The Losmandy Gemini system is a DC servo motor-based go-to computerized positioning system designed for the Losmandy HGM200, HGM Titan, G-11, and G-8 mounts and the Celestron G-9 and CI700 mounts. The servo motors used in the Gemini systems have two main advantages over the stepper motors normally used in the scopes. First, servo motors run with a continuous smooth rotation, rather than the discrete short steps taken by stepper motors. This results in less image “jitter" in extremely high magnification planetary observing and stars that are tighter and more point-like in critical astrophotography applications. Second, servo motors have very high torque, even at high slewing speeds. As a result, the Gemini system can deliver up to 10 degrees per second slewing with the G-8 mount, yet still retain motor positional information of about 1/10th of an arc second. The maximum slew rate with the heavier-payload HGM200, HGM Titan, G-11, and CI700 mounts will be approximately 6 degrees per second.
The Gemini system accepts inputs from optional shaft encoders (the same #DSCH used in Losmandy digital setting circles), This allows your telescope to be positioned by hand, while still retaining its pointing information. Hand positioning of the telescope will drop the system positional accuracy to the lower accuracy of the shaft encoders. However, 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 1500mA, 12-18 Volt DC source. No personal computer is required. A user-adjustable variable brightness red LED display allows navigation through all internal databases for field use without a PC. Menus are accessed through the standard Losmandy deluxe 7-button LED display hand control. The hand control features membrane switches that provide excellent tactile feedback and a moisture-proof seal for the internal electronics. The display on the hand control works in parallel with the main electronics, allowing users to access all of the main panel functions via the hand control.
The following databases, comprising about 41,000 stars and objects, are built into the Gemini system, more than enough to keep even the most avid observer busy for some time! You get the Messier catalog (110 objects), the revised NGC catalog (7840 objects), the revised IC catalog (5386 objects), the Sh2 Sharpless 2 catalog (313 objects), a catalog of 167 Bright Stars, and a 17,635 star catalog of SAO Stars. (The above database links will take you to ASCII text listings of each catalog.)
The Gemini system has an impressive list of features. You get very high precision pointing to less than 1 arc minute accuracy. You get an object search mode with a user definable search radius. You can select tracking at sidereal, solar, lunar, or King tracking rates (which compensates for atmospheric refraction for more accurate tracking near the horizon). Up to 256 alignment stars are permitted on either side of the meridian, not just the 20 or so total available at any one time with other computer systems.
There are user definable guiding, centering, slewing, and go-to speeds. Permanent Periodic Error Correction (PPEC) is included. Both Southern and Northern Hemisphere operation is built in. The Gemini retains its position information after power off (for permanent observatory use). The software is EPROM upgradeable. You can control the Gemini from an optional laptop PC or Palm Pilot through an RS-232 serial port using optional software such as The Sky, Guide 7.0, or Palm Planetarium.
The 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 a CCD camera, users can confidently determine the positions of minor planets and comets and place them on a CCD detector time and time again.
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 modeling, 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 modeling 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. Only Losmandy Gemini gives you T-Point-like accuracy in the field with no other software or accessories! The model updates around the last alignment object; hence for short slews the system can easily position objects on every commercially available CCD chip every time.
Gemini's non-volatile memory and real time clock data also allows the system to be powered off, and restarted at a later time with no loss of modeling data or positional information. The re-start position accuracy is only limited by the accuracy of the internal clock, which can be updated to within a fraction of a second via a PC. These features make the Gemini system ideal for astrometric and photometric surveys (e.g. comet and asteroid hunting, supernova patrols, variable star studies) and are well suited to permanent telescope installations.
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