Askar FRA600 F5.6 108mm quintuplet astrograph OTA

The FRA600/5.6 is an evolution of the FRA series, an upgraded lens has a 108mm aperture and a 600mm focal length,

The f/ratio isf/5.6, and the image circle is 66mm surpass the full frame! 

This FRA600 Quintuplet Refractor is built on a Petzval design, comprising a front triplet and rear doublet lenses, two pieces of the front lenses are ED glass. This combination provides a high level of apochromatic performance for astroimaging.

With wonderful optical design, from the FRA600 astrograph provides a 66mm image circle to ensure excellent star shape across the entire field whilst controlling chromatic aberration, minimizing the distortion.

The two lenses in the rear group have a diameter of 80mm, effectively counterbalancing the effect of decreasing field illumination. With the precise manufacturing, they obtain optimal sharpness nearly to the theoretical level, bringing you beautiful clear detailed images with round-shape stars.

The FRA600 comes with a large 4.2" rack-and-gear-based focuser which includes a standard 1:10 focal adjustment knob, the focuser greatly enhances the payload to a pro level, offering smooth operation without slipping when heavy imaging equipment and accessories are attached.

The focuser allows multiple connections. Besides, Askar also offers a standard conical extender with threads of M54×0.75 and M48×0.85 to connect various astrophotographic equipment.

Mechanically, the FRA600 has a tube diameter of 120mm and a retractable dew-shield. With the dew-shield retracted, the total length is only 493mm, making it a great portable 4" astrograph.

A set of multifunctional red anodized tube rings includes mounting points on three sides, making itself easy for attachment of accessories such as guider scope for backyard viewing.

In addition to supporting wide field astrophotography, the FRA600 is also perfect for high quality observation, providing exquisite chromatic aberration correction and creating images with impressive contrast comparable to visual experience.

The excellent performance would already justify its price if the FRA600 was a mere triplet APO refractor. But our FRA600 is a 4.3" Super APO Quintuplet Astrograph, its ingenuity has already exceeded its counterparts falling in the same price range.

From  F 5,6 to F 3,9 !!

The focal ratio of f/5.6 is already relatively fast. With the optional special ASK_ 656RD reducer you can increase the speed from f/5.6 to f/3.9 and halve the exposure time. The focal length is shortened to 421 mm.

Specifications

• Aperture 108 mm / 4.3"
• Focal length 600 mm
• Focal ratio f/5.6
• 5-element design - the 2-element corrector is permanently installed in the tube
• 66 mm image circle with full illumination and correction
• 140 mm working distance for observation with 2" star diagonal
• Long transition adapter for photography to M48x0.75 with 2" filter thread included
• Rugged 4" RAP focuser with dual speed reduction and 360° rotation
• Losmandy style dovetail bar
• Flexible tube rings with carrying handle and lateral threads for individual adaptations
• Finder shoe for standard finder bracket
• Each FRA600 comes with an inspection checklist from the manufacturer and is also tested on our optical bench
• Very sturdy flightcase