The Askar 91F astrograph supports an image circle of 44 mm, suitable for covering sensors up to full-frame format, offering pinpoint star images.

Thanks to its pre-flattened optical scheme, the Askar 91F astrograph eliminates the need for an additional field flattener and complex back-focus calculations. Simply connect the camera, focus and you are ready to capture images, making astrophotography easier and more enjoyable!

The Askar 91F astrograph weighs only 3.92 kg and the gross weight is 4.52 kg (including tube rings and dovetail plate). It is compact and light, making it easy to transport for observation or astrophotography, wherever your exploration takes you.

The Askar 91F is designed for both visual observation and photography. It comes with a photographic extension tube with built-in 2" filter thread and M48×0.75 and M54×0.75 adapters, making it compatible with digital SLR and astronomical cameras for quick connection and instant shooting.

The mechanical design of the Askar 91F astrograph minimises hidden user costs and ensures a smooth experience.

The Askar 91F is equipped with a retractable lens hood, which further reduces the overall length and improves portability. The inside of the tube is lined with matt felt to better eliminate stray light, while the exterior sports an elegant blue and white colour scheme with CNC machining and high-quality paint.

The handle of the Askar 91F astrograph is 130 mm long and there is a housing for the finder base. In addition, there are two finder bases on both sides of the focuser, which not only eliminate the need to disassemble it when changing the position of the scope, but also provide additional mounting positions for other astronomical accessories.

As far as the focuser is concerned, the Askar 91F is equipped with a sturdy focuser with a 3" double-speed rack-and-pinion mechanism, with 1:10 gearing. The gear knob is knurled to ensure a good grip, while the rear of the focuser features a rotator with a 360° scale for precise angle adjustment.

The dovetail plate is a 230 mm long standard Vixen/GP plate with 1/4" and 3/8" screw holes, allowing direct connection to a tripod.

The Askar 91F's rear interface includes both 2" and 1.25" adapters, allowing compatibility with a wide range of astronomical accessories.

Whether for deep-sky astrophotography, planetary observation, birdwatching or travelling, the Askar 91F is the ideal companion for exploring the world.

Technical specifications

Diameter: 91 mm.
Focal length: 609 mm.
Focal ratio: F/6.7.
Optical design: air-spaced APO quadruplet, with an ED lens..
Image circle: 44 mm.
Back-focus: in visual configuration with 2" eyepiece holder installed 122 mm (112 mm with the reduction from 2" to 1.25" installed); in photographic configuration with adapter installed 75 mm from the M48x0.75 thread stop and 93 mm from the M54x0.75 thread stop.
Focuser travel: 30 mm.
Total length: in visual configuration with 1.25" eyepiece holder installed, 513 mm with dew-shield closed and 599 mm with dew-shield fully extracted; in photographic configuration with adapter installed, 550 mm with dew-shield closed and 636 mm with dew-shield fully drawn.
Weight: 3.92 kg optical tube only, 4.52 kg with dovetail bar rings.
Photographic adapter: included, available camera-side threads: M48x0.75, M54x0.75 and M64x0.75. The adapter has an M48x0.75 internal thread for mounting standard 2" cell filters.
In the box: Askar 91F astrograph, pair of support rings, Vixen/GP type dovetail bar, set of photographic adapters