The Askar FRA400: A Flat-Field Refractive Astrograph

This portable, Askar FRA Quintuplet series telescope is a premier astrograph designed to deliver quality flat-field images during astrophotography sessions. FRA, which stands for “Flat-Field Refractive Astrograph” provides built-in flat field correction. Askar has utilized a Petzval-like quintuplet design, with two lenses made of special extra-low dispersion ED glass on this 72 mm f/5.6 refracting optical tube. Full-frame imaging is supported, with a 44 mm image circle.

Using a design similar to Petzval means the OTA is excellent at controlling and diminishing chromatic aberration. This modern optical design includes a retractable dew shield and a 3″ rack-and-pinion, high-precision focuser with a 360-degree rotator. This is a very convenient feature, as it allows a connected camera or other accessory to be rotated to the best or most comfortable orientation. The focuser comes equipped with fine focus adjustment for obtaining desired focus for astro-imaging or visual observation.

Everything Needed to Integrate the FRA400 Into Your Astrophotography Setup
Included with the astrograph are a pair of red anodized tube rings with integrated carrying handle. Additional accessories include an M68 to M48 adapter, a 2″ to 1.25″ adapter, and a dovetail plate. With all accessories, the total weight of this system is slightly over six pounds, making it lightweight and portable.

Novel Quintuplet Optical Design

The Askar FRA400 adopts a novel, Petzval-like optical design. With a 72 mm aperture, this quintuplet refractor features 5 elements in a 3+2 configuration. Two of the three front elements are made from extra-low dispersion (ED) glass to significantly reduce chromatic and other aberrations. Additionally, there is built-in flat field correction, eliminating the need for an additional field flattener accessory.

Several Helpful Accessories Included

The FRA400 also comes with several accessories to help better integrate the optical tube to your astrophotography setup. Included with the optical tube are tube rings with carry handle, a retractable dew shield, a 150 mm dovetail plate, an M68 to M48 adapter, a 2″ adapter, a 2″ to 1.25″ adapter, and a manual. Also integrated into the focuser is a 360-degree rotator, which allows you to rotate a connected camera or other accessory to the desired orientation.

What’s in the box
Askar 72 mm Quintuplet APO Astrograph
Tube Rings
M68 to M48 Adapter
2″ Adapter
1.25″ to 2″ Adapter
Handle
150 mm Dovetail Plate
Inspection List
Manual