Askar FRA600 108mm f/5.6 Quintuplet APO

A 5-Element Petzval System with 2 ED Elements

The core of the FRA600 is its 5-element (quintuplet) optical system, built on a Petzval design. It uses a front triplet and a rear doublet, two of them ED (Extra-low Dispersion) glass, which provides a high level of apochromatic performance for astroimaging.

The field flattener is built in, so there is no external flattener to buy or space and no back focus to calculate.

108mm Aperture at a Native f/5.6

The 108mm aperture gathers light for faint detail, and the 600mm focal length suits a wide range of targets at a native f/5.6.

With a full-frame sensor the field is about 3.4 x 2.3 degrees, which frames the Andromeda Galaxy (M31); the whole Cygnus Loop needs a mosaic.

A 66mm Image Circle

The FRA600's 66mm image circle ensures excellent star shape across the entire field while controlling chromatic aberration and minimizing distortion. It covers the full-frame (36x24mm) format with margin.

• Full Frame: The 66mm circle covers full-frame DSLR, mirrorless and astronomy camera sensors.
• No Separate Flattener: The Petzval design provides its own field correction, so there is no external flattener to buy or space.
• 80mm Rear Group: The two rear lenses are 80mm in diameter, which counterbalances the fall-off in field illumination.

160mm of Back Focus and Adapter Versatility

The back focus is 160mm, measured from the end of the rotator's M90x1 male thread to the focal plane. Your off-axis guider, filter drawer and camera sit within it, and there is no need to calculate the back focus. Without the rotator, the focuser also offers an M108x1 male thread.

Askar includes a sectional conical adapter that steps M90×1 to M68×1, M54×0.75 and M48×0.75. For visual use, 2" and 1.25" adapters are included for diagonals and eyepieces.

The 4.2" Rack-and-Pinion Focuser

The FRA600 has a large 4.2" rack-and-pinion focuser with a standard 1:10 fine adjustment knob. It raises the payload to a pro level and operates smoothly without slipping with heavy imaging equipment attached.

For framing your target, a 360° rotator is integrated into the focuser assembly. This lets you set the camera angle without loosening the imaging train.

The Optional Askar 0.7x F3.9 Reducer

For imagers seeking an even wider field of view and faster imaging times, the Askar FRA600 works with the optional Askar 3" F3.9 Full Frame Reducer. This 4-element 0.7x reducer gives 420mm at f/3.9, so the same exposure takes about 49% of the time needed at f/5.6. It supports a 44mm image circle, has a standard 55mm back focus and a built-in M48×0.75 2-inch filter thread.

A 493mm Tube

The optical tube has a diameter of 125mm and measures 493mm with its dew shield retracted; it is a great portable 4" astrograph. It comes with a pair of multifunctional red anodized tube rings, a multi-functional handle and a dovetail plate.

• Retractable Dew Shield: Retracts for transport.
• Tube Rings: Mounting points on three sides for accessories such as a guide scope.

6.5kg with Rings and Dovetail

The total weight of the FRA600, including the tube rings and dovetail plate, is 6.5kg.

Its 493mm retracted length makes it easy to take to dark-sky sites.