Gemini-2 and Gemini-1 Telescope Mount Controllers
Website and Tutorials by Thomas Hilton
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Definitions
Adaptive_King_Tracking_Speed Alignment ARM
Ask if possible All_Speed_Mode Balance Menu
Battery Replacement Civil_Time_or_Local_Time Closed_Loop_Tracking_Speed
Cold_Start Comet/User tracking Speed Crossing_the_Pole
CWD Home_Position Limits
Lunar_and_Solar_Tracking_Speed
Meridian_Flip
Model
Model_Parameters Object Search Park and Un-Park
Parking Modes 1, 2,or 3 Photo_mode Polar_Alignment
Polar_Align_Assist Polar_Axis_Correction Pulse_Guiding
Quick Start RA-DEC_Error and Tracking Heavy Duty Tracking ERROR Reset_Model
SD Card SRAM Sidereal_Speed
Sidereal_Time Solar System Catalog Synchronize
Target unreachable error Terrestrial_Speed Time_Zone_Offset
Undo_Last_Alignment Visual_Mode Warm_Start
Warm_ReStart Western_Go_To_Limit Programming_Serial_and_UPD_commands
TVC Memory types in G-2


Definition of terms:
  1. Adaptive King Tracking Speed: In the absence of the Earth’s atmosphere, sidereal rate tracking would be all that is needed to accurately track objects with fixed RA and Dec. coordinates (any object outside the solar system). However, because the Earth’s atmosphere refracts (bends) light, it complicates the situation. The light from an object close to the horizon must pass through more atmosphere than an object higher in the sky. It is therefore subject to more refraction, causing the object to appear to be slightly higher in the sky than it actually is. This is called refraction. As the object climbs higher in the sky, it is subject to less and less refraction, and catches up with its refracted image. This means that objects appear to move at a rate slightly slower than sidereal rate when they are close to the horizon. Several methods have been devised to compensate for this effect called "differential refraction.”
    The King method (published 1931 by Edward Skinner King) helps to avoid star trailing in photographs caused by differential refraction. Differential refraction may especially affect wide field photographs with long exposures.
    King proposed two measures:
    • Offsetting the polar axis slightly towards the zenith, and
    • Adjusting the tracking rate.
    The values necessary to accomplish this depend on the geographical coordinates of the observing site and the declination of the object being photographed. Gemini's Adaptive King rate tracking varies the tracking speed to match the required value for the selected object’s declination. The user must offset the elevation of the polar axis himself.

  2. Alignment:  Used to build a model. If no model is built, the first use of Alignment will do an Initial alignment. Additional use of the Alignment instruction will add stars to the model.  Note: that a model has to be built on both sides of the meridian.  To switch sides a meridian flip must be done.  When switching sides, (a meridian flip) the first Alignment will start building a model on the other side, if no model has been built on that side. Models can be built on either side of the meridian.  The gemini-2 will automatically switch between them according to which side of the meridian it is on. (Pointing to the west from the east side in not considered switching sides, and the reverse is also true. If a meridian flip has not been accomplished, you have not switched sides.) This allows you to include some western stars in your eastern model, and some eastern stars in your western model.  How doing this effects the model has not been tested yet.  When the results of doing this is known, I will change this paragraph.  If you are using the built in model builder, which has an East and West button, be advised that these two buttons only select stars on the East or West.  They do not select which model is being used.  To switch to the other model the mount must go through the pole.  An easy way to do this is to select a star that has a HA greater than +/-4.6  This almost always assures that the mount will flip sides.

  3. Ask if Possible: This selection will allow the telescope display the "Quick Start, Cold Start, Warm Start, or Warm Restart menu", if something has not been detected where a Cold Start is mandatory.  If the SRam has been corrupted, or the log file corrupted, then the Gemini-2 is more than likely going to force a cold start bypassing the above menu selection. Also a low battery in the main unit could cause the SRAM to lose it contents, and force a cold start.

  4. All Speed Mode: This mode is for centering, slewing, and guiding.
    You get to this mode by Menu-->HC-->Mode  and select All-Speed button.
    Again only the buttons on the back of the hand controller can change speed by pressing the opposite button. In this mode, all speeds are available, from Guiding Speed to Slewing Speed, by using the opposite-button trick. You can use this mode, for example, while drift aligning, when you need very fine centering of a star at the crosshairs and a fast move from the meridian to the eastern or western horizon. However, for normal observing, you'll probably select either the Visual or Photo Mode.  Guiding only works in "All Speed mode" or "Photo_mode"

  5. Balance Menu:  This menu is a HC menu see Menu-->Mount-->Balance on the hand controller. It indicates in PWM (Pulse Width Modulation) and offset, how much power is being supplied to the motor and, how far the motor is from the desired position, respectfully.

