Starlight Instruments Feather Touch 2.5" R&P Focuser

Purpose-Built for Heavy Imaging Payloads

A Feather Touch Focuser is an absolute must for CCD imaging and astrophotography, in addition to making visual use a joy. The 2.5" model carries 13-15 pounds, so a camera, filter wheel and other accessories can hang from the drawtube within that figure, and threaded end caps give a secure connection for reducers and cameras.

Helical Rack and Pinion: A 13-15 Pound Non-Slip System

At the core of the focuser's strength is its helical rack and pinion drive. This system uses geared teeth to move the drawtube, with a lifting capacity of 13-15 pounds. The helical rack and pinion gives smoother operation, increased carry loads and virtually zero backlash.

The 10:1 Planetary Reduction Assembly

Achieving critical focus is enabled by a friction-based planetary reduction assembly, translating approximately ten rotations of the gold fine-focus knob into one rotation of the coarse knobs. This 10:1 ratio provides the granular control necessary to nail focus on high-resolution planetary targets or with fast optical systems. The assembly sits in the pinion assembly with the brake and pinion shaft, uses stainless steel ball bearings in a brass cage and a tool steel reduction pin, and is lubricated during assembly; it needs no further lubrication.

360° Body Rotation for Perfect Composition

The focuser body rotates a full 360 degrees within its telescope-specific tube adapter, a critical feature for imaging. This allows you to orient your camera to perfectly frame elongated targets like the Andromeda Galaxy (M31) or the Veil Nebula (NGC 6960) without rotating the camera itself. Once positioned, three nylon-tipped gold thumbscrews lock the focuser in the PTFE-lined adapter. For large asymmetrical loads such as heavy motor drives, Starlight offers stainless steel tipped thumbscrews.

Modular Design: Adapters and End Caps

The Feather Touch focuser is a modular system, allowing you to adapt it to a wide range of telescopes and accessories. The focuser body is sold separately from the two key connection pieces:

• Tube Adapter: A telescope-specific adapter ring connects the focuser body to your telescope's optical tube. Options include the A25-2003-1 standard adapter ring (M95x1) and telescope-specific rings, for example Meade 10/12/14" SCT, Celestron C11/C14, Vixen VC200L/VMC200L, AT6/8" RC and William Optics Megrez 80/90, Stellarvue and TMB refractors; which rings are offered depends on the travel version.
• End Cap: An interchangeable end cap threads onto the drawtube, providing the connection for your visual or imaging equipment. Options include the EC25-2005-1 2.0" compression ring end cap and end caps for the Vixen focal reducer, M68x1 female thread and A/P female thread.

Drawtube Engineering: A Millimeter Scale and Baffled Interior

Every detail of the drawtube is optimized for imaging. A millimeter scale is engraved on the side, allowing you to return to precise focus positions quickly when switching between filters or accessories. The interior of the drawtube features glare-resistant black baffling to absorb stray light, maximizing image contrast. Tipped stainless steel set screws are used in the end cap to hold your accessories securely without marring their barrels.

User Adjustments: Brake, Tension, and Collimation Control

You have full control over the focuser's feel and alignment. A brake thumbscrew on the underside of the pinion assembly locks the drawtube; minor fine focus adjustments are still possible, but prolonged use with the brake engaged can wear the brake component prematurely. Drawtube tension is set with the tension nut and a 3/16 hex key (keep at least light tension to prevent drawtube tilt and image shift), while most end caps have three set screws for collimation: loosen them with a 1/16 hex key, unscrew the end cap about 1/4 turn, adjust the tilt and tighten.

Motorization Path: Ready for HSM and PDMS Motor Upgrades

The Feather Touch 2.5" focuser is designed for seamless integration with Starlight Instruments' motorization systems (sold separately). The focus knobs come off with a 1/16 hex key to install a motor. The HSM30 fits any 2.5" Feather Touch focuser, and the PDMS includes a version for 2.5" Feather Touch focusers. A Starlight controller (Focuser Boss II or EFS) runs the motor through ASCOM; the EFS adds temperature compensation.

Build & Materials: USA-Made with #8-32 UNC Mounts

Starlight designs, machines, anodizes and assembles its focusers in-house in Columbia City, Indiana. It is constructed from hardened stainless steel, steel and anodized aluminum. The focuser housing includes two sets of #8-32 UNC threaded holes, fitted with filler screws, for a finderscope base and bracket (sold separately); with third-party bases, use screws that are not too long or they can damage the drawtube.

Installation: A Simple, Secure Two-Part Process

Installation is straightforward. First, loosen the three gold thumbscrews and lift the focuser out of the tube adapter. After removing the stock focuser, attach the adapter to the telescope: in most cases it screws in place, but on some telescopes (such as carbon fiber tubes) it is secured with screws. The Feather Touch focuser body is then inserted into the installed adapter, rotated to the desired orientation, and locked in place with the three gold thumbscrews. Then collimate with the end cap screws if necessary.

Rack & Pinion vs. Crayford: Why Positive Engagement Matters

A Crayford focuser moves the drawtube by friction. Starlight's 2" Crayford is rated at 8-10 pounds, while its 2.5" and 3.0" rack and pinion focusers are rated at 13-15 pounds.

The Feather Touch R&P uses a helical rack on the underside of the drawtube, driven by the pinion, which gives increased carry loads and virtually zero backlash.

Draw Tube Travel Options: 1.5", 2.5", and 3.5" Variants

This focuser is available in three different drawtube travel lengths to suit various telescope designs and imaging configurations. The required travel depends on your optical system's back focus requirements and the accessories you intend to use. The available options are 1.5" (38.1 mm), 2.5" (63.5 mm), and 3.5" (88.9 mm), by variant.