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Optec Gemini Low-Profile Focusing Rotator System

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3.50 kg
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including VAT 20.00 % ( £601.50 )

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 10-kg. (22-lbs.) 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. 


Package includes Gemini controller, Hand Controller, power supply, cables and Pelican type case. Stock item #19830 OPTEC-4300 to DSI 3.5x24tpi threaded adapter is now included for the camera side mount. Optec-DSI 3.5x24tpi threaded extensions available separately.

Robust Compact Design

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. 

Temperature Compensation:

Like all Optec focuser products, Gemini includes a remote temperature probe for automatic temperature compensation.  Simply attach the temperature probe anywhere in the linear response zone of your OTA (usually the tube or truss assembly) and Gemini will automatically keep the camera package in sharp focus. The Gemini Commander software provides a convenient wizard to help determine your telescope's TC or temperature coefficient.

Support for Multiple Telescopes

Featuring identical OPTEC-4300 mechanical interfaces front and back, the Gemini can be easily fitted to most any large telescope OTA.  Recessed oval point setscrews provide three-point direct contact with the heavy wall OPTEC-4300 dovetail mount.  Gemini's clear aperture of 3.75" is maintained through each adapter, passing even large light cones through to the camera image plane without vignetting.

On the camera side, a typical configuration might include a 4300 receiver for the Optec-DSI 3.5 High Performance spacer sets configurable to 1/4" increments when additional spacing is needed. 

Currently designed telescope adapters include support for the AG Optical iDK's, Ceravolo Optical Systems Astrographs, Meade and Celestron 10-inch and larger class SCT, and Plane Wave Secure-Fit. 

Multiple Ways to Connect:

The Gemini Control hub acts as the central controller to link both focuser and rotator to any control PC. The hub includes communication ports for Serial and USB (using Optec's USB/Serial cable) and wired Ethernet Network protocols as standard. An optional WiFi board and antenna can be added and installed at any time.  Focuser and Rotator ports are available at the top of the Gemini hub with 12VDC Power, Network, optional Hand Control, and Serial connection ports available at the bottom.

Complete Package includes Hand Controller:

Each Gemini package comes complete with everything needed to connect.  The Gemini package includes our updated Gemini Hand Controller which allows jiggle-free manual control while at the telescope. Now featuring a rotary encoder and integrated thumb knob, exact focus adjustments can be made without touching the telescope or focuser.

 Our precision external temperature probe, power supply, and ultra-flat Ethernet cables round out a complete integrated package.

Gemini Commander Software

Visit the Gemini Software Downloads Page for the latest updates and ASCOM driver, Gemini  Commander control software and additional resources.

ASCOM StandardsGemini Commander creates an ASCOM Local Server or hub to allow multiple clients access for communication and control of the attached focusers.  By using the local server model, Gemini offers an easily configurable user experience for all Windows ASCOM programs.

Specifications for Gemini and Controller:

Focusing Rotator Physical Specifications:

  • Clear Aperture:    3.75" (95mm)
  • Back-Focus Usage:    2.2" to 2.7" (55.9 to 68.6mm)
  • Focuser Travel:    0.5" (12.7mm)
  • Focuser Resolution:    0.11 microns per step
  • Rotator Resolution:    600 steps per degree
  • Minimum Overall Thickness:    2.2" (55.9mm) [Full IN position]
  • Dimensions:   9.4" x 7.4" (239mm x 187mm)
  • Weight:    6 lb. 6 oz. (2.9 kg)

Gemini Controller Hub Specifications:

Controller Hub Specifications:

  • Length:  5.1" (130mm)
  • Width:  3.2" (81mm)
  • Height: 1.0" (27mm)
  • Weight: 10 oz. (285 g)
  • Mounting Holes:   Four 4-40 x 1/8" depth (reverse side)
  • Case Material:  6061 aluminum, anodized black.

Gemini Hub Port Connections:

  • Focuser:    RJ45 socket for standard Cat-5e/Cat-6 cable to Focuser port,
  • Rotator:    RJ45 socket for standard Cat-5e/Cat-6 cable to Rotator port,
  • Power:    12VDC input, 2.5 x 5.5mm plug, center pin positive,
  • Network:    Standard RJ45 Ethernet socket,
  • Hand Controller:    RJ22 socket for standard telephone handset cord,
  • Serial:    RJ12 socket for Optec USB/Serial cable (included),
  • Wireless:   802.11 WiFi option (coming soon).

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