  6. Civil Time or Local Time - The time that you normally put on your clocks/watches.  If you are observing daylight saving time, that time would include the daylight saving time.  When observing daylight saving time, normally the time zone offset will be changed by +1.

  7. Closed Loop Tracking Speed: The preceding discussion of tracking rates assumes that the mount is accurately polar aligned, allowing tracking to be accomplished using only the RA motor. However, for visual observing sessions, there is no need for extremely accurate polar alignment. By selecting Closed Loop tracking, Gemini can accurately track an object even if polar alignment is off several degrees in any direction. Gemini does this by comparing the coordinates of the object being tracked with the actual coordinates of the telescope. If the  coordinates do not match, Gemini makes slow corrections in both RA and Dec. axes to point the telescope back at the object. This process of compare and correct is done about 22 times per second. Although Closed Loop tracking will keep an object centered for a long time, it is not a substitute for a good polar alignment – especially if you intend to photograph extended objects. A misaligned polar axis will lead to field rotation, an effect where objects in the field of view will rotate around the center. However, after having done a good polar alignment, Closed Loop tracking can be used to photograph slow moving objects, such as minor planets or comets. This can work even if the object moves at a varying speed, by repeatedly sending actual coordinates to the Gemini using a computer. Because Gemini uses modeling parameters to calculate coordinates, Closed Loop tracking is only available after a pointing model has been established.

  8. Cold Start: This assumes that no model has been build, or the mount has been physically moved, If the mount is moved In Latitude or Longitude, or even a change of it's position even slightly to the pole, or in vertical or horizontal position at all (anything that will change Polar alignment), you have to do a cold start. You start at CWD position with a cold start. It also wipes out your current models, on both sides of the meridian. This is the mode you use if you are mounted on a tripod.  If the tripod gets moved at all or bumped you will have to redo the cold start and your model. The processor uses the CWD position as an approximate starting point. When you do a synchronize or alignment on a bright star, the processor now has a known good point to start it's calculations from, and also resets the limits (using the numbers that has already been set) to there correct position.  If this is the first time you have done a cold start, then after the Synchronize/alignment on a bright star, go set your limits.  This is important, especially if you have a large scope mounted on your mount.

    Also see Warm Start and Warm Restart.

  9. Comet/User Tracking Speed: This rate is very complex and a separate web page will be generated for it.

  10. Crossing the Pole: this is defined as when the Dec continue to climb until it reaches 90 degrees, then when it starts back down on the other side you have crossed the pole.  Normally this is accomplished along with a meridian flip, but it does not have to be.

  11. CWD, Counter weights and shaft in a vertical Down position with Dec pointed to True North, or True South in the Southern Hemisphere.

  12. Home Position, Home position is a user defined position.  It can be used to park the telescope at any position.  It is normally used in Observatories that have roll-of-roofs to park the mount in an horizontal position so that a roof can be closed over the telescope.   You define it by moving the telescope to the desired position and then use Menu-->Park-->Set home position.  When coming out of this position you must use a Warm Restart.

  13. Lunar and Solar Tracking Speed: Neither the lunar nor solar tracking rates is constant. Since the orbits of Earth and Moon are slightly elliptical, the apparent speed of Moon and Sun will change. When you select the lunar or solar tracking rates, the tracking speed will be calculated based on the actual position and the position one hour later. Because the Moon orbits the Earth, its RA and Dec. change during the course of the night. The lunar tracking rate compensates for the RA component of that change; there is no compensation for the changes in Dec. While sidereal rate can certainly be used for visual lunar observing, the lunar rate will do a better job keeping the Moon centered in the telescope’s field of view. Since the Moon is relatively near the Earth, even the location on Earth where you are observing must be taken into account. The lunar tracking rate therefore takes the parallax into account by calculating top-centric instead of geocentric positions. Gemini computes the tracking rates by calculating the current position of the Sun or Moon and the position one hour later. While the tracking rate for the (distant) Sun will not change much during an observing session, the tracking rate for the Moon might vary significantly as its parallax changes moving from the horizon to higher elevations and vice-versa. You can reselect the lunar tracking rate periodically throughout the observing session to allow Gemini to recalculate the correct rate as needed. Because the Earth is orbiting the Sun, the Sun’s RA and Dec. do change during the course of the day, but much more slowly than the Moon's. The solar tracking rate again compensates for the RA component of that change, but not for the Dec. Since the difference between solar and sidereal rate is only about 4 minutes a day, you will see little difference between the two over a short period of time.

