About this product
Part Number: ACL200
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!
New Askar ACL200 200mm f/4 Lens Designed for Astrophotography
The Askar ACL200 200mm f/4 lens is the first of its kind designed specifically for astrophotography in addition to landscape photography.
Very high quality optics in a lightweight easy to use design.
The fast F/4 focal ratio provides short exposure times so can be used with more affordable tracking mounts.
When used for deep-sky astrophotography, the images are clear and sharp with negligible distortion or chromatic aberration. Chromatic halos often seen in images made with regular camera lenses are virtually absent from images made using the Askar ACL200.
Provides flat-field correction suitable for most camera sensor sizes, including 4/3, APS-C and even full-frame!
Perfect for use with DSLR or mirrorless cameras but can also be used with dedicated astrophotography cameras using a M48 camera adapter to achieve the required 55mm back focus distance.
Two focus controls (a coarse adjustment for rough focusing and 1mm micro adjustment for precision focusing) are provided.
The aperture can be manually adjusted from f/4-f/22 so a good choice also for daytime use.
Other features include an integral 360º rotator for convenient framing and a Vixen-style dovetail plate with 3/8" and 1/4" threaded holes (can be fitted directly to most astronomy mounts).
- 50mm Aperture
- f/4 / 200mm focal ratio / length
- High quality six element design that includes two ED elements for excellent colour correction
- 10 piece aperture blades
- Dual-speed manual helical focusing with coarse and 1mm micro focus adjustments
- Closest focusing distance around 3m
- f/4-f/22 manual aperture control
- 82mm front filter thread
- Lockable 360º rotator
- Approximately 135-180mm long / 100mm diameter
- 1.8kg weight
- Integrated 2" filter holder
- Back-end connection: M48x0.75 male thread
- Vixen-style dovetail plate with 3/8" and 1/4" threaded holes (can be fitted directly to most astronomy mounts).
Telescope Field of View Simulator
Integrated 2" Filter Holder
This lens is designed with triplet of six lenses, among which two pieces of ED ultra-low dispersion glass are added, making it better than ordinary lens in reducing chromatic aberration and have clearer image.
What's in the box
- ACL200 body
- Lens shade
- Vixen-style dovetail plate with 3/8" and 1/4" threaded holes
- Soft padded case
- 2" filter Holder (assembled with the Lens)
- Instruction manual
- Quality Control checklist
|Average Rating (1 Review): |
Friday, 3 December 2021 | Neal
I have had my ACL200 since May 2021 and I am amazed that nobody has written a review of this superb lens/scope. So here is one.
When I first looked at buying one I thought that it seemed a bit pricey. Don't be fooled - it's not. My first surprise was to find that the build quality of this lens is amazing and the optical quality backs it up. I have found no sign of chromatic aberration at all, and the shape of all the stars into the corners of an MFT 20mpix sensor is perfect. I can't vouch for a full frame sensor but I suspect it would pass that test as well.
Another surprise is that the focus control is fantastic. I don't normally like helical focusers but this dual system is better than any manual focus system I have used in forty years of photography. It is very smooth and there appears to be no backlash at all with the fine focus ring. Then once locked the focus never seems to alter over a night's photography. Inital focusing is easy using a Bahtinov mask despite, as I understand it, that Bahtinovs are better for longer focal lengths.
So are there any downsides to this lens? Well, I suppose if you twisted my arm I can think of two minor issues. Firstly it is weighty, and not 'lightweight' as they imply. Mine was 2 kgs, which is over three times the weight of my Panasonic 100-300 f5.6 zoom lens. But it is fine with smaller go-to mounts (I have an EQ5 Pro) or an iOptron Skyguider Pro camera mount. Secondly, you do need to take a little care to make sure that the iris is opened fully, i.e at f4. The reason being that if you stop it down even a very small amount then very bright stars will have a funny spiky pattern around them. This isn't a fault but merely the laws of optical physics, and is seen when you process and stretch a stacked image strongly. You don't see it on a single frame as far as I am aware. The vanes of the iris act like multiple short spikes in a similar way to the spider vane spikes of a Newtonian reflector telescope. So it is best to only use the iris for terrestrial photography.
If you want a top quality lens of that focal length, and have the money for it, then why would you pass it by? Very highly recommended by me; a happy FLO customer.
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