Askar FRA 500/5.6
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.
It’s excellent in controlling and possibly avoiding chromatic aberrations. The image quality is also optimized to satisfy various observing or imaging purposes.Sharpstar Optics introduces Askar FRA500 astrograph, which is the youngest among the well-known FRA- family, to our customers. 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. Besides, its more lightweight and compact than Askar FRA600, which makes it a great choice for out-door observation or astrophotography. 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 may barely detect any blurry star 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. What you need to focus on is just to make your target stay in focus.
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. Wish the Askar FRA500 be a loyal companion alongside your journey of astrophotography.
Objective lens：Quintuplet air-spaced APO (including two ED glass)
Back focus：158mm（from base of M48×0.75 thread on the conical extender to focal plane）
85mm（from base of M86×1 thread on the rotator to focal plane）
Total length：452mm（410mm when the dew shield is contracted）
Rear-end thread type：M86×1
Package items：an FRA500 OTA, a pair of tube rings, a handle, an Askar Losmandy dovetail plate, a conical extender, a manual