Askar SQA55 55mm f/4.8 Quintuplet APO

Quintuplet Petzval APO: A 44mm Flat-Field Image Circle

The SQA55 is built around a five-element Petzval optical design that corrects for field curvature internally. It is air-spaced and includes one piece of SD glass and one piece of ED (Extra-low Dispersion) glass, and it has great star point performance across its 44mm full-frame image circle.

Thanks to the self-flattened design you do not calculate a specific back focus: anywhere between 50mm and 60mm connection distance, you shoot once the OTA is in focus (55mm recommended). The inside of the tube has matte lines and an overall matte paint coating to minimize stray light.

f/4.8 Speed at 264mm: Capturing Wide-Field Targets

The f/4.8 focal ratio keeps exposures short. At 264mm a full-frame sensor covers about 7.8 x 5.2 degrees, enough for the Andromeda Galaxy (M31) or the North American Nebula (NGC 7000) with room around them; the large Rho Ophiuchi cloud complex is a frequent SQA55 target in customer images.

This suits Milky Way mosaics and large hydrogen-alpha regions.

Variable Aperture: 14 Blades from f/4.8 to f/22

The Askar SQA55 has a 14-blade diaphragm with a graded aperture ring from f/4.8 to f/22, and a scale on the tube that prevents accidental changes and saves the setting.

With a closest focus distance of 5m and manual focus, it also works as a telephoto lens for daytime subjects.

Dual-Speed Focuser with 360° Rotator

The SQA55 has a dual-speed focuser whose fine and coarse adjustments work independently. The fine adjustment has a central indicator point, ±1mm of travel and a locking screw. The coarse adjustment is engraved with a focusing distance scale in imperial and metric, has its own locking screw, and its handwheel has MXL-type timing teeth for driving an electronic focuser with a timing belt. For astrophotography, turn the coarse adjustment to the infinity mark; there is some leeway beyond it.

The lens tube and the 360° rotator have independent locking screws: for daily shooting the whole body rotates, and for astrophotography the high-precision rotator turns on its own, with an engraved scale for adjusting and saving the angle.

Imaging Train Integration: 55mm Back Focus and Filter Threads

Askar supports a 50mm to 60mm rear connection distance, with 55mm recommended.

• Rear Adapter: An M48×0.75 adapter at the rear.
• Filter Threads: The rear M48 adapter has a built-in 2-inch filter thread, and the front of the lens has an M67 filter thread for camera filters.

Portable at 2.18kg: Quick-Release Components & Vixen Dovetail

The SQA55 weighs only 1.84kg for the optical tube and 2.18kg with its handle and 200mm Vixen-style dovetail plate attached. It is 244mm long without the dew shield (316mm with it), and ships with a military-grade waterproof hand-carrying case.

The handle (with a multifunctional finder base slot) and the 200mm Vixen-style dovetail plate (with hand screws and a quick-release knob) come off without tools. The dew shield is held by a slot and can be stored reversed on the barrel. Four quick-release bases on the rear of the tube take accessories, and the bottom bracket has 1/4 and 3/8 screw holes for a tripod.