|Gemini System Ovserview|
The Gemini System provided with our Losmandy Mounts includes an evolution of the mount operating functions described on the main Gemini system description page. The mount operating instruction set (or "operating ROM") is a socketed computer chip, housed in the Gemini Console illustrated at right.
Losmandy "Gemini" control system Console. This houses the control circuitry of the Gemini system, and the interface to external components, power supply, and motors.
The basic functions provided with the mount are referred to as "Level 1 ROM". These have evolved as bugs were worked out of the Gemini, and these changes are referred to as "Version" changes. So a chip that is "Level 1, Version 1" is not as desirable as "Level 1, Version 1.1". By the year 2002, Rene Goerlich had developed the Gemini to provide three levels of functions (1, 2, 3) each with increased functions and capabilities. To change from one Level to another, or to upgrade from one Version to a more refined Version simply requires one to acquire that chip, then install it into the Gemini Console.
An upgrade chip to Level 3 (sometime written "Level III") and Level 4 are available for a relatively modest fee. While it is possible to buy the chip and upgrade at some later time, Company Seven suggests that for most people is worth while to order this upgrade factory installed with a new Mount since it will become confusing to learn a new menu all over again if one transitions from Level 1 or 2, to Level 3 of 4 as an aftermarket upgrade at a later time.
The official Gemini developer's site gives Gemini users additional information to make best use of their telescope control system. Please contact the mount manufacturers or one of their dealers if you want to order the Gemini hardware for your mount. Check this site or contact Rene Goerlich if you already have the Gemini and want to upgrade the software to a higher level, if you want to propose new features to be added, or if you experience problems.The Gemini System comes with the German Equatorial Mounts GM-8, G11, Titan and HGM-200 produced by
The Gemini is a sophisticated computer controlled servo system with
lots of valuable features.
Based on 3 microprocessors (one per axis and a main CPU), it is self-contained and fully functional without the need for PC control in the field.
To allow for an ongoing development, Gemini software is build and supplied in several levels of functionality. The Gemini system is currently sold (with a mount or as a retrofit) with Level 3 software. Within each level, the software is maintained and changes are indicated by a version number. Levels 1 and 2 are no longer supported, an upgrade to Level 4 is recommended.Changelog of the software released so far:
|July 2001|| |
Level 3, V1.03
|Level 3, V1.11||
|Level 3, V1.12||
|Level 3, V1.13||
Owners of a Losmandy Gemini System are entitled to upgrade to the current software. This can be done by replacing Gemini's socketed eprom chip. The new software is available for free download.
You need an 512kx8 EPROM in the DIP32 package, up to 120ns access time, 150ns usually works, too. Examples are STS M27C4001, National NM27C040 or Fairchild FM27C040. Please use the eraseable kind with the little window allowing for erasing the content with special UV light, not the OTP (one time programmable).
The software is available as an image in Intel HEX record format or in binary form. Please be sure to select the the correct format programming device.
Often computer and electronics shops offer to burn images into EPROMs. Don't forget to cover the UV window after erasing and before burning the new image into the EPROM.
Instead of programming a chip yourself those who bought their systems from Company Seven can buy ready to use Gemini Eproms through us.
Level 3 Version 1.13 software is still available as
Company Seven makes the current Level 4 Version 1.02 available on line:You may want to use the "Save Link Target As" feature of your browser.
Here's an article "Replacing the GEMINI System EPROM Chip" explaining how to locate and replace the EPROM .
Gemini offers many features to the beginner as well as to the expert. To make best use of it I highly recommend to read the very comprehensive manual written by Dave Sandage, Michael Rudolph and me. The manual is available for download in Portable Data Format (.pdf):
Software developers wanting their programs to communicate with the Gemini: Here are the Serial Line Command Interface Descriptions (these links will open new browser windows) :
If you want to connect a cute little GPS receiver to set your mount's date, time and location automatically a startup, check for the GPS-6010 or GPS-6010-LX receivers (the link opens a new browser window)!