  14. Meridian Flip: The process of causing the mount to switch sides of the mount.  In the Gemini 2 you can do this when selecting a target by checking the flip box during a Go To command.  If the mount can flip to get to the target it will flip.  If it cannot see the target with a flip, then it will not flip even if the flip box is selected. See the limits page for drawing what is meant by East and West sides of the mount. Note the new Align menu selection on the hand controller does not offer this box for flip.  Only using the Go To button (located on the right side of the Menu button) will you get a the flip option box.  It will be at the bottom of the page of the object you selected. If you do a Go To --> Coordinate Input --> check the flip box, and then Go To at the bottom of the page, the Gemini-2 will do a meridian Flip to the current coordinates, but only if it can safely do so, and can reach the current coordinates from the other side of the mount. NOTE: The mount will never do a meridian Flip while tracking at any of the defined tracking rates.  It only does meridian flips during slews or GoTo's.  There are some programs that can control the mount and make it seem to do a meridian flip during tracking such as ACP and others.
    If you are using the Model builder to build a model and want to do a flip to the other model, you have to pick a star that is between (+/- 4.6 and 6 HA) using the opposite side (East/West buttons) IE.  If you are on the east side, hit the West button till a star comes up that has a HA larger than 4.6, and this will almost always cause a meridian flip.  This also holds true for the west side and want to goto the east side with a meridian flip.  Just hitting the other side button and picking a star, will not insure a flip to the other model.  It is this way so that you can add stars that is close to the meridian's other side to the existing model.  This helps in transitioning from east to west and back.  Also to ensure good meridian flips, while building a model use an alignment star that is close to zenith that can be added to the model on both sides of the meridian.  This will help with better GOTO's and better meridian flips. This site shows pictures of G11 and what goes on during a meridian flip.

  15. Model: This is the mathematical sum of terms that is built as one builds a model.  It is used to insure precise GOTO's.    Without a model, the mount really does not know the precise mechanical to physical star locations.  It takes into many mechanical attributes of the mount, such as polar misalignment, non-perpendicularities, and then flexure calculated as more stars is added to the model.  Since the Gemini-2 controller can control so many different types of mounts, with many different types of telescopes attached, there is no practical way to have a pre-defined model.  Also a pre-defined model would not be possible without perfect polar alignment.  Building models normally use the Bright Star catalog group of stars.  These provide the most accuracy.  You can however use any object in the sky except the moon and sun to build reliable models, as long as you can center on them.  There are two difference methods of providing a model in the Gemini-2.  One is more like what was done in the Gemini-1, while the other is a graphics hand controller guide you through building a model.  Please see G2_Verse_G1-Modeling. There are actually two models built in the Gemini-2.  One for the East side, and one for the West side. It is recommended that you put 8-10 stars into each model, with at least 1 star from the other side of the Meridian in each model.  Try to make sure the first two stars of each model are separated by at least 4 hours or more away from each other in RA, and then add more objects in between them. So far the Hand Controller checks only for HA and elevation, not for distances between the objects, but the hour angles are displayed for each object, so you can select it manually. These models are stored in the battery backed up SDam inside the main Processor.  You do have the option to store them into the micro-SDcard in the main unit, and also retreave them from this memory. They are never worked on from the micro-SDcard, only the battery backed up SDram in the processor.  Please note that the stars that are used to build a model is not retained.  Only the last star used in mormally known, so it can be removed from the model if necessary. 

