Askar FRA500 Quintuplet Astrograph

Askar FRA500  Quintuplet Astrograph

Sharpstar Optics presents the Askar FRA500, the latest astrograph in the FRA series. With a 90 mm aperture and a 500 mm focal length at f/5.6, it offers better deep-sky performance than the FRA400 while remaining more compact and lighter than the FRA600, making it ideal for mobile observing and imaging.

The FRA500 inherits the optical qualities of the FRA family. It uses an air-spaced quintuplet Petzval three-plus-two design. The front group features three lenses including two ED elements for effective aberration control. The rear group of two spaced lenses ensures uniform sharpness across the field with almost no edge distortion.

The FRA500 supports an impressive 55 mm image circle, larger than full frame. Its fixed backfocus simplifies use as no spacing calculation or extra adapter is needed — just focus and capture.

Mechanically, the FRA500 combines practicality and aesthetics. The tube layout is clean, with a dew shield accented by a red ring. Total length is 452 mm extended and 410 mm retracted.

At the rear, a 3.5-inch dual-speed focuser provides precise and stable focusing. Internal graduations are easy to read, and a finder base allows mounting guiders or accessories.

The FRA500 comes with tube rings, a top handle and a Losmandy-style dovetail plate. The ivory tube, glossy black focuser and red accents give it a distinctive appearance.

At 4 kg and 410 mm long, it is easy to carry and ideal for portable setups. Like other FRA models, it is appreciated for its fast optics, corrected field, solid mechanics and high-quality imaging performance.

FRA500 SPECIFICATIONS

• Aperture diameter : 90 mm
• Focal length : 500 mm
• Focal ratio : f/5.6
• Objective : air-spaced quintuplet APO including two ED elements
• Image circle : 55 mm
• Maximum connection distance
• 85 mm from the base of the M48×0.75 thread
• 158 mm from the base of the M86×1 thread
• Total length : 452 mm (410 mm dew shield retracted)
• OTA weight : 4.1 kg
• Total weight with rings and dovetail : 5.2 kg
• Rear thread : M86×1
• Conical adapter : M48×0.75

Package contents

• FRA500 OTA
• Pair of tube rings
• Handle
• Askar Losmandy dovetail plate
• Conical adapter
• Manual