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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.
Starlight Instruments Feather Touch 3.5" R&P Focuser

Starlight Instruments Feather Touch 3.5" R&P Focuser

by Starlight Instruments
SKU SI-FTF3515B-A
$960.00 - $980.00
$960.00
$960.00 - $980.00
$960.00
Price Match Policy!
  • 3.5-inch rack and pinion focuser for large telescopes
  • Supports heavy imaging payloads of 18-20 pounds
  • Dual-speed 10:1 reduction ratio for precise fine focusing
  • 360-degree rotating locking collar for easy framing
  • Available in 1.375" and 4.5" draw tube travel options
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  • Description
  • FAQ
  • Specifications
  • In the Box
  • Downloads
  • Warranty

  • Starlight Instruments Feather Touch 3.5" R&P Focuser

    The Starlight Instruments Feather Touch 3.5" R&P Focuser is engineered to carry imaging payloads of 18-20 pounds without flexure, making it the definitive focusing solution for large RC and Dobsonian telescopes. Its robust rack and pinion drive mechanism, combined with a precise 10:1 dual-speed reduction, eliminates image shift and allows for repeatable, critical focus adjustments. Weighing 5.216 pounds, this American-made focuser features a 360-degree locking collar for effortless composition and is built from hardened stainless steel and anodized aluminum for a lifetime of use.

    Helical Rack & Pinion Drive: A Certified 18-20 Pound Capacity

    Designed specifically for heavy instrument packages, this focuser's helical rack and pinion drive provides a certified lifting capacity of 18-20 pounds. Unlike Crayford designs that can slip under heavy loads, the geared mechanism ensures your large-format camera, filter wheel, and off-axis guider remain perfectly stationary at any orientation. The construction from hardened stainless steel and aluminum guarantees rigidity, preventing tilt and flexure that can ruin long exposures.

    10:1 Dual-Speed Reduction: Precision Control Without Image Shift

    Achieving critical focus is non-negotiable for high-resolution imaging. The Feather Touch focuser employs a celebrated 10:1 planetary reduction assembly, allowing for exceptionally fine adjustments with zero backlash. The millimeter scale on the draw tube provides a reliable reference for repeatable focus positions between sessions or filters. This level of control lets you snap stars to perfect points without the coarse jumps or image movement common in lesser focusers.

    360° Locking Collar: Frame Your Target Without Compromise

    The integrated 360-degree locking collar is an essential feature for imagers. It allows you to rotate your entire imaging train to perfectly frame your target—from the faint spiral arms of the Andromeda Galaxy (M31) to complex mosaics of the Cygnus Loop—without having to physically rotate the camera in its adapter. Once your composition is set, the collar locks down securely, maintaining perfect alignment. Furthermore, the end cap provides collimation adjustment via three set screws, ensuring your optical train is perfectly orthogonal to the focal plane.

    Engineered for Large Scopes: 1.375" and 4.5" Travel Options

    This focuser is available with either 1.375 inches or 4.5 inches of draw tube travel to accommodate a wide range of optical configurations on large RC and Dobsonian scopes. The shorter travel is ideal for systems with minimal back-focus requirements, while the longer travel provides flexibility for complex imaging trains. This modularity, combined with a selection of custom tube adapters and end caps (sold separately), ensures a perfect, rigid connection to your specific telescope.

    Feather Touch 3.5" vs. Stock Focusers: The Imaging Upgrade

    For owners of large Ritchey-Chrétien or Dobsonian telescopes, upgrading from a stock focuser to the Feather Touch 3.5" is one of the most significant improvements you can make for astrophotography. It directly addresses the two most common points of failure in factory-standard focusers.

    • Eliminates Mirror Shift: On SCTs and RCs, the Feather Touch replaces the imprecise mirror-moving mechanism, providing a fixed, external draw tube that completely eliminates image shift during focusing.
    • Prevents Flexure and Slippage: Compared to stock Crayford focusers on Dobsonians, the 18-20 pound capacity and rack and pinion drive of the Feather Touch prevent the draw tube from sagging or slipping under the weight of a heavy camera and accessories.

  • What is the main advantage of the Feather Touch 3.5" R&P over a Crayford focuser for imaging?

    The primary advantage is its 18-20 pound lifting capacity and positive drive mechanism. A rack and pinion (R&P) system uses gears that cannot slip, unlike a friction-based Crayford which can lose grip under heavy loads or when the telescope is pointed near the zenith. This makes the R&P design essential for heavy, modern imaging trains.

    How do I choose between the 1.375" and 4.5" draw tube travel options for the Feather Touch 3.5" Focuser?

    The choice depends on your telescope's back focus and your imaging setup. The 1.375" travel option is best for systems where you have limited inward focuser travel or a fixed imaging train. The 4.5" travel option provides greater flexibility for accommodating different accessories like reducers, off-axis guiders, or visual eyepieces that may require significantly different focus points.

    Can the Feather Touch 3.5" focuser be automated for astrophotography?

    Yes. Starlight Instruments offers several motorization options, such as the Handy Stepper Motor (HSM) or Posi Drive Motor System (PDMS), which are designed to integrate seamlessly with the Feather Touch 3.5" focuser. These systems, combined with control hubs like the Focuser Boss II, allow for fully automated, temperature-compensated focusing controlled via ASCOM or other standard software.

    I have a large Dobsonian and want to use a heavy binoviewer. Is the Feather Touch 3.5" sufficient?

    Absolutely. With a lifting capacity of 18-20 pounds, the Feather Touch 3.5" can easily handle even the heaviest binoviewers paired with two large eyepieces. The rack and pinion drive and internal brake ensure that the focuser will not sag or slip, maintaining perfect collimation and focus regardless of where the telescope is pointed.

    Will the Feather Touch 3.5" focuser eliminate mirror flop on my large RC telescope when imaging faint galaxies like NGC 7331?

    Yes. By bypassing the telescope's internal mirror-focusing mechanism, the Feather Touch 3.5" completely eliminates the problem of mirror flop or image shift. This is critical for long-exposure astrophotography of faint targets like the Deer Lick Group (NGC 7331), as it ensures the field remains perfectly stable while you make fine focus adjustments.

    What do I need besides the focuser itself to install the Feather Touch 3.5" on my telescope?

    The Feather Touch 3.5" focuser is sold as a modular component. To install it, you will need to purchase a tube adapter ring specific to your telescope model and an end cap for the draw tube (e.g., a 2" compression ring). These items are sold separately to ensure a perfect fit for your specific instrument.

  • Lifting Capacity 18-20 pounds
    Draw Tube Travel 1.375″ / 34.93mm (4.5" option available)
    Draw Tube Drive Rack & Pinion
    Reduction Ratio 10:1
    Rotation 360 degrees with locking collar
    Focuser Weight 5.216 pounds (with standard adapter and end cap)
    Racked In Dimension 5.236″ from mounting face
    Racked Out Dimension 6.625″ from mounting face (with 1.375" travel)
    Draw Tube Scale Millimeter
    End Cap Collimation 3 set screws
    Construction Hardened stainless steel, steel, anodized aluminum
    Internal Baffling Glare-resistant black
    Focus Knobs Dual speed coarse/fine
    Accessory Threads 5.125"x24 Female (Locking Collar), 4 3/32"x24TPI (Draw Tube)
    Finderscope Mounting 8-32 threaded holes
    Compatibility Large RC/Dob Scopes
    Country of Origin USA

  • This product is sold as the focuser body only. Tube adapters, end caps, and other accessories must be selected and purchased separately to match your specific telescope.

  • Starlight Instruments 2-Year Warranty