  16. Model Parameters:  These are calculations in Arc-Seconds of the different pointing and alignment errors from doing a star alignment.
    • Alignment count - tells you how many points are in each model. Note there is an East and West model built separately.  However they can only be saved or restored together.  You cannot separate them.  See Web interface Page Modeling
    • Polar Axis Misalignment - can be calculated with 3 to 5 stars.  The amount that your telescope is missaligned from the polar axis.  This is also called Polar Axis
    • Orthogonally Error - This is calculated with the 6 through 9 stars. Orthogonally error is were the telescopes is not perfectly aligned Perpendicular to the RA Axis. This can be caused by the Telescope DEC axis Saddle plate not being Perpendicular to the RA Axis, or the telescope not setting in the DEC saddle plate Parallel to the saddle plate.  Other mechanical items can cause this but this is the most common.  This is also called Non-Perpendicularity on the hand controller model error pages. There are two values given. The first non-perpendicularity measure is at the pole, and the second at the celestial equator.
    • Flexure - this is calculated with 10+ stars.  This is how much the counter weight shaft is flexing.  It takes an alignment of 10+ stars on both sides of the meridian to calculate this.
    • Model Parameters:  These are calculations in Arc-Seconds of the different pointing and alignment errors from doing a star alignment.
    • Refraction is also adjusted for if a model is built. The setting in ASCOM driver allows you to turn this off for coordinates that are sent from your PC, since some software already applies this correction to the transmitted coordinates.

  17. Object Search: Object Search This menu allows you to search around where the mount is pointing. The field of view is in arc seconds, and the search cycles is how many times the mount will make a circle at the arc seconds of deviation from center. Hand controller commands are "Menu-->Search." Also see tutorial page.

  18. Park and Un-Park: Park is the act of moving the mount to a fixed defined position, and stopping all tracking movement.  Un-Park is releasing the mount from a fixed park position, but does not necessarily star up tracking again.

  19. Parking Modes - Parking modes defines how the mount and what rules the mount follows to perform an Un-Park. There are 3 different modes. The rules are in firmware after July 27, 2013
    • Every Move or Mode 0 - Every command that moves the mount wakes the mount up (current state). This includes pressing the directional buttons, changing the tracking rate, using any of the Un-Park button. If a computer is tied to the controller, then any command from it can also wake up the mount and it start tracking in RA.  I highly recommend using parking mode 2.  It is less convenient, but a much safer parking mode.  This is the default mode, and is the only mode in firmware before July 27, 2013
    • Goto Command or Mode 1 -  HC directional buttons, classical HC and AG inputs are ignored, but "GoTo" commands and un-park commands wake it up.
    • Explicit Wakeup or Mode 2 - Only a Un-Park command :hW# will wake the mount up.  This mode is there to provide compatibility with the ASCOM standard rules.  The Un-Park buttons in the hand controller, Web interface, and the Un-Park command in the ASCOM driver send this string to the mount.  Also checking the Tracking box in the ASCOM Driver will send that command.*   The ASCOM driver now has a check box under Configuring Park, that will select this mode of Operation.  Please note that parking or un-parking does not change from one mode to the other.  Only the Un-Park command in the ASCOM driver and HC will start tracking again. *Except as noted above.
    • The parking modes can now be changed in the Web interface on the Functions tab.
      See example functions tab.
  1. Photo mode: This speed is used for Centering and guiding.
    You get to this mode by Menu-->HC-->Mode
    Guiding Speed is the principal speed, so pressing a Hand Controller directional button moves the telescope at the selected Guiding Speed; Slewing Speed is not available. The following changes in speed are only available on the buttons on the back of the Gemini hand controller, or a Standard Hand controller if plugged in.
    Acceleration to Centering Speed is available in four stages (to allow easy centering of an object in the field of view or on a CCD chip) by pressing the opposite button while Gemini is guiding:
    Pressing the opposite button once changes to 1/8 of Centering Speed to allow fine centering of the target. Then, after about 2 seconds, the speed will increase to ¼ Centering Speed, after another 2 seconds to ½ Centering Speed, and finally to full Centering Speed. Pressing the opposite button twice changes to full Centering Speed immediately.
    If you want to guide a photograph manually, you may do so by plugging a Standard  Hand Controller into Gemini’s autoguider port. This way you are sure that you cannot accidentally move the scope at centering speed while guiding.  A Standard Hand Controller is available from Losmandy under part number HC for $70.00 (price subject to Losmandy's current pricing schedule.)

