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Optec Gemini Focusing Rotator

Optec Gemini Focusing Rotator

Starting Price: $3,595.00
Price as Configured: $3,595.00
Brand: Optec / SKU: OP-19750
Optec’s Gemini redefines what a focuser and rotator can be. Instead of attaching a rotator to the end of a drawtube, Gemini was engineered from the start as a fully integrated rotating focuser. The result: a compact, ultra-rigid system built to carry today’s heaviest imaging setups with ease.

With four lead screws and four linear bearings, Gemini delivers unmatched stability, handling payloads up to 10 kg (22 lbs.) without flexure. Enjoy 360° continuous camera rotation and ½ inch of precision linear travel—all in a package just 2.45 inches thick at mid-travel. Powerful, precise, and purpose-built for astrophotographers.

Features:

Payload Capacity: up to 10 kg (22 lbs.)

Design: Four lead screws with four linear bearings

Rotation: 360° continuous

Linear Travel: 0.5 in. (12.7 mm)

Profile Thickness: 2.45 in. at center of travel

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The Optec Universal Mounting Bracket screws directly to the back of the FocusLynx Control Hub back and allows easy attachment to most any mount. 

  • Material:  6061 aluminum, anodized black
  • Length:  4.9" (124mm)
  • Width:  4.7" (120mm)
  • Thickness: 0.1" (2.5mm)
  • Weight: 1.8 oz (50 g)
  • Mounting Holes:  Clearance for 1/4-20
  • Connection to FocusLynx:  Four 4-40 flathead screws (included)
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OP-19755 - Optec WiFi 802.11b/g Wireless Network Board
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WiFi board with 802.11b/g connectivity to local wireless networks. Works with both FocusLynx and Gemini control boards.

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OP-19691 - Optec Universal Mounting Bracket for Focus Lynx Control Hub
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OP-19691 - Optec Universal Mounting Bracket for Focus Lynx Control Hub
About This Product

The Optec Universal Mounting Bracket screws directly to the back of the FocusLynx Control Hub back and allows easy attachment to most any mount. 

  • Material:  6061 aluminum, anodized black
  • Length:  4.9" (124mm)
  • Width:  4.7" (120mm)
  • Thickness: 0.1" (2.5mm)
  • Weight: 1.8 oz (50 g)
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OP-19755 - Optec WiFi 802.11b/g Wireless Network Board
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OP-19755 - Optec WiFi 802.11b/g Wireless Network Board
About This Product
WiFi board with 802.11b/g connectivity to local wireless networks. Works with both FocusLynx and Gemini control boards.

Compatible with:
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OP-19752 - Optec Gemini Hand Control
OP-19752 - Optec Gemini Hand Control
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OP-19752 - Optec Gemini Hand Control
About This Product
The #19752 Gemini Hand Control provides an easy, vibration-free method of focusing the telescope when using the Gemini Focusing Rotator.  Featuring IN and OUT buttons, a 2-line display, and a rotary Fine Focus Knob, this Hand Control is a "must-have" option for any Gemini system where the operator may be present at the telescope. 

The Gemini Hand Control includes an  electronic Fine Focus Knob for greater control and tactile feedback while using eyepieces at the telescope.  An embedded rotary encoder switch allows one-hand fine focus control while using an eyepiece.  No need to move your eye away from the eyepiece - with this improvement the Gemini hand control provides simple, intuitive and precise control of the focus motor.

The Gemini Hand Control plugs into the  Hand Controller port on the bottom of the Gemini Control Hub using the included telephone handset cord.

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OP-17680 - Optec Remote IN/OUT Keypad for TCF or Gemini
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OP-17870 - Optec-3600 to Optec-4300 Expansion Ring
About This Product
The 3600 to 4300 Expansion Ring allows owners of any OPTEC-3600 telescope adapter to easily expand the male dovetail out to 4.3-inches matching the OPTEC-4300 spec.

