Astronomy Specialist




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The Askar FRA 500 f/5.6 is a professional apochromatic Petzval quintuplet with an aperture of 90mm and a corrected field of 55mm in diameter.

The lenses are assembled in two groups: an air-spaced triplet on the front and a  correcting doublet towards the focus. The objective lens includes two Extra Low  Dispersion glass for a superb chromatic correction.

Differently from standard ED refractors, the Askar 500 features a Petzval design that does not require to set the sensor to a specific distance to the last lens. That leaves the freedom to use any filter wheel, any off-axis guider or accessory without any worry to calculate the correct distance from the flattener. 

With a large 55mm fully corrected image circle and a focal ratio of f/5.6, this is the perfect astrograph for the advanced astrophotographer. The large rack and pinion 3.5" focuser has a high payload capacity, it can be rotated 360° to perfectly frame the subject and it has a reduction gear of 10:1 for precise focusing.

The FRA500 can be used with the ASKAR F/3.9 Reducer for FRA400 & FRA500.

All the lenses are fully multi-coated and the tube is internally blackened to reduce reflections and absorb stray light. The tube is made of aluminium, the rack and pinion focusing mechanism of brass and the mechanical components are engineered to provide the best rigidity, performance and durability.



Optical design

Apochromatic Quintuplet dual ED air spaced

Objective diameter

90 mm

Focal length


Focal ratio


Image circle

55 mm

Mount attachment

Losmandy style bar


Rack & pinion dual speed (10:1) 3.5" diameter

Camera connection

M68 x 1 male, M54 x 0.75 male, M52 x 0.75 female, M48 x 0.75 (with 2" filter thread)


158 mm from base of M68 x 1 thread, 85 mm from base of M48 x 0.75 thread on rotator

Tube weight

5.2 kg (including tube rings and dovetail bar)

Tube length

452 mm (410 mm with dew shield retracted)

Tube diameter

105 mm

Dew shield diameter

120 mm








  • Askar FRA500
  • Tube rings
  • Losmandy style dovetail bar
  • Handle on the rings
  • Conical extender from M86 x 1 to M68 x 1
  • Conical extender from M68 x 1 to M54 x 0.75
  • Conical extender from M54 x 0.75 to M52 x 0.75
  • Adapter from  M52 x 0.75 to M48 x 0.75
  • Manual

ZWO camera software ASKAR FRA500 manual (coming soon)


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