  2. Polar Alignment: when the mount physical position (not the telescope) is aligned in AZ and Alt to true north, or true south. After any type of polar alignment, where the mount horizontal axis or vertical axis is moved, you have to start at CWD again and build a new model.  Moving the mount in horizontal axis or vertical axis invalidates the mathematics used to build a model.  In this regard, any model in the mount has to be disregarded, and rebuilt from the start.  Also don't expect to be able to see Polaris in your telescope at CWD after doing a polar alignment. This is mainly do to Polaris not being at true north, but a bout 3/4 degree off of true north.

  3. Polar Align Assist:  This is a routine that will help get the telescope into 1 degree alignment of the pole. It is a pretty simple routine.  You have to do it after a cold start, and with no model built.  The routine will ask you to pick two stars.  You should pick the first about +/-6 hours from the meridian, and the second on as close to the meridian as possible.  For the complete procedure see this page.

  4. Polar Axis Correction: This routine will be available after a model is built.  Asking for it will move the mount to a star.  You then use your horizontal and vertical mount controls (not the buttons on the Gemini controller) to center the star.  After this is done, you will have to build a new model, as the PAC routine wipes out the current model.

  5. Pulse Guiding: - This is when the guiding commands are sent as serial commands to the Gemini-1 or Gemini-2, and do not use the Guider ST4 input jack.  These commands can be sent into the Serial input, USB input or by using the ASCOM Gemini.net driver the Ethernet input of the Gemini-2. The Gemini-1 only has a Serial input.  Note that the ASCOM Gemini.net driver can use any of the serial, USB or Ethernet inputs to provide pulse guiding, but is not required if the software doing the guiding has native Gemini driver of it's own.  But the ASCOM Gemini.net using Ethernet is the suggested mode, as it provides the fastest communications speeds, and requires less PC overhead. All the modes below are a form of pulse guiding.
    • Non-Precision Guiding - non-precision pulse guiding uses the PC to tell Gemini when to start guiding movement and when to end it.  This mode is used with the Gemini-1.
    • Precision Pulse Guiding - telling Gemini on how long the pulse should be. The PC then gets out of the way, letting Gemini control the length of the pulse. Gemini-2 can use this mode, where Gemini-1 had some problems doing this. This setting should be turned off for Gemini-1.
    • Asynchronous Pulse guide - Asynchronous Pulse guide means being able to send the pulses asynchronously and not having to wait for the Gemini to complete the correction. This means that both, RA and DEC can be guided simultaneously. Both, Gemini-1 and Gemini-2 can use this mode and this should be left turned on for best guiding results.
    • Synchronous Pulse guide - When a pulse is sent, the driver/PC needs to wait until that pulse correction is completed by Gemini before continuing.  This mode may be used with some older software that does not allow both axis to be guided simultaneously.

  1. Quick Start: This menu offers the select where it leads you through entering all of of your location data, such as time zone, mount type, and location

  2. RA-DEC_Tracking_ERROR and Heavy Duty Tracking ERROR: These are messages telling you that the tracking error in RA or DEC has exceeded the set threshold as seen at the bottom of the Servo Page on the Web interface. They are set to 30 as a default, but you can change them to anything you want.  Do not change the RA or DEC Slewing Power Percentage.  You can change the RA/DEC Tracking Lag or the RA/DEC Tracking Power Percentage.  The higher values will lessen the messages seen.

  3. Reset Model: clears the model, for the side the telescope is on. To clear the model for both sides of the telescope, you must do a meridian flip to get to the other side, then Reset the model on that side also.

  4. Sidereal Speed: Sidereal rate is simply the rate that compensates for the Earth’s motion relative to the celestial sphere. It keeps the mount pointed at a constant RA and Dec. coordinate in the sky and will probably be the rate that you use the vast majority of the time. With sidereal tracking selected, the telescope makes one revolution per sidereal day (86164.0905 seconds). Note: The sidereal rate assumes that your mount is accurately polar aligned.

  5. Sidereal Time Sidereal time is measured according to the positions of the stars in the sky. A sidereal day is the time it takes for a particular star to travel around and reach same position in the sky. A sidereal day is slightly shorter than a solar day (24 hours), lasting 23 hours, 56 minutes, and 4.1 seconds. A sidereal day is divided into 24 sidereal hours, which are each divided into 60 sidereal minutes, and so on.   You can use this site to calculate your local Sidereal time from your Longitude: http://tycho.usno.navy.mil/sidereal.html or for a much more detailed explanation see:  http://aa.usno.navy.mil/faq/docs/GAST.php

  6. Solar System Catalogs:  These are not really catalogs at all but are calculated by the Gemini-2 internally.  Any that are highlighted, brighter (looks like they are already pressed), are not visible objects.