Inside Diameter: 3.6" (91mm)
Outside Diameter: 4.95" (126mm)
Overall Height: 0.42" (10.7mm)
Clear Aperture: 3.6" (91mm)
Weight: 3.4 oz (100 g)
Back-Focus Usage: 0.1" (2.5mm)

Camera-Side:
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  • Gemini Focusing Rotator.
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OP-19830 - Optec-4300 to Female Optec DSI 3.5"
OP-19830 - Optec-4300 to Female Optec DSI 3.5"
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OP-19830 - Optec-4300 to Female Optec DSI 3.5"
About This Product
The #19830 OPTEC-4300 to female Optec/DSI 3.5" threaded receiver allows any combination of our DSI 3.5-inch spacers to be easily installed on the camera side of the Gemini Focusing Rotator.

Inside Diameter: 3.5" DSI Thread
Outside Diameter: 4.95" (125.7mm)
Overall Height: 0.42" (10.7mm)
Clear Aperture: 3.46" (88mm)
Weight: 3.8 oz (110 g)
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Compatible with:
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OP-19831 - Optec-4300 to Male Optec-DSI 3.5" x 24tpi
OP-19831 - Optec-4300 to Male Optec-DSI 3.5" x 24tpi
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OP-19831 - Optec-4300 to Male Optec-DSI 3.5" x 24tpi
About This Product
The #19831 Male Optec/DSI 3.5" to OPTEC-4300 male dovetail fits the telescope side receiver of the Gemini and allows any combination of our DSI 3.5-inch spacers to be easily installed on the telescope side of the Focusing Rotator.

Inside Diameter: 3.165" (80.4mm)
Outside Diameter: 4.95" (125.7mm)
Overall Height: 0.83" (21.0mm)
Clear Aperture: 3.165" (80.4mm)
Weight: 4.8 oz (135 g)
Back-Focus Usage: 0.1" (2.5mm)

Compatible with:
  • Optec/DSI 3.5" Threaded Spacers.
  • Gemini Focusing Rotator (typically used on telescope side).
OP-19839 - Optec-4300 Extension Adapter, 25mm Length
OP-19839 - Optec-4300 Extension Adapter, 25mm Length
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OP-19839 - Optec-4300 Extension Adapter, 25mm Length
About This Product
The OPTEC-4300 25mm Extension Ring provides approximately 1-inch of extension for any OPTEC-4300 telescope adapter. Ideal for telescopes where the Gemini Focusing Rotator may need to pushed out and away from the OTA to provide clearance for cooling fans or when a little extension is required to reach optimal focus.

Inside Diameter: 3.9" (99mm)
Outside Diameter: 4.95" (126mm)
Overall Height: 1.30" (33.2mm)
Clear Aperture: 3.9" (99mm)
Weight: 8.8 oz (250 g)
Back-Focus Usage: 0.984" (25mm)

Compatible with:
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OP-19843 - Optec-4300 to Takahashi Epsilon 180
OP-19843 - Optec-4300 to Takahashi Epsilon 180
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OP-19843 - Optec-4300 to Takahashi Epsilon 180
About This Product
The #19843 adapter replaces the Captain's Wheel focuser of Takahashi's Epsilon Astrographs and allows attachment of the Optec Gemini Focusing-Rotator.

Optec now offers a complete focusing rotator option for owners of Takahashi's legendary Epsilon 180 Astrograph. Gemini's Low-Profile Focusing Rotator, coupled with the #19843 and #19844 adapters provides a drop-in replacement for the native E180 focuser.

Inside Diameter: 3.90" (99mm)
Outside Diameter: 4.80" (122mm)
Overall Height: .64" (16.2mm)
Clear Aperture: 3.90" (99mm)
Weight: 3.6 oz (100 g)
Back-Focus Usage: 0.25" (6.35mm)
Telescope Side Connection: M108 Takahashi female thread
Camera Side Connection: OPTEC-4300 male dovetail

Telescope Compatibility:
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Device Compatibility:
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TCF-Lynx3 Gen2 focuser (mfg. after Jan. 2018),
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OP-19844 - Optec-4300 to Takahashi Epsilon 180 Field Flattener
OP-19844 - Optec-4300 to Takahashi Epsilon 180 Field Flattener
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OP-19844 - Optec-4300 to Takahashi Epsilon 180 Field Flattener
About This Product
Optec now offers a complete focusing rotator option for owners of Takahashi's legendary Epsilon 180 Astrograph. Gemini's Low-Profile Focusing Rotator, coupled with the #19843 and #19844 adapters provides a drop-in replacement for the native E180 focuser.

