Gemini Focusing Rotator

#19750 - Gemini Focusing Rotator System

Sky & Telescope Hot Product Award!

The Editors of Sky & Telescope magazine have chosen the Gemini Focusing Rotator as a 2016 Hot Product 

New Design Concept:Gemini Focusing Rotator

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 midpoint, Gemini measures a mere 2.45" or about 62.2mm in thickness. 

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.

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. 

Dual Function Control with Multiple Options

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, the Gemini package now includes our #19830 OPTEC-4300 to DSI threaded adapter.  This part converts the camera side to a receiver for any of our Optec-DSI 3.5 High Performance spacers configurable to 1/4" increments when additional back-focus spacing is needed. 

Currently designed telescope adapters include support for the AG Optical iDK's, Celestron, Ceravolo Optical Systems Astrographs, Meade 16-inch class SCT, Plane Wave Secure-Fit, and Takahashi telescopes.   

Additional adapters available through PreciseParts.

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.

Contact Optec Sales or any of our Dealers for a system specifically configured for your telescope rig or observatory. 

Coming Soon - 802.11 WiFi Option:

Using the ASCOM Local Server model, Optec's Gemini Commander software allows multiple clients to connect simultaneously to the Gemini hub.  Soon to be released embedded webservers in the wired Ethernet and WiFi connections enable Gemini to generate a control interface accessible through any web browser or smartphone. Free Android and iPhone applications search the local network and load the interactive webpages.  Because these pages are generated by the hub itself, once you are connected, there is no further configuration required: just connect to Gemini and enjoy remote wireless focus control with the optional 802.11 WiFi add-on. 

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).
How to Order:

Contact any Optec dealer, call Toll-Free 1-888-488-0381, email, or visit our ecommerce site:

Package includes Gemini Focusing Rotator, Gemini controller hub, 12VC power supply with wall cord, and all cables.  Order telescope mount and options separately.

NOTE:  Delivery for new orders is usually from stock.   Contact Optec Sales to inquire about current delivery. 

Contact Optec Sales for a formal custom package quotation complete with adapters, spacers, and camera fittings.

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