Askar ACL 200mm F4 Astrographic Wide Field Lens

The Askar ACL200 provides the Astrophotographer with the benefits of the wide field of view offered by a camera lens but without the optical compromise. Traditionally, pure camera lenses, even those from high end manufacturers, highlight various optical aberrations when used for Astrophotography. Simpley put, a camera lens is expected to perform many tasks. It must focus from close up to infinity and perform well at maximum aperture and also stopped down. Ultimately it is a compromise optically but when used terrestrially, these compromises are rarely seen.

However, when imaging a starfield that contains multiple point sources of light, errors such as field curvature, coma, chromatic aberration (false colour) and astigmatism become obvious. As many modern lenses are also autofocus, they can also be extremely difficult to fine focus manually. On top of this there is often a need to use a filter. A traditional interchangable lens has a fixed back focus distance that is intended to match a specific camera manufacturer. Common examples being 44mm for Canon and 46.5mm for Nikon. While some Astronomy specific imaging cameras do allow use of such lenses and accessories such as a filter wheel or off axis guider, it is usually the case that there is just not enough back focus with a camera lens to permit them.

The Askar ACL200 changes all this.

Offering a 200mm focal length with fast F4 maximum aperture, the ACL200's optical design provides an exceptionally well corrected image over the entire 44mm fully iluminated image circle. This is thanks to a simple six element design that features two extra low dispersion elements.

The ACL200 is also a manual focus lens by design and features two seperate focus rings. The fine focus ring permits ultra fine focus.

The lens is designed to provide 55mm of back focus from its M48 mounting point. This offers plenty of room for additional accessories such as a filter wheel or OAG. In addition the rear section of the lens is removable to allow the installation of a standard 2" filter should you only need one type.

Helping further to aid imaging, the ACL200 incorporates a ring clamp with integrated Vixen format dovetail. This features conventional 1/4" threads for mounting onto a conventional tripod, with the dovetail permitting direct mounting onto an astronomy mount.

Like a conventional camera lens, the ACL200 features an aperture ring and can be stopped down to F22. Its optical performance is maintained even for closer focus applications making this a lens well suited to terrestrial landscape photography.

We think the ACL200 is an outstanding wide field lens that provides an additional element to any astrophotographers inventory.

General Specification