Askar 90mm F/5.6 FRA500 refractor - quintuplet astrograph
Askar 90mm F/5.6 FRA500 refractor - quintuplet astrograph
Askar 90mm F/5.6 FRA500 refractor - quintuplet astrograph
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.
The astrograph wears smooth coating and is evenly finished. The graduation 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. So the FRA500 can piggyback carry finders, guiders or other potential astronomy accessories.
Askar FRA500 comes also with a pair of sought-after tube rings. On the top of the tube rings attached a handle and at the bottom, there is an Askar Losmandy-style dovetail plate. The combination of milk-white main tube and dew shield together 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.
Specification:
Aperture size：90mm
Focal length：500mm
Focal ratio：f/5.6
Objective lens：Quintuplet air-spaced APO (including two ED glass)
Image circle：55mm
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）
Net weight：4.1kg
Gross weight：5.2kg
Rear-end thread type：M86×1
Conical adapter：M48×0.75
Package items：an FRA500 OTA, a pair of tube rings, a handle, an Askar Losmandy dovetail plate, a conical extender, a manual
| Product Status | New |
|---|---|
| Package width | 40 cm |
| Package height | 36 cm |
| Package depth | 58 cm |
| No. of parcels | 1 |
