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FRA400

Category： Askar

Welcome to our brand new Askar FRA series! The FRA, which stands for “Flat-field Refractive Astrograph”,is a refractive equipment with built-in flat field correction. FRA can also be applied in visual observation. So the FRA series is among the few versatile and quality astrophotographic devices in the current astronomy market.

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Product introduction

72mm aperture

400mm focal length

Quadruplet air- spaced APO design

Supporting full frame

0.7x Reducer (optional)

No need for flattener

No need to calculate the backfocus

Retractable lens hood

300mm dovetail plate

multi-functional handle

3" large rack- pinion focuser

1:10 fine adjustment

Various adapter

So the FRA series is among the few versatile and quality astrophotographic devices in the current astronomy market.

For easy parameter conversion between different lenses, the first-come of the FRA family features a Petzval-like quintuplet design (two pieces of which are special ED glass) with an aperture of 72mm, a focal length of 400mm and a focal ratio of f/5.6, providing a 44mm image circle.

The FRA400 quintuplet astrograph has adopted modern optical design with a retractable dew shield, a 3" rack-and-gear-based high-precision reducer containing a 360-degree rotator, M68×1 thread, a 2" adapter ring and a 1.25" visual adapter. The reducer is equipped with fine focal adjustment function for more precise calibration in practical observation or sky imaging.

It’s excellent in controlling and possibly avoiding chromatic aberrations. The image quality is also optimized to satisfy various observing or imaging purposes.

It’s worth mentioning that FRA 400/5.6 has a pair of fashionable-looking and multifunctional patented tube rings. Various practical attachments are available on three sides of the tube rings which is really a convenience for practical observation or imaging activities.

The back focus of FRA400 is 140mm, starting from the base of mounting thread on the housing to the focal plane. And users don't need to worry about the calculation of back focus when using FRA400, as long as the object in the objective lens is focused.

The portable and versatile astrograph can go with many potential attachments of other accessories during your observation or sky imaging. It’s definitely your intimate helper for your exploration.
F/5.6 is a relatively fast focal ratio for astrophotographic use, but we further provide an ultra focal reducer to satisfy the special needs of experienced imagers, greatly reducing the practical focal ratio to f/3.9. This inventive combination supports full-frame imaging and can dramatically shorten the exposure time, which is a pioneering design in the astrophotography field.

The inborn mission of Askar FRA400 is to simplify and enhance our customers’ observing and imaging practice, bringing them infinite surprise when safariing the boundless universe.

Specifications

FRA400 Parameters
Aperture size	72mm
Focal length	400mm
Focal ratio	f/5.6
Objective lens	Quintuplet dual ED air-spaced APO
Image circle	44mm
Back focus	140mm (from the end of rotator M68x1 thread)
Overall length	317mm
OTA Weight	2.56kg
Total Weight (Including tube ring&dovetail plate）	2.88kg
Back-end adapter	M68×1 male thread, 2" adapter/1.25" adapter
Accessories	A pair of tube rings, a handle, a dovetail plate, a M68-M48 conical adapter ， an inspection list, a manual