A star chart with Gemini's bright and alignment stars can be found at duchekconsult.com.
With Level 4 software, the hand controller functionality can be emulated over the serial line. This allows to use the DB-15 HC socket to be used as a second serial port.
Thunderbird Electronics Inc. provides a serial RS232 adapter for the HC port:
You don't like to work through the menus of the Gemini? You'd like to save the
settings into a file and download them if necessary? Save the well tested modelling
parameters for your permanently mounted telescope? Or script control your telescope?
Level 3 and 4 software together with the Gemini Control Center contributed by the developer's son Daniel puts you in full control at the keyboard of your PC.
Visit Dr. Görlich's web site to read a detailed overview of the capabilities of the Gemini Control Center while working with the Level 3 software. For download and installation, please follow the instructions on this page !
Mike Rudolph and Daniel Görlich have written a comprehensive manual for the GCC (1 MByte .pdf file).
Gemini hand controller emulation takes over:
PEMPro now fully supports Gemini Level 4 Firmware. This allows for
dramatic correction and refinement of PE for all Gemini equipped mounts:
PEMPro provides direct upload and download of PEC curves to Gemini
firmware and beta testers have reported an average of 80% reduction in
Periodic Error using the new L4 firmware and PEMPro 1.6.
For technical information regarding specific Gemini L4 support please
siriusimaging.com PEMPro technical support.
For more information about purchasing or upgrading to PEMPro Version 1.6, please visit: www.ccdware.com.
* Includes possible duplicate or never confirmed object descriptions from the original catalog.
You can prepare your observations by building user catalogues using your computer and
and downloading them into the Gemini using the Gemini Control Center. Well prepared
observing, together with the automatic logging of your actions, can be much more
It is not possible to upload Gemini's databases to your PC. If you want to compile your specific observing lists for the night using the objects from the Gemini's databases, here they are in the Gemini User Catalogue (.guc) file format. You can download them, copy and paste your targets using your favorite editor, building up your specific programs for the night.
If you want to share experiences with other Gemini users, there are two Yahoo groups online:
Level 1 software contains
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!
Level 2 and 3 software additionally contains
You can prepare your observations by building user catalogues using your computer and and downloading them into the Gemini using the Gemini Control program. Well prepared observing, together with the automatic logging of your actions, can be much more effective.
It is not possible to upload Gemini's databases to your PC. If you want to compile your specific observing lists for the night using the objects from the Gemini's databases, they are available in the Gemini User Catalogue (.guc) file format. You can download them, copy and paste your targets using your favorite editor, building up your specific programs for the night.
In Level 1 or 2, on startup, Gemini did not know where it was pointing. The consequence of this was that Gemini could not slew to the initial alignment star using Gemini's GoTo capability. This limitation has been removed in Level 3. Gemini can now slew to the first alignment star if the mount is polar-aligned and the OTA is in a defined home position during startup. This feature also requires that Gemini have the correct latitude, longitude and UTC data.
To use this feature, ensure that the mount is in the CWD position before applying power. After selecting "Cold Start", simply choose an object from the database and select "GoTo". For even more convenience, Gemini offers a "GoTo Bright Star" feature, listing the commonly known bright stars currently above the horizon. Just select one of them, or a database object, and Gemini will slew reasonably close to the selected object. Use the hand controller to center the object. Now all you need to do is select the "Align Telescope" menu item and select "Synchronize". You can then add additional alignment stars as before.
Gemini's Level 3 software allows the user to set Gemini's longitude, latitude, UTC date and UTC time from a GPS receiver connected to the serial port. Any GPS receiver can be used if it is capable of transmitting either NMEA 0183 protocol or Garmin Textout protocol.
Gemini attempts to query a GPS when it is powered on. You can also explicitly have it read the GPS data by using the "Setup->Geogr. Location-> Query GPS Rec" menu item at any time.