  1. Synchronize: Synchronizes the telescopes current pointing position to the built model stored in the Gemini-2. This is normally used after a Warm Start.  It may also be used to synch the model for more accuracy if looking for dim objects, by synching on a close bright object.  Synchronize does not modify the models math terms at all.   Now if a model has not been built, the it can be used after a Cold Start to give the Gemini-2 a really precision position for it calculations of where it is pointing at.  Now for the mathically inclined here it is in math terms:
    The model is a mathematical equation. Sync changes just the two linear components of the equation (HA index and DEC index), while additional align modifies coefficients of the non-linear terms (polar axis offsets, cone error, etc.)  Because Sync keeps all the non-linear terms intact while adjusting the linear offsets, you can keep Sync'ing as many times as you want without destroying the more complicated (non-linear) model.


  2. Target Unreachable Error: The target Unreachable error is most likely caused from one of the setting being set wrong.  The most common is the Time_Zone_Offset being set wrong.   The second thing is the limits being set wrong.  Also make sure that the site information is correct. If all this is correct, then a bad Polar Alignment might be the problem or the limits are set narrow like on MI-250 mounts. 
    Here is some suggestions on preventing the Target Unreachable Error Message:
    • Users with mounts that have narrow limits like the MI-250 or having special setups do need a good polar alignment for pointing near the Zenith. They should use PAC or drift align. A bad polar alignments always leads to an unreachable cone around the pole, most users understand this or don't mind it. The Zenith is a well-observed area, so to point there the RA axis has to be at a+/- 6 hours.
    • Pointing to the Zenith from the East side is better than pointing to it from the West side, because the GOTO limit is not effective there. But if the "Target unreachable" message appears, the firmware has already calculated pointing for both sides w/o success. Only a better polar alignment will help here (with rather narrow safety limits) to avoid this.
    • Is there a better Western GOTO limit than 2.5 degrees, that would give a little more latitude in preventing these unreachable error messages. Answer: Earth rotates once every 24 hours, that makes 15 degrees/hour, 2.5 degrees give 10 minutes. If less time is sufficient, f.i. for taking a short picture, the Western GOTO limit can be decreased. One degree gives 4 minutes of tracking to the the limit, but it may beep.
  1. Telescope Speeds: Gemini allows tracking in 6 speeds: Sidereal, Lunar, Solar, Adaptive King Rate, Closed Loop, Comet/User Defined, and Terrestrial (tracking turned off). In addition, the Hand Controller permits the user to move the telescope in both RA and Dec in 4 speeds that are established in the setup menu: Guiding, Centering, Move and Slewing. The user can also perform Go To movements of the telescope at a separate speed that is also established in the Web Mount setup menu. When a Go To operation occurs, the telescope moves at Go To Speed, and then slows down to Centering Speed as it approaches its target. Telescope parking is a separate command that disables tracking and moves the mount to a predetermined Home position – by default, counterweight down with the telescope pointing to Celestial North. Finally, all telescope movement stops and an alarm sounds when the mount slews to either its Eastern or Western safety limit. A warning also sounds when the mount approaches its Western limit while tracking.

  2. Terrestrial Speed/None: This rate turns tracking off completely and allows you to observe stationary objects such as points on land, or geosynchronous satellites. It is also useful for keeping the telescope from exceeding its safety limits when the Gemini must be left on for extended periods of time between observations.

  3. Time Zone Offset: - This tells the Gemini-2 which time zone you are in. When you use this along with your Local time or Civil Time, the Gemini-2 can calculate the correct Coordinated Universal time (UTC), also known as Zuzu time or Greenwich Mean Time.  This time zone offset can be in whole Positive or negative numbers. For the ones that live in half or quarter zones, you can also enter the hour:minute of your time offset, such as +09:30 for the Northern Territory of Australia.  See Time Zone Facts  and Time Zones.
    For the ones of you that live in the United Kingdom, when you are observing daylight saving time, you will need to use an timezone offset of +1, with your local time, for the Gemini to calculate UTC correctly.  

