Sharpstar Optics introduces Askar FRA500 astrograph, which is the youngest among the well-known FRA- family. Compared with its siblings, the 500mm-focal-length refractor has an aperture size of 90mm (f/5.6), so Askar FRA500 can better fit into the scenarios of deep-sky imaging than Askar FRA400. The FRA500 is more lightweight and compact than Askar FRA600, which makes it a great choice for out-door observation or astrophotography.
The Askar FRA500 has inherited the legacies of superior FRA- series designing. It boasts a quintuplet air-spaced APO optical structure, a “three plus two” Petzval lens combination. The front lens group consists of three lenses (including two pieces of ED glass) for excellent correction of aberrations. The posterior group is composed of two lenses separated by small space which is able to provide fine sharpness across the whole image. You can barely detect blurry stars at the edge of the image. FRA500 supports an image circle of amazing 55mm, much larger than the standard 44mm full-frame image circle. Its special back-focus design frees users from calculating confusing back-focus distance or rummaging around for a proper spacer. All you need to worry about is keeping your target in focus.
The Askar FRA500 is a wonderful mix of pragmatism and aesthetics. The astrograph shows smooth lines and a sound layout of components. From the front, the Askar FRA500 has an impressive dew shield decorated with a classic bright-red bezel ring. The total length of FRA500 is 452mm when the dew shield is stretched out and 410mm when contracted back. At the tail end of the astrograph locates a 3.5" massively-built focuser with dual-speed hand knobs (twin knobs for coarse adjustment and one 1:10 fine adjustment knob), which is of great use in real observation or astrophotography.
Made with a smooth coating for an even finish, the inside of the focuser is quite clear and easily readable. The focuser is tough and solid, and on the left side of it, there is a standard finder base with a silver thumb screw. This allows the FRA500 to carry finders, guiders or other potential astronomy accessories.
The Askar FRA500 comes also with a pair of tube rings. Attached to the top of the tube rings is a handle and at the bottom there is an Askar Losmandy-style dovetail plate. The combination of a milk-white main tube and dew shield, with a high-gloss piano-black focuser makes the optical tube assembly calm and deep which is offset by the bright red decorative ring and tube rings.
The Askar FRA500 is 410mm long and weighs about 4kg, making it quite convenient for users to carry around or mount on an EQ mount. It is particularly suitable for those who frequently engage in long-distance trips or out-door astrophotography.
The Askar FRA500 together with the FRA- family is well received for large aperture, fast speed, delicate focusing system, unique optical design and the subsequently high-quality imaging results. Making the Askar FRA500 a loyal companion throughout your journey of astrophotography.