Astronomy Specialist

ASKAR FRA600 F/5.6 APO REFRACTOR

$4,299.00

Quantity
- +

 

The Askar FRA 600 f/5.6 is a professional apochromatic Petzval quintuplet refractor with an aperture of 108mm and a corrected field of 66mm in diameter.

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

Differently from standard ED refractors, the Askar 600 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 an extra large 66mm 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 4.2" 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 focuser is compatible with the ZWO EAF electronic focuser bracket.

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.

Askar FRA-600 with Nikon D850 camera

 

Every Askar telescope is inspected on the optical bench by Testar and is guaranteed against defects. To ensure optimal performance, we test every single telescope on an optical bench, using an artificial star in autocollimation. This test can easily reveal the presence of optical defects such as spherical aberration, astigmatism, zonal errors, coma or optical elements out of collimation. The light from the artificial star travels from the eyepiece holder through the lenses and it gets reflected by a high quality Zerodur flat mirror with a correction peak-to-valley of λ/20. Then, the light travels back through the lenses, gets divided by a beam splitter, then is magnified by a high quality Barlow and finally analyzed with an eyepiece and a camera. This is a test in double pass and any optical aberration gets magnified twice and therefore optical errors can be easily detected. 

 

 

 

Recommended accessories :

 

Optical design

Apochromatic Quintuplet dual ED air spaced

Objective diameter

108 mm

Focal length

600 mm

Focal ratio

f/5.6

Resolving power

1.07 arc second

Stellar limiting magnitude

12.87

Max. magnification

270 x

Light gathering power

238 times the human eye

Mount attachment

Losmandy style bar

Focuser

Rack & pinion dual speed (10:1) 4.2" diameter

Camera connection

Conical extension tube with M54 x 0.75 & M48 x 0.75

Backfocus

160 mm

Tube weight

7.9 kg (including tube rings and dovetail bar), 6.5 kg without accessories

Tube length

493 mm

Tube diameter

125 mm

Dew shield diameter

147 mm

SKU

AS-FRA600

 

   


 

 

  • Askar 600
  • Tube rings
  • Losmandy style dovetail bar
  • Carrying handle
  • Adapter to 2" and 1.25"
  • Adapter from M90 x 1 to M54 male
  • Adapter from M54 to M48 male
  • Conical adapter with separate M68, M54 & M48 thread sections

 


 

-M31 | Askar FRA600 Quintuplet Astrograph. 

 

Sharpless 2-308 - Michael Fong, Askar FRA 600 + ZWO ASI6200MM

 

Sh2-308 by Michael Fong | Askar FRA600 + ZWO ASI6200MM.

 

 

Sh2-308 by Davide Mancini | Askar FRA600, ZWO ASI2600MM, Optolong filters, 10 Micron GM2000HPS.
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