  4. Undo Last Alignment: Removes the last star added to the model.  Can only be used once.

  5. Visual Mode: This mode is for Centering and slewing.
    In visual mode, the Guiding Speed is not available. When you press a button, the telescope moves at Centering Speed.  The following only applies to the buttons on the rear of the hand controller. Momentarily pushing the opposite button lets the system accelerate to the manual slewing speed. If you are moving both axes, both will speed up. Ramping up and down in speed occurs independently for both axes. This mode is intended for visual observing and for looking up objects. The auto-guider port is not active in this mode.  Again, The Gemini-2 will not guide using the Guider inputs or theough The Ascom driver if the Gemini-2 is in "Visual Mode"

  6. Warm Start: This assumes that a model has been made, and the physical mount (Pier) has NOT been moved in any way, including Latitude or Longitude, vertical or horizontal position (the mount is permanently Pier mounted), but the RA or DEC could have been moved. Warm Start assumes that the mount is in the CWD starting position. 

    The processor uses the CWD position as an approximate starting point. When you do a synchronize on a bright star, the processor now has a known good point to center the model around, and also resets the limits (using the numbers that has already been set) to there correct position.

    Also see Cold Start and Warm Restart.

  7. Warm ReStart: This mode assumes that the mount has not been moved in Latitude, Longitude, vertical or Horizontal position (the mount is permanently Pier mounted) and also RA and Dec has not been moved. You do not have to start from CWD, but start from the current RA and Dec position. (If you parked at CWD, then CWD would be the current RA and Dec positions). However it can start from any position that is was powered down in, like horizontal in the case of roll off roofs. It also assumes a model has been built.

    The processor uses the last stopping position as an known starting point. The processor will center the model around that, and also reset the limits (using the numbers that has already been set) to there correct position.

    Also see Cold Start and Warm Start.

  8. Western Go To Limit: allows you to define a point past which Gemini will always Go To the object so that the telescope tube is on the east side of the mount. Gemini will allow the mount to track past this point, but will not Go To any object west of this point without a meridian flip, if needed, to put the telescope tube on the east side of the mount. The default value, displayed as 0 degrees, sets the Go To limit to the western safety limit minus 2.5 degrees, allowing for at least 10 minutes of tracking. This can be set on the Web interface under the Mount tab, or on the Hand Controller under Menu-->Mount-->Limits

  9. Programming Serial and UPD commands:  The use of the serial commands that tell the Gemini-2 what to do, and how to use the UPD command sequence to send these commands through the ASCOM Gemini.net driver are covered in these two documents.
    1. Serial Command Set
    2. UDP Protocol
  1. TVC: (Time Variable Compensation) This menu item helps compensate for the response delay caused by gear backlash when changing direction in Dec. The TVC can eliminate the hysteresis that causes this to Gemini Users Manual 67 happen. You can select a value between 0 and 255, which is the number of steps made at high speed whenever the Dec. direction is changed. You should choose a "TVC Value" that results in a short or no delay when changing the guiding direction in Dec. If you see a short jump, you have to decrease the value.

    So, the number is the number represents motor steps taken at high speed when reversing DEC direction. For a G11, one step is approximately 0.56 arc seconds, so value of 50 means rotate the motor by about 28 arc seconds to take up backlash. Maximum value of 255 provides for about 143 arc seconds of backlash.

  2. Memory and ARM: There are several types of memory used inside the Advanced RISC Machine, which is a family of reduced instruction set computing (RISC) architectures for computer processors normally refered to as ARM microprocessors. The main board uses one and the hand controller has a smaller version of one. SRAM, and SD RAM described below.
    • Internal Memory.
      • 512K of Flash memory.  This is the memory that holds the program that runs the Microprocessor, and also the boot loader. This memory holds it contents without battery backup.
      • 32K of battery backed up Static Ram "SRAM" for storing variables.
      • 16KB for the Ethernet interface. The Hand controller ARM does not have a Ethernet interface.
    •   External Memory:
      • A micro-SDcard, usually 2GB in size, but can be bigger.  This is used to store the English, German, French, and Spanish Web interface menus.  It also stores the star catalogs used in the main unit.  (The hand controller stores it's own catalogs).  You can store a copy of the Models, copy of PEC, Copy of the values stored in the battery backed up Ram.  It also contains the Mobile Hand controller if loaded, and a directory containing the Gemini configuration.   It can also store the videos that Scott has produced if you wish to upload them to it.


  3. The Hand controller ARM processor contains much the same memory types, but they are used differently.
Page last updated on Apr 19, 2017
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