Askar 91F 91 mm f/6.7 Quadruplet Flatfield Apochromat - with optics test

Askar 91F 91 mm f/6.7 Quadruplet Flatfield Apochromat

Astrograph with an aperture of 91 mm, a focal length of 609 mm, and a native focal ratio of f/6.7

The optical design of the Askar 91F features a four-element configuration (three elements in the front and one in the rear), including one piece of ED glass, which can effectively reduce chromatic aberration. It supports 44 mm full-frame imaging with great performance of the surrounding star points.

The Askar 91F is a self-flattened design that allows users to avoid calculating the back focus and buying additional flatteners. After attaching the imaging accessories, users can directly use it for shooting after the OTA is in focus. This further reduces the cost and improves the pleasure of photography.

Lightweight instrument for visual use
The Askar 91F strikes a balance between practicality and versatility while achieving lightweight portability through its compact design. The OTA weighs just 3.92 kg, with a gross weight of 4.52 kg (including the tube rings and dovetail plate).

The Askar 91F is versatile in its use, allowing for both visual observation and astrophotography. For user convenience, it comes standard with three visual accessories: an 8 mm eyepiece, a 20 mm eyepiece, and a 1.25-inch erecting prism.

The 8 mm eyepiece has a magnification of 76x and the 20 mm eyepiece has a magnification of 30x. The Askar 91F can be used with different eyepieces depending on the target, and both eyepieces are ideal for viewing birds and landscapes.

Both eyepieces are 1.25 inches and have a soft rubberized top for comfortable use.

The 1.25-inch erecting prism provides correct left-to-right and down-to-up image views, making users easy for you to conduct terrestrial and astronomical observations without the hassle of seeing images reversed up, down, left, and right.

Hassle-free astrophotography
The Askar 91F also comes standard with a photographic extension tube with a built-in 2-inch filter thread for easy shooting connections, providing M48×0.75 & M54×0.75 adapters to accommodate various DSLR cameras and professional astronomical cameras, meeting diverse imaging needs.

Practical mechanics
The mechanical design of the Askar 91F itself adheres to Askar´s consistent philosophy of taking into account the user´s habits and minimizing the user´s invisible costs.

The Askar 91F features a retractable dew shield, further reducing overall length and enhancing portability. The inside of the tube is pasted with matting felt to better eliminate stray light, while the exterior sports a sleek blue-and-white color scheme with high-quality CNC machining and paint finish.

The Askar 91F´s handle is 130 mm long and has a finder base slot. Besides, there are two finder bases on both sides of the focuser, which not only eliminates the need for disassembling when changing the position of the finder scope but also provides additional mounting positions for other astronomical accessories.

In terms of the focuser, the Askar 91F is equipped with a rigid dual-speed R&P 3-inch focuser, which has a 1:10 fine adjustment and a 360° scaled rotator at the rear end for precise angle adjustment.

The rear interface of the Askar 91F includes both 2-inch and 1.25-inch adapters, enabling compatibility with a wide range of astronomical accessories.

The 230 mm Vixen-style dovetail plate includes 1/4" and 3/8" screw holes for direct tripod mounting.

This is how Teleskop-Service guarantees the consistently high quality of the refractor:

The mechanics are tested, the focuser is optimally adjusted.

The lens is cosmetically checked and cleaned. We also check that all counter screws are correctly tightened. These often loosen during transportation.

The optics are collimated and the result is checked on the optical bench. The telescope is given a serial number.

A complete optics test is carried out, which is enclosed with the telescope (star images and ronchi image on the optical bench in autocollimation).

Only then are the telescopes handed over to the warehouse and prepared for dispatch.

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

Promotion video
The manufacturer has released a video about this telescope:

- 91F Apochromat, OTA
- CNC rings with carrying handle and 230 mm long Vixen style dovetail bar
- Set of thread adapters
- Adapter M64 thread to 2" receptacle
- Adapter 2" to 1.25" receptacle
- 1.25" 45° erecting prism
- 1.25" eyepiece set, 20 mm and 8 mm focal length
- User´s manual
- Inspection check list
- Certificate card
- Product warranty
- Cardboard box

Safety informations: PDF Download