The #19844 adapter allows owners of the Takahashi Epsilon Astrograph to insert their field flattener directly into the Gemini. Proper spacing is maintained for the E180 Field Flattener with a recessed M68 thread. First screw the Field-Flattener into the #19844 adapter, then secure the FF/Adapter assembly into the Gemini drawtube. This sets the FF at the design distance from the primary mirror and maintains the 56mm back-focus available to the camera sensor.

Inside Diameter: M68x0.75mm thread
Outside Diameter: 4.80" (122mm)
Overall Height: 0.62" (15.7mm)
Clear Aperture: 2.66" (67.6mm)
Weight: 6.8 oz (190 g)
Back-Focus Usage: 0.25" (6.35mm)
Telescope Side Connection: OPTEC-4300 male dovetail
Camera Side Connection: M68 x 0.75mm female thread

Device Compatibility:
Gemini Focusing Rotator.

Camera Side Compatibility:
Takahashi Epsilon 180 field-flattener.


OP-19846 - Optec-4300 to Internal 3" Clamp
OP-19846 - Optec-4300 to Internal 3" Clamp
$165.00
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OP-19846 - Optec-4300 to Internal 3" Clamp
About This Product
OPTEC-4300 to internal 3-inch clamp to allowstight fit of Paracorr, Wynne Correctors, and other 3-inch optics for the Gemini Focusing Rotator. Adjustable placement of lens inside Gemini drawtube allows ideal spacing of corrector / flattener optics to primary mirror. OPTEC-4300 to internal 3-inch clamp to allow tight fit of Paracorr, Wynne Correctors, and other 3-inch optics. Adjustable placement of lens inside Gemini drawtube.

Includes:
3-inch internal clamp assembly with OPTEC-4300 dovetail,
9/64” ball driver,
5/64” hex key.

QTY:  
Price as Configured: $3,595.00

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Precision Meets Power

Like all Optec focusers, Gemini is equipped with a remote temperature probe for automatic focus compensation. Simply attach the probe anywhere along your OTA’s thermal response zone—typically the tube or truss assembly—and Gemini continuously adjusts focus as temperatures change. The included Gemini Commander software makes setup easy, with a guided wizard that determines your telescope’s exact temperature coefficient.

Engineered for Heavy Imaging Payloads

Gemini’s foundation is built for strength. Its housing is crafted from MIC-6 aluminum tool plate, machined to within 0.001" (25 microns) flatness. Two parallel plates, separated by seven precision spacers, maintain a perfectly rigid 2.2" structure. The rotating drawtube delivers ½ inch of precise linear travel, powered by a premium timing belt and high-torque stepper motor. A custom X-cage bearing system, reinforced with large 6mm chrome ball bearings, ensures smooth and stable rotation—even under heavy loads. Finished with a carbon fiber wrap, Gemini blends performance with elegance.

Flexible Integration

Designed with Optec-4300 mechanical interfaces on both front and back, Gemini adapts seamlessly to a wide range of large telescope OTAs. Recessed oval point setscrews provide secure three-point contact with the OPTEC-4300 dovetail mount, while a generous 3.75" clear aperture preserves wide light cones without vignetting.

On the camera side, Gemini now ships with the #19830 OPTEC-4300 to DSI threaded adapter, compatible with Optec’s DSI 3.5" spacers. These allow precise backfocus adjustments in ¼" increments, ensuring exact optical alignment for every imaging train.

Telescope Compatibility

Gemini adapters are available for leading instruments, including:

  • AG Optical iDK series

  • Celestron OTAs

  • Ceravolo Optical Systems Astrographs

  • Meade 16-inch class SCTs

  • PlaneWave Secure-Fit systems

  • Takahashi telescopes

With its combination of rigid construction, smooth motion, and versatile compatibility, Gemini is the ultimate solution for astrophotographers demanding precision and reliability.