About this product
Model: askar_fra500
Part Number: FRA500
Optical Bench Test
All Askar telescopes are tested in the UK on an optical bench.
This ensures you can be confident your telescope will, from the outset, have well-figured optics, negligible false colour and spherical aberration, and no astigmatism (the bane of any optical system!). Star shapes will be round, not triangular, oval or egg-shaped!
The Askar FRA500 with quintuplet (3+2 lenses) air-spaced, fully multicoated Petzval optics.
The front lens group consists of three lenses, including two pieces of ED glass, for excellent correction of aberrations. The rear group is composed of two air-spaced lenses.
Together, they provide a sharp wide, 55mm imaging circle - much larger than the standard 44mm full-frame image circle - that easily covers sensor sizes up to full-frame.
You don't need to calculate back-focus distance or rummage around for a spacer.
The heavy-duty 3.5" focuser has a 1:10 dual-speed mechanism that provides precise focus adjustment.
It is supplied with high-quality tube rings, a carry handle, and a sturdy Losmandy-type mounting plate.
Specifications
Aperture size：90mm
Focal length：500mm
Focal ratio：f/5.6
Objective lens： Quintuplet air-spaced APO (including two ED glasses)
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
What's in the box
- FRA500 Optical Tube
- Tube Rings
- Carry Handle
- Losmandy Compatible Mounting Plate
- Conical M48 Camera Adaptor
- Instruction Manual
Customer reviews
| Average Rating (1 Review): | |
18 December 2022 | Paul
Usual first class deleivery from FLO, arrived with a sticker saying may contain snow, which duly arrived, however so did clear skies. The scope is well made and very easy to set up. Aattaching my ASI183mc pro and eaf was very straight forward, no back focus to worry about. Stars seem to be pin sharp across my images.
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