Askar FMA135 135mm f/4.5 APO Lens

Sextuplet f/4.5 APO Optics: 6-Element Flat-Field Design

Unlike standard telephoto lenses or simple refractors, the FMA135 is a dedicated astrograph with an integrated 6-element optical design. This consists of a three-element (triplet) objective lens and a three-element flattener, working in concert to deliver sharp, color-pure stars across a wide, flat field suitable for modern sensors.

The inclusion of one ED (Extra-low Dispersion) glass element in the objective significantly suppresses chromatic aberration, eliminating the distracting blue or purple halos around bright stars. The native f/4.5 focal ratio allows you to capture faint details in large nebulae and star fields with significantly shorter exposure times compared to slower optical systems.

135mm Wide-Field Astrophotography: From Nebulae to Comets

With its 135mm focal length, the FMA135 is perfectly suited for capturing some of the sky's largest and most impressive targets. Entire constellations, the vast dust lanes of the Milky Way, the full expanse of the Andromeda Galaxy (M31), or the North American Nebula (NGC 7000) can be framed with room to spare, especially on an APS-C sensor.

• Flat Field Imaging: The integrated flattener ensures that stars remain tight, round points from the center to the corners of your image, a critical feature many standard camera lenses lack.
• Secure Connections: A rear M42×0.75 male thread provides a rigid, threaded connection to your astronomy camera or DSLR T-ring, preventing tilt or flexure during long exposures.
• Filter Ready: The front of the lens features a standard 1.25" filter thread, allowing you to use light pollution or nebula filters to enhance your images directly at the objective.

A 280g Multi-Role Instrument: Astrograph, Guider, and Telephoto Lens

Weighing only 280g with its mounting ring, the FMA135 is an exceptionally versatile instrument that excels in multiple roles. Its minimal weight makes it an ideal imaging optic for small, portable star trackers where every gram counts.

Using the included 1.25" adapter, the FMA135 transforms into a high-quality guidescope with a 135mm focal length. It can also serve as a premium straight-through finderscope with a low-power 1.25" eyepiece. For terrestrial photographers, it functions as a compact, manual-focus 135mm telephoto lens with outstanding optical correction.

FMA135 vs. Camera Lenses: An Astro-Specific Advantage

While a high-end 135mm camera lens might offer a faster f-ratio on paper, the FMA135 holds a distinct advantage for astrophotography. Camera lenses are often designed for daytime subjects and must be stopped down to f/2.8 or f/4 to correct for coma and astigmatism that distort stars at the edge of the frame, negating their speed advantage.

• Competitor's Edge: Premium 135mm camera lenses can be faster, some reaching f/1.8 or f/2.0, allowing for more light gathering in a single exposure if optical compromises are acceptable.
• Askar's Advantage: The FMA135 is optimized for a flat, color-corrected field at its native f/4.5. It delivers superior star shapes to the edge of the frame without being stopped down and features astronomy-specific mechanics like a threaded focuser with a setting thread to hold focus, M42 camera threads, and integrated filter compatibility.