Parking the OTA
The telescope can now be parked at any "Home Position" by either the hand controller or serial control. The home position defaults to the CWD (Counterweight Down) position.
The feature is accessed on the hand controller using the Quick Menu feature. Simply hold down the Menu button until the display shows "Park Mount!" The mount will then slew to the Park position. You can set any Park position by moving the mount to the desired position using the hand controller and then selecting the "Setup->Mount Parameter->Set Home Posit." Menu item.
Comet/User Defined Tracking
Comets and Minor Planets follow their own trajectories through the Solar System. Gemini can be commanded to follow their movement in a variety of ways.
Available on the hand controller is a Comet/User Defined submenu of the tracking speed selection. Once selected (after centering the object), a training phase can be started. Unlike training PEC, you don't have to follow the motions exactly. Just keep the object in the eyepiece for a sufficient amount of time. Finally, center it and press the menu button to end the training phase. Gemini calculates the necessary tracking rates in RA as well as in DEC and the mount will follow the object in both axes.
The amount of time needed for training will vary with the object and the type of observation. For an object with a relatively slow and constant motion, a few minutes of training should be sufficient for visual observing. For photography, you may want to consider training for up to half of the intended exposure time. For an object that changes speed fairly quickly (such as a Near Earth Asteroid), shorter training sessions just before the observation will work best. In general however, for an object with relatively constant speed, the longer the training (up to 45 minutes) and the more exactly the object is centered at the beginning and end of training, the better the tracking will be.
Alternatively, if you know the ephemerides of the object, you can input the actual position and the position in 1 to 255 hours together with this timespan. Gemini will set the tracking rates accordingly.
Additionally, new serial line commands have been added to allow the user to set his or her own RA/DEC tracking rates. This "User Defined Tracking" (to be used instead of a training phase) is useful for tracking minor planets and comets by setting the necessary rates using a computer program. For more information on how computer software can use these commands, see the Serial Line Protocol description.
Closed Loop Tracking
Gemini can be instructed to stay at, or slowly move to, given RA and Dec. coordinates regardless of how accurately the mount is polar aligned. The difference between the desired coordinates and the actual coordinates is checked about 22 times a second. If there is a difference, Gemini moves one step in the requested direction. This lets the telescope gently follow the coordinate at about 0.5x guiding speed.
There are several applications for this advanced tracking feature:
1. Visual observing. There is no need to precisely polar align the telescope for visual observing. The internal pointing model is not only used for the GoTo operation, but with Closed Loop Tracking also for keeping the object centered.
2. Tracking comets or minor planets. This requires a connected computer sending updated coordinates whenever the object coordinates change. The coordinates are to be transferred with the :Sr and Sd commands. No :MS# slew command is to be issued. If the use of the :MS# command cannot be suppressed inside the computers software, Gemini's "Move Lock" command :ML# can be employed to let Gemini ignore further :MS# commands.
Gemini allows you to center an object with the hand controller during closed loop tracking without moving back to the calculated position. The difference between the calculated and actual position is stored and added to the new coordinates within the correction cycles.
Western Tracking Limit Warning
While tracking, an audible warning (a short beep about every 20 seconds) sounds some minutes before the western safety limit is reached. This gives the user an opportunity to close his camera shutter or take whatever other action is necessary.
Gemini now supports focusing units having 9 to 12 volt DC motors (e.g. JMI's NGF series). In order to focus using the Gemini, you must have an adapter board accessory connected to the feature port.
The Gemini focusing function uses the Meade LX-200 serial line focusing commands. You can also change focus using the hand controller by putting it into focus mode. This is done by selecting "Focusing" from the Quick Menu. This menu item is only available if the adapter board was connected. When in Focus Mode, the RA buttons move in and out, and the dec buttons toggle between fast and slow focusing modes.
To disengage from the Focus Mode, press the Menu button.
