Askar 60F Flat-Field Astrograph

A 60mm Astrograph for Full-Frame Imaging

The Askar 60F is designed, in Askar's words, for astronomy enthusiasts who prioritize portability and high image quality. With its 60mm aperture, it strikes a balance between light-gathering power and a compact form factor, and Askar designs it for both visual observation and photography.

This astrograph is primarily for imagers using cameras with sensors up to full-frame (36x24mm), thanks to its generous 44mm corrected image circle. It simplifies the entire imaging process by integrating the field flattener directly into the optical design, removing a separate flattener from the setup. This makes it a powerful choice for both seasoned imagers seeking a reliable travel scope and those new to the hobby who want a system that works correctly out of the box.

Quadruplet APO Optics: 4-Element Design with ED Glass

At the heart of the Askar 60F is its quadruplet air-spaced apochromatic (APO) objective. This design consists of four lens elements (three in the front group and one in the rear) to achieve a high degree of color correction and field flatness. One of the elements is made from Extra-low Dispersion (ED) glass, which significantly reduces chromatic aberration, or false color fringing, around bright stars and other high-contrast objects.

The 60F supports 44mm full-frame imaging with great performance of the surrounding star points.

The 408mm Focal Length at f/6.8: Image Scale and Exposure

The 408mm focal length provides a versatile image scale that is well-suited for a wide range of deep-sky objects. It is long enough to resolve details in larger galaxies and planetary nebulae, yet wide enough to frame expansive targets like the Andromeda Galaxy (M31) or the North American Nebula (NGC 7000), especially when paired with an APS-C or full-frame sensor.

The native f/6.8 focal ratio is a deliberate design choice that balances imaging speed with optical correction. It is fast enough to capture significant detail in your sub-exposures without being so aggressive that it becomes overly demanding on your mount's tracking accuracy. A moderate focal ratio is also forgiving of focus and spacing.

The 44mm Corrected Image Circle: No Flattener Required

A key feature of the Askar 60F is its "flat-field" design. The integrated rear optical element acts as a field flattener, correcting for the natural field curvature inherent in refracting telescopes. This gives a flat field across a 44mm image circle, large enough to cover a full-frame sensor.

This integrated solution offers two major advantages. First, it eliminates the need to purchase a separate, compatible field flattener. Second, it removes the complexity of calculating and setting the precise back focus distance between a flattener and the camera sensor. With the Askar 60F, you simply attach your camera via the included adapters, bring the image to focus, and you are ready to shoot.

Adapters and Back Focus: 81mm from the M48 Male Thread

The Askar 60F simplifies camera connection with a comprehensive set of included photographic adapters. The adapter set starts from an M64×0.75 to M54×0.75 adapter and steps down to M54×0.75 and M48×0.75; this makes it compatible with DSLRs and astronomical cameras.

Because the flattener is built-in, back focus is straightforward. The design allows for a maximum accessory connection distance of 81mm from the base of the M48x0.75 male thread, or 99mm from the M54x0.75 male thread. These are maximum figures with the focuser fully retracted; plan the optical length of off-axis guiders, filter drawers or filter wheels within them. For added convenience, the M48 adapter includes an internal thread for mounting standard 2-inch filters.

The 2.4-inch Focuser: 50mm of Travel and 360° Rotation

Precise focus is critical in astrophotography, and the Askar 60F is equipped with a robust 2.4-inch dual-speed rack and pinion focuser to achieve it. The focuser is rigid. It offers 50mm of drawtube travel, sufficient for reaching focus with a wide variety of cameras and accessories.

Fine-tuning is accomplished via the 1:10 micro-focusing knob, allowing for the tiny adjustments needed for fine focus; the knob has an anti-slip cover. For framing your target, a 360° rotator is integrated into the focuser body, complete with a degree scale and locking screw. This lets you rotate your entire imaging train to the desired orientation without having to loosen the camera connection. The manual marks the screw positions that can be used for electric focusing bracket installation.

Optional 0.75x Reducer: A Faster f/5.1 System at 311mm

For imagers seeking a wider field of view and faster imaging times, Askar offers an optional 0.75x focal reducer designed specifically for the 60F. This triplet reducer transforms the telescope's optical parameters:

• Focal Length: Reduces from 408mm to a much wider 311mm.
• Focal Ratio: Speeds up the system from f/6.8 to a fast f/5.1.

At f/5.1 the same exposure takes about 56% of the time needed at f/6.8. The reducer supports a 44mm full-frame image circle, has M50×1 threads on both ends and a standard 55mm back focus from the base of the M48 male thread, and connects directly to the included 60F photographic extension tube.

Building Your Imaging Train with the Askar 60F

The Askar 60F is designed for flexibility. The ample 81mm of back focus available from the M48 adapter gives room to build an imaging train. You can easily incorporate essential accessories between the telescope and your camera.

A typical deep-sky imaging setup might include connecting an off-axis guider for precise tracking, followed by a filter drawer or electronic filter wheel for narrowband or LRGB imaging, and finally your primary astronomy camera. The included M48 adapter with its built-in 2-inch filter thread offers the simplest configuration for one-shot color or monochrome imaging with a single filter. Threaded connections keep the imaging train secure.

Mechanical Design: 230mm Vixen Plate and Dual Finder Bases

The Askar 60F is built with practical use in mind. The optical tube is protected by a retractable dew shield that reduces its length for storage and blocks stray light during use. The inside of the tube is pasted with matting felt to further enhance contrast by absorbing internal reflections.

It comes with tube rings, a carry handle and a 230mm Vixen-style dovetail plate, and the tube has a blue-and-white finish with CNC machining and paint. For mounting accessories, the 60F offers:

• Dual Finder Bases: Two separate finder bases are mounted on either side of the focuser, providing flexible placement for a guide scope or finder scope.
• Handle Slot: The carry handle also features a slot for an additional finder-style base.
• Tripod Mounting: The dovetail plate includes standard 1/4"-20 and 3/8"-16 threaded holes for direct mounting to a photo tripod for visual use or wide-field captures.

Portability Profile: 2.86kg Gross Weight and 289mm Length

Weighing in at just 2.36kg for the optical tube assembly (OTA) and 2.86kg with rings and dovetail, the Askar 60F is a portable astrograph, with a minimum length of 289mm when the dew shield is retracted.

With this low weight you can assemble a complete, high-resolution deep-sky imaging rig that is easy to transport to dark-sky locations and quick to set up, maximizing your time under the stars.

First Night Out with the Askar 60F

Thanks to its integrated design, setting up the Askar 60F for your first imaging session is remarkably simple. After mounting the telescope to your equatorial mount and achieving a rough balance, you can attach your camera using the appropriate adapter from the included set.

With the camera attached, point the telescope at a bright star and use a Bahtinov mask to achieve critical focus with the dual-speed focuser. Once focused, use the 360° rotator to frame your deep-sky target. Because there is no external flattener to adjust, your system is now ready for imaging. This streamlined process removes common sources of frustration and lets you spend more time capturing data.