Gemini-2 and Gemini-1 Telescope Mount Controllers
Website and Tutorials by Thomas Hilton
only search
There is a new Question and Answer Wiki section where you can ask searchable questions.

Several Operational Warning.
WARNING: The Battery circuit in the Gemini-2 is much different than in the Gemini-1. The battery connects through a small .2v Zener diode directly into the ARM processor. The Data sheet LPC2388.pdf states Vi(VBAT), the separate input for the RTC and the SRAM, has to have 2.0V at minimum, typical 3.3V and 3.6V at max for operation. With the Zener diode in the line, that means that a battery voltage between 2.2V and not exceeding 3.8V would be acceptable. A note states that the RTC typically fails at 1.6V (1.8V at our battery). This means that connecting an external Battery pack in place of the internal 3.3V battery will probably damage the ARM processor, So don't DO IT. Also After replacing the battery, Power on the Gemini-2 and set the time and date. Failure to do so could cause the processor to draw too much power from the battery and might result in processor damage.  You can also save all your setting using the Web interface Firmware/SRAM page "Store SRAM" content to file before removing the battery, and then "Load SRAM" content from file (to restore all the setting back to what they were before changing the battery), after you replace the battery..  This will not set the date and time, you still must do this!. Here is a video of changing the CR2350 battery. Here is a video of changing the CR2450 battery in the Gemini-2 Mini.

Now when Losmandy receives the circuit boards, the battery has a peace of paper or other material between the positive contact and the battery to keep it from powering the ARM processor.  What Losmandy does first, is to power up the Gemini-2, set the time and date, then pull out the paper or material.  This way, the ARM processor does not have a chance to pull excessive current.  You can emulate that on the original Gemini-2 version by putting a small circle of plastic on top of the new battery before putting it in.  Then power up the Gemini-2, set the date and time and remove the plastic.   I don't have a suggestion for the Gemini-2 Mini, as I have only seen pictures of it.  I am open to suggestions.

If you are connecting more than one Gemini-2 to your local network please see this FAQ1

WARNING: The Gemini-1 has several Startup modes. If is your habit of leaving the Gemini-1 powered on and parked, when not in use, then you should always make sure that you use one of the two options below. This is because if you have a power failure, and then power is restored, and the mount is in Cold Start, Warm Start, or Warm Restart, then the RA motor will start running at the tracking rate set, and can possibility run your telescope into your roof, or a limit, without you knowing it until too late:
   1. Set your startup mode to  "ASK IF POSSIBLE."  or
   2. Put the telescope into terrestrial mode tracking after parking.  Just remember to switch it back to Sidereal mode when starting up again.  This is the safest option.

Now the Gemini-2 starting wiith the Firmware of August 22, 2013 has special Park modes.  If you use a park mode 0 then it is pretty much like the Gemini-1.  If you use a park mode 1 or Park mode 2 then it takes an external event such as a GOTO command in Park mode 1, and only an UN-Park command in Park mode 2 to move the mount.

If you are remote, you might want to consider an Ethernet controlled power switch. I can recommend the switches from such as this one: Web Power Switch 7

WARNING: Do not update the firmware on on the Gemini-2 using just battery power, unless you are very very sure your battery is fully charged, and will not drop below +12V during the update. If the battery drops below +12 volts, the update can be corrupted, making it where you have to remove the micro SDcards and program them manually using a micro SDcard reader writer.

WARNING: The new Level 5 Version 1 firmware has a new mode, Alt/AZ. It you have a Equatorial mount, and the Gemini-2 is controlling and connected to it, Do not Select the ALT/AZ mode. This could cause the motors to slew your Equatorial mount into surrounding hardware. This is because the limits for an ALT/AZ and the parking locations are not even close to what they are for an Equatorial mount.
Page last updated on Jun 15, 2015
Bottom page
This site is not for profit and sells nothing and asks for no money for any help it provides.  This site is here to help fellow Gemini-2 and Gemini-1 owners. This Web Site is not associated with Losmandy-Hollywood General Machining Inc. or any of their employees and never has been. There is no guarantee that all the information is correct, but strives to provide the best information possible. The use of any information is at your own risk.  The webmaster is an unpaid beta tester, and tries to work with other beta testers, and René the writer of the firmware.  If you would like to help keep this web site going send your gift to Your gift will be used to defray the cost of keeping this web site up, unless you specify otherwise.
Hit counter by Hit Counter by Digits
Your Privacy Policy
No Information is collected by this site.  Cookies are set in your browser, but only for visited
links to change color.
Your use of any information on this site is at your own risk.

Gemini-2 and Gemini is a registered trade names of Hollywood General Machining Inc.