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The Losmandy Gemini system is a DC servo motor based GOTO computerised positioning system designed for Losmandy mounts.

The system can be ordered with all new Losmandy mounts, or easily retrofitted by users who already own a mount. The new Gemini system simply replaces the existing stepper drive motors and electronics, with hex keys plus a small pair of pliers being the only tools required to upgrade the drive.

The Gemini system has many features designed to quickly and accurately point the telescope to an object, then track it with even higher precision than the previous digital stepper drive used by Losmandy.

The choice of servo motors gives two main advantages over stepper motor based systems.

• Servo motors run with a continuous smooth rotation, rather than discreet steps as with stepper motors.

• They also have very high torque, even at high slewing speeds.

As a result the Gemini system can deliver up to *10 degrees per second slewing rates, yet still retain motor positional information of around 1/10th of an arc second.

(*maximum speed with the G-8. Expect approximately 6 degrees per second with G-11)

The Gemini system will also accept inputs from optional shaft encoders (the same as used in Losmandy digital setting circles), which allow the telescope to be positioned by hand, yet still retain pointing information. Hand movement of the telescope will drop positional accuracy to that of the shaft encoders, but this can be easily refined using a quick synchronization or alignment position from a nearby object, which will return the system to full motor encoder accuracy.

Gemini can be used as a stand alone system in the field. It can be powered by any 1500+mA, 12-18 Volt DC source. No personal computer is required.

A user brightness adjustable LED display allows navigation through all internal databases for field use without a PC.

The following databases comprising about 41,000 objects are built into the Gemini system, more than enough to keep even the most avid observer busy for some time!

Messier catalogue (110 objects)

NGC revised (7840 objects)

IC revised (5386 objects)

Sharpless 2 (313 objects)

Bright Stars (167 objects)

SAO Stars (17635 objects)

A Deluxe Hand Controller (pictured above, right) is standard for all Gemini systems. The hand paddle features membrane switches which provide excellent tactile feedback, while providing a moisture proof seal for the internal electronics. The display works in parallel to the main electronics, allowing users to access all of the main panel functions via the palm of their hand.

Gemini uses a Meade LX200 command sub-set, with most LX200 commands being implemented.  The user can update the internal real time clock via the PC link as well as user location information. Coupled with The Sky by software Bisque and CCD camera, users can confidently determine the positions of minor planets and comets, and place them on a CCD detector time and time again.

How accurate is Gemini? 

Pictured (below left) is a T-Point summary of a 60 star mapping run with a Losmandy mount fitted with Gemini.

Note the Sky RMS pointing of 26.27 arc seconds.

While some manufacturers claim incredible accuracies with their GoTo systems, few will actually state actual results as shown.

While single star alignment assumes that your Losmandy mount is accurately polar aligned, the Gemini system only requires rough polar alignment to deliver excellent pointing accuracy across the entire sky using multi-star alignment models.

The Gemini system has an impressive list of features

• Very High Precision pointing to less than 1 arc minute
• Object search mode with user definable search radius
• Sidereal, Solar Lunar and King tracking rates
• User brightness adjustable LED display
• Up to 256 alignment stars permitted either side of the meridian
• Menus are accessed by the standard Losmandy 4 button hand paddle 
• A deluxe hand paddle that repeats the Main panel display information
• RS232 serial port control by a PC using software such as The Sky, Guide 7.0 or Palm Planetarium
• T-Point (Software Bisque) Compatible
• Internal real time clock that displays, UTC, Local Mean Time an Sidereal Time
• Up to 10 degrees per second slewing (G-8)
• User definable Guiding, Centering Slewing and GOTO speeds 
• Permanent Periodic error Correction
• Allows manual telescope movement with optional shaft encoders
• Southern and Northern Hemisphere operation
• Retains position information after power off (for permanent observatory use)
• EPROM upgradeable software

The Gemini design incorporates surface mounted PC board technology for reliable performance in the field. The main control board also has autoguider and accessory ports to allow full remote control of the system, either via a local PC, via a LAN or via the internet. (Gemini has been successfully tested with Software Bisques IAS server software)

The Gemini system has built in "T-Point" like pointing software that can use from one to many stars to refine its pointing accuracy. With multi-star modelling pointing accuracy has been measured to within three arc minutes around the entire sky, and to less than one arc minute with short slews from an updated position located within a few degrees of a reference  object. Gemini is also fully T-Point (Software Bisque) compatible. Extended personal computer based T-Point modelling runs can give better than 1 arc minute positioning accuracy across the entire sky! Further, with Gemini's warm re-start option, previously stored PC T-point data can be reused without the need to conduct a short mapping run.