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IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
IMPORTANT: Our store is located in Canada. All orders that include products manufactured outside of Canada or USA will be subject to tariffs and duties, regardless of the order value. US customers are responsible for all applicable duties and tariffs, and those will be billed by the carrier, except for the Lacerta upgrade kit, for which we collect them at checkout.
Askar FMA135 135mm f/4.5 APO Lens

Askar FMA135 135mm f/4.5 APO Lens

by Askar
SKU ASK-FMA135
$329.00 - $329.00
$329.00
$329.00 - $329.00
$329.00
Price Match Policy!
  • 135mm Focal Length
  • f/4.5 Focal Ratio
  • 30mm Aperture
  • Sextuplet APO Optical Design
  • 280g Total Weight
1 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Askar FMA135 135mm f/4.5 APO Lens

    The Askar FMA135 combines a 30mm aperture with a 135mm focal length into a fast f/4.5 optical system designed specifically for wide-field astrophotography. Its advanced sextuplet air-spaced APO objective, which includes one ED glass element, is housed in a compact 113mm body that weighs only 280g. The design provides a native M42×0.75 thread for secure camera attachment and includes a 1.25" adapter for use as a visual finder or guidescope.

    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, perfect for guiding main telescopes with focal lengths up to 1000mm. 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 locking helical focuser, M42 camera threads, and integrated filter compatibility.

  • What kind of objects can I image with the Askar FMA135 on a star tracker?

    The Askar FMA135 is ideal for large deep-sky objects and constellations. Its 135mm focal length allows you to capture vast targets like the Andromeda Galaxy (M31), the Orion Nebula (M42) region including the Horsehead Nebula, the North American Nebula (NGC 7000), and the Rho Ophiuchi cloud complex in a single frame.

    Can I use the Askar FMA135 as a guidescope for my 8" f/10 SCT?

    Yes. With a focal length of 135mm, the Askar FMA135 is an excellent guidescope for telescopes with focal lengths up to and beyond 1000mm, including 8" Schmidt-Cassegrains. Simply attach your 1.25" guide camera using the included adapter.

    What camera connection does the Askar FMA135 have?

    The Askar FMA135 has a standard M42×0.75 male thread on the rear. This allows direct, secure connection to most dedicated astronomy cameras and to DSLR or mirrorless cameras via a standard, camera-specific M42 T-ring.

    Is the Askar FMA135 a true apochromatic (APO) telescope?

    Yes. The objective is a triplet design that includes one element of ED (Extra-low Dispersion) glass to provide excellent chromatic aberration correction. The complete optical system is a sextuplet (6-element) design, engineered to deliver color-pure, high-contrast images.

    How do I focus the Askar FMA135?

    Focusing is achieved with a smooth, precise helical focuser integrated into the objective lens assembly. You rotate the forward part of the lens to achieve sharp focus. This mechanism is more robust and stable than typical camera lens focusing systems for astrophotography.

    Can I use standard 1.25" filters with the FMA135?

    Yes, the front of the Askar FMA135 lens barrel is equipped with a female thread designed to accept standard 1.25" astronomy filters. This allows you to easily add light pollution, narrowband, or color filters to your imaging train.

  • Aperture 30mm
    Focal Length 135mm
    Focal Ratio f/4.5
    Objective Design Sextuplet Air-Spaced APO (with one ED glass)
    Overall Length 113mm
    Total Weight 280g (Including tube ring & dovetail plate)
    Imaging Connection M42×0.75 Thread
    Visual/Guiding Connection 1.25" Adapter

    • FMA135 Lens Assembly

      × 1

    • Mounting Tube Ring

      × 1

    • 1.25" Visual Adapter

      × 1

    • Mounting Screws

      × 5

    • Instruction Manual

      × 1

  • Askar 1-Year Warranty