Adaptive King Rate Tracking
Gemini Level 2 includes the option of constant King Rate tracking for objects at lower elevation. Level 3 takes this a step further by varying the tracking speed depending on the distance of the object above the horizon.
You can enable the adaptive King rate using the "Setup->Mount Parameter->Tracking Speed->Adaptive King" menu item.
Variable Solar/Lunar Tracking Rates
Earth and Moon move in slightly elliptic orbits. According to Kepler's Law, the velocity changes with the distance from the gravitational center. Gemini calculates the actual tracking rate necessary to follow the object at the moment you select the tracking rate (considering the motion within the next hour). For the Moon, the parallax is taken into account, too.
Enhanced Search Mode Features
The Search Mode can now be accessed by remote control, a feature particularly useful in video astronomy. In addition, a new "Z" shaped search pattern, "Wobble Object," was added to assist in recognizing faint objects.
Up to 10 bookmarks can now be placed at any coordinate in the sky, and Gemini's GoTo feature can slew to it. To set the bookmark, select the "RA/Dec Coordnt.->Set Bookmark" menu item. To have Gemini slew to the bookmark, select the "RA/Dec Coordnt. ->GoTo Bookmark" menu item.
You can overwrite old bookmarks using the Set Bookmark feature or add a new one as long as the maximum of 10 (0..9) is not reached. Bookmarks are stored permanently and can only be erased by a Reset Defaults operation.
New Modeling Parameter
The internal telescope pointing model of Level 2 has been extended to include "Counterweight Flexure," a refinement that takes account of the play and flexure in the RA axis assembly. It is automatically calculated after you have done at least 5 Additional Aligns. Polar Axis Correction
This feature assists you in accurately polar aligning your mount. Because Gemini's modeling feature calculates the mount's deviation from correct polar alignment, it can be used to guide you as you adjust the mounts altitude and elevation to achieve polar alignment. Although you can use this feature after a single alignment, it will be much more accurate if you first build an accurate pointing model by doing several alignments.
After you have done several alignments on different objects, select an object from the Object Database that is near the celestial equator and the meridian. Goto the object and center it in the eyepiece using the HC buttons. Now, select "Align Telescope->Polar Axis Corr." from the menu. Gemini will move the mount to where the object should be if the mount were accurately polar aligned. You should adjust the polar alignment of the mount using the altitude and elevation knobs until the object is again centered in the eyepiece. Since the mount will approximate perfect polar alignment, all subsequent GoTo operations should result in target objects being near the center of the eyepiece. If not (for instance, because the mount's initial misalignment exceeded several degrees), you may repeat the correction process. Note that after using this function, the modeling parameters will be reset and you will need to rebuild the model by performing several alignments on different objects.
Feature Port Access
Gemini's Feature Port can now be used to control user-designed hardware.
New PEC Functions
Level 3 provides a greatly enhanced set of PEC (Periodic Error Correction) features. Gemini L3 provides the following new PEC functions:
PEC Delay Correction - Advances the playback of PEC corrections to compensate for latency between the error and the correction during PEC recording.
PEC Drift Correction - Removes any systematic drift component from the recorded PEC data caused by differential refraction or polar misalignment.
Smooth PEC Data - Smoothes recorded PEC data to eliminate spurious corrections caused by seeing, etc.
Average PEC Data - Allows you to make multiple PEC training runs and average the results.
Restore Saved Data - Restores PEC data that has been moved to a backup buffer by a previous PEC command or an additional training run.
A convenient and fast place to (1) change Gemini's Centering Speed, (2) toggle between Visual and Photographic Modes, (3) Park the OTA, and (4) Focus via an auxiliary adapter board. To access these functions, simply hold the menu button down until the options start appearing on the display. When you see the option you want to select, release the menu button.
Simplified Sync Operation using TheSky
From Level 3, V1.01 up every location marked within the planetarium program TheSky can be used to synchronize Gemini's coordinate system without having to slew to the location before. This simplifies Sync and Image Link operations.
The Level 3 Menu Tree: