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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 M54/M48 Backfocus Adjuster

Askar M54/M48 Backfocus Adjuster

by Askar
SKU ASK-ASKARBA48
$142.00 - $142.00
$142.00
$142.00 - $142.00
$142.00
Price Match Policy!
  • Provides ±2mm of fine backfocus adjustment
  • Total optical length adjustable from 16mm to 20mm
  • High-precision 0.05mm increments
  • Available with M54 or M48 male camera-side threads
  • CNC machined with laser-etched reference scale
1 in stock
Qualifies for FREE Shipping in CONUS on orders over $350.
  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Askar M54/M48 Backfocus Adjuster

    The Askar M54/M48 Backfocus Adjuster provides a critical ±2mm of fine-tuning for your imaging train, allowing you to dial in spacing between 16mm and 20mm. Each increment on the laser-etched scale corresponds to a 0.05mm adjustment, ensuring you can achieve perfect star shapes across the entire frame. Available in two versions with either M54 or M48 male threads, this CNC-machined adjuster is the solution for eliminating stubborn backfocus errors.

    Eliminate Spacing Errors with 0.05mm Precision Control

    Perfect backfocus is non-negotiable for achieving sharp stars corner-to-corner, but tiny errors from filter thicknesses or manufacturing tolerances can compromise your results. This adjuster provides a total of 4mm of travel, adjustable in 0.05mm increments, allowing you to methodically find the exact spacing your flattener or reducer requires. The CNC-machined body includes a clear, printed scale for repeatable settings and two locking screw holes to fix the position once you've achieved perfect focus.

    An M54 Input with 2 Output Options: M54 or M48

    Both versions of the Askar Backfocus Adjuster feature a female M54x0.75 thread on the telescope side, making them compatible with a wide range of modern correctors. The choice depends on your camera-side connection. Select the M54 male thread version for full-frame cameras and native M54 accessories, or the M48 male thread version to connect to the common 2-inch filter thread standard found on most dedicated astronomy cameras and filter wheels.

  • How do I use the Askar Backfocus Adjuster to find the correct spacing?

    Start with your theoretically correct backfocus distance, accounting for the adjuster's minimum 16mm length. Take a test image and examine the star shapes in the corners. Rotate the adjuster in small, 0.05mm increments and take new test images until the corner stars are perfectly round. Once set, use the two fixing screws to lock the position.

    Which version of the Askar Backfocus Adjuster do I need?

    Both versions accept an M54x0.75 female thread from your telescope or corrector. The choice depends on the next item in your imaging train:

    • M54 Version: Choose this if your camera, OAG, or filter wheel has female M54 threads.
    • M48 Version: Choose this if your camera or filter wheel uses the standard male M48 (2-inch filter) thread.

    My flattener needs 55mm of backfocus, but my train is 53.5mm. Can the Askar Adjuster fix this?

    No, the Askar Backfocus Adjuster cannot fill a gap that large on its own. Its adjustment range is 16mm to 20mm. You would first need to add extension tubes to get close to the required 55mm, and then use the adjuster to fine-tune the final millimeter or two with its ±2mm range.

    How do I lock the position on the Askar Backfocus Adjuster?

    The adjuster features two holes for fixing screws. Once you have rotated the barrel to the desired backfocus distance, you can insert and tighten small screws (not included) into these holes to prevent any further rotation, securing your setting for the rest of your imaging session.

    Will the Askar M54 Adjuster help with elongated stars on my full-frame camera when imaging M31?

    Yes, most likely. Elongated stars in the corners of a full-frame sensor, especially on a large target like the Andromeda Galaxy (M31), are a classic sign of incorrect backfocus. The Askar M54 adjuster is ideal for this, allowing you to make tiny, precise changes to the spacing until those corner stars become sharp and round.

    What is the minimum optical path length of the Askar Backfocus Adjuster?

    The minimum optical path length added by the adjuster is 16mm when it is fully retracted. It can be extended up to a maximum of 20mm.

  • Front Thread (Telescope Interface) M54x0.75 Female
    Rear Thread (Camera Interface) M54x0.75 Male or M48x0.75 Male (model dependent)
    Nominal Thickness 18mm
    Adjustment Range ±2mm
    Total Optical Path 16mm - 20mm
    Adjustment Precision 0.05mm per increment
    Construction CNC Machined Aluminum
    Locking Mechanism 2x Fixing Screw Holes
  • Askar 1-Year Warranty