Astronomy Specialist





Optec Gemini 3.75" Low Profile Rotofocuser with adapters for Officina Stellare Pro RC, RiDK and RiFAST telescopes. 

Optec engineers have developed a completely new concept for combining telescope focus and camera rotation functions into a single robust, yet compact package.  Rather than simply adding a rotator onto the end of a focuser drawtube, Gemini was designed from inception with a rotating drawtube providing superior strength and rigidity for heavy camera payloads. 

Featuring four lead-screws and four linear bearings, Gemini can easily handle 10kg (22lbs) payload packages without flexure.  Full 360-degree rotation is a built-in function of the Gemini with a full 1/2" of linear travel.  At the center of travel, Gemini measures a mere 2.45" in thickness. 

To maintain a flat, rigid base for heavy camera packages, Gemini's shell consists of two parallel plates machined from MIC-6 tool plate providing flatness within 0.001" (25 microns).  Seven precise stand-off spacers maintain the 2.2" separation of these plates.  The rotating drawtube is moved linearly with 1/2" of total travel using a premium timing belt driven by a high torque stepper motor. 

The entire package is accented with a beautiful carbon fiber wrap.  Dual RJ45 connectors provide connection to the Gemini Control hub.  The independent rotating drawtube is supported by a custom X-cage bearing system supported by large, 6mm chrome ball bearings. 


Clear aperture
95 mm (3.75")
Focuser - 0.11 μ per step, Rotator - 600 steps per degree
Backfocus usage
55.9 mm - 68.6 mm (2.2" - 2.7")
Payload capacity
10 kg (22lbs)
Focuser travel
12.7 mm (0.5")
2.9 kg
239 mm x 187 mm x 55.9 mm
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