Astronomy Specialist

ASKAR 91F f/6.7 APO REFRACTOR

Regular price $1,799.00AUD
SKU: AS-91F

Askar

Apochromatic Petzval quadruplet

3.92 kg


 

The Askar 91F is an apochromatic quadruplet flat-field astrograph that offers high performance for an exceptionally low price. The quadruplet design makes it perfect for both visual observation and astrophotography. The objective lens features an element of extra-low dispersion glass (ED) that minimizes chromatic aberration. 

 


The Askar 91F is a versatile instrument and excels not just at imaging, but as a grab & go visual telescope. The included 1.25" erecting prism plus 8mm and 20mm eyepieces make this a great option for landscape and bird viewing.

 

 

The OTA itself weighs just 3.9kg (4.5kg with tube rings and dovetail bar) and has an overall length of 513mm with the dew shield contracted, making it easy to transport.

 

 

Unlike traditional refractors, the quadruplet design does not require a separate field flattener and you do not need to calculate precise backfocus. With a large image circle of 44mm, the Askar 91F is a highly capable imaging telescope.

The 3" dual-speed rack & pinion focuser is precise and rigid. It is natively compatible with most motorized focusers on the market including the ZWO EAF. The focuser includes 2" and 1.25" visual adapters as well as M48 and M54 camera adapters. On the rear there is a 360 degree rotator with fine rotation angle markings for precise framing. A 2" mounted filter can be attached to the rear M48 camera adapter.

 

 

Unlike most refractors, the 91F includes two finderscope bases on either side of the focuser, allowing you to attach both a standard guide scope and control unit such as the ASIAIR without the need for additional accessories. The handlebar also includes a finder-style slot, allowing for even more possibilities.

 

 

The inner surfaces of the retractable dew shield are covered with matte felt and the interior of the telescope tube has matte paint and internal baffles, to reduce internal reflections and light scattering.

Note: the mount shown in the product images is not included with the telescope.


 


Specifications

 

Optical design

Apochromatic air-spaced quadruplet with ED glass

Objective diameter

91 mm

Focal length

609 mm

Focal ratio

f/6.7

Resolving power

1.63 arc second

Stellar limiting magnitude

11.96

Max. magnification

177.5 x

Light gathering power

102.88 times the human eye

Mount attachment

230 mm Vixen-style dovetail with 1/4"-20 & 3/8" screw holes

Focuser

3" rack & pinion dual speed 1:10

Tube weight

3.92 kg (4.52 kg with dovetail and rings)

Tube length

609 mm (636 mm with dew shield extended and photographic adapters)

Tube diameter

91 mm

Dew shield diameter

114 mm

Connections

2", 1.25", M64 x 0.75, M54 x 0.75, M48 x 0.75

Focus point (imaging mode)

75 mm from M48 thread, 93 mm from M54 thread

Focus point (visual mode)

112 mm from 1.25" adapter, 122 mm from 2" adapter

SKU

AS-91F

 




 Items included

  

 

  • 91F OTA
  • Pair of tube rings
  • 230mm Vixen bar
  • 2" visual back
  • 1.25" eyepiece adapter
  • M64 - M54 adapter
  • M54 - M54 adapter
  • M54 - M48 adapter
  • 1.25" erecting prism
  • 1.25" 8mm Plossl eyepiece
  • 1.25" 20mm Plossl eyepiece
  • Manual
  • Soft carrying case
Instructions

 

    Downloads

     

     Instruction manual