Description
If you’re running a larger RC (or similar back end that uses the M117 standard) and you want a focuser that stays put under real imaging weight, this 3" rack-and-pinion upgrade is built for exactly that job. The key advantage of this design is that the drawtube support and the focusing drive are separated—so the tube rides on low-friction bearing surfaces while the gear train provides the movement. The result is a focuser that remains stable with heavy cameras, filter wheels, and reducers without the “give” you can sometimes see in lighter Crayford designs.
Why this focuser is a serious imaging upgrade
Geared drive with high load stability
Instead of relying on friction pressure to hold position, the rack-and-pinion drive provides positive, repeatable movement and strong holding power—useful when you’re hanging a substantial imaging train off the back of the scope.
Dual-speed control (10:1 microfocus)
Fast coarse focusing gets you close, and the 10:1 reduction makes it easy to land on critical focus without overshooting.
Rotation for easy framing
The included adapter assembly supports full rotation so you can square up a camera or reframe without fighting your mount orientation.
Big clear aperture for modern sensors
With a large light path and a 3" class focuser body, it’s designed to play nicer with larger camera formats and fast RC imaging accessories. (Exact clear-aperture figure below.)
Telescope connection
-
Telescope side thread: M117 (via the included connection adapter)
-
Optional plug connection: remove the adapter to reveal a 105 mm plug interface for custom fits/adaptations
Technical parameters
- diameter of drawtube: 3"
- Focusing mechanism: Rack & Pinion
- Lift stroke: 45 mm
- Mounting thread (telescope side): M117x1 (female)
- Output threads: M78x1 (female), M68x1 (female), M74x1 (male)
- adapters included: 2" and 1.25"
- load capacity: up to 6 kg
- weight: 1.64 kg
- compatibility with focusing motors: yes (e.g. ZWO EAF)