Gemini-II – Ascom

For the first 8 months I’ve used my Losmandy G11 with Gemini-II I only used the Hand Controller to slew, center, create models, auto-guide, etc. In some ways, I am glad I did: it was pretty instructive.

Then the firmware for Gemini-II became more mature and so did the Gemini Ascom drivers. While I can’t say for sure I experienced auto-guiding problems because of the firmware, Pulse-Guiding through Ascom is supposed to be more reliable anyway.

Here is a small guide to setup Ascom for Gemini-II and configure Stellarium to interface directly with the mount.

Prerequisites: You will need to install the following software before you continue. I am not detailing the installation steps as they are pretty straight forward.

  • Use an Ethernet cable to connect your computer to the Gemini-II controller.
  • Download and install the Firmware Update Program or make sure you are running the newest Gemini-II firmware. Visit for more details on setting up a network connection with the mount, etc.
  • Download and install the Ascom 6 platform.
  • Download and install the Gemini-II Ascom driver (click on “Gemini 2” menu and under “USB and Ascom Drivers” click on “Ascom Gemini Telescope Installer”.
  • Download and install Stellarium.
  • Download and install Stellarium Scope.

First start Stellarium and get used to the interface if you are not already familiar with it. You will need to select your location, for more precise GoTo I recommend that you set your exact location using GPS coordinates and altitude. Do not close Stellarium.

Make sure the mount is in CWD (counter weight down) position and power it on.

Open your web browser and go to the Gemini web interface, by typing: http://gemini/ this will ask your username and password. if you haven’t changed those, username should be “admin” and password should be left blank. Go to the Site/Time page and make sure your location and time are set properly.

Gemini Ascom Telescope Control:

Launch Gemini Telescope Control.

The window’s version of your hand controller will be displayed.

It is not connected yet.

Click on setup and make sure “Ethernet” is selected as the way to connect to the controller. Most of the other settings are your mount settings and will be updated when you are connected. Save the settings.

Click on the “connect” button. The hand controller window now shows tracking information and the “connect” button has been replaced by “disconnect”.

Stellarium Setup:

Go back into Stellarium.

Click on Configuration, then click the Plug-in tab. In the list, select “Telescope Control” and click “add”.

Enter a name for the “Telescope”. Technically, for us, it’s more a mount than a telescope, enter anything that makes sense to you. I chose “Losmandy G11 Gemini2”. Then click on “configure”.

Make sure you select Ascom as the connection method. The port can be set to any number, just make sure you remember what you set it to as you will need it to configure Stellarium Scope later. I chose port 10000.

Save the settings. You should now see a window similar to this one:

Now, connect the telescope you’ve just added. You can now close the configuration windows.

Setting up Stellarium Scope:

Launch Stellarium Scope.

Under “Scope Driver” click on the browse button […] and select “ASCOM.GeminiTelescope”.

Click “Connect”.

Under TCP/IP Socket, select the same port as you previously selected in Stellarium, in this case 10000.

Click on “Enabled”.

Now, if everything was done correctly at the bottom of the Stellarium Scope window you should read: “Socket: connected to” and “Scope: connected”.

Do not close this window but you can minimize as you shouldn’t need it anymore.

Using the Ascom Gemini Telescope Control:

The window’s version of the Hand Controller allows you to move the telescope just as any mount hand controller would. You can select between three speeds: G for Guide, C for Center and S for Slew.

You can start and stop tracking and access the mount configuration by selecting “Setup”.

There isn’t much else to say other than it is very handy. If you like me want to use programs such as BYE, EQalign, they all require you to look at the image produce by your camera and center a star for example. Instead of using your physical hand controller, you can just click and directly observe the result on the next window.

Using Stellarium to control your mount:

While it isn’t nearly as accurate as a good multi-star model, Stellarium GoTo’s can be very convenient. Especially if you plan on doing a few iterations of a drift alignment in preparation of a imaging night, you probably won’t want to spend too much time building a model to point at a few bright star for your drift alignment.

Once everything has been set up (if Stellarium Scope is connected to both Stellarium and the Scope) stellarium will now display an orange circle (target mark) with the name of the “telescope” you chose when you set up the Telescope Control plug-in for Stellarium.

If your mount is in CWD position and if you haven’t played with the hand controller yet, this target mark should be aiming at the NCP (North Celesial Pole) – if you are in the northern hemisphere at least.

In the example below, I am about to start a drift alignment routine using EQalign. I am using a western star, Procyon. To slew to a star, you need to first select it. Make sure you have selected the corrected star by looking in top left corner of Stellarium to get some information about the selected object (Name, Magnitude, etc). When selected, press CTRL + 1. You sometimes have to do this twice. A “Stellarium Telescope Control” window should pop up from which you need select one of two actions. In this case, click on “Slew Telescope”. The image below shows this example.

If your coordinates and time were set properly in Stellarium (and the Gemini 2 controller) it should be a farily accurate GoTo (assuming CWD position was accurate and a decent polar alignment was done).

You will most likely need to center this star on your camera or eyepiece. With an eyepiece, it’s probably easier to use the physical hand controller while looking through the eyepiece. With a camera, just use the window’s version of the hand controller to center it properly.

Once centered go back to Stellarium. The star should still be selected, so just press CTRL + 1 to and click on “Sync Telescope” to tell Stellarium precisely where the scope is aiming at. And your next GoTo’s should be slightly more accurate.

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10 Responses to Gemini-II – Ascom

  1. rob says:

    thanks for this article. if i ever get my G11/G2 this should come in handy.

    if after a slew and a sync you click “always do a SLEW”, will StellariumScope just unconditionally move the telescope when you press control-1 without popping up a window?

    • CooledPix says:

      Yes it would. I typically have to re-sync several times until I get my drift alignment right, so I pretty much never use the “always do a symc/slew” feature. If your time/location are set properly, and after a good polar alignment you should consider build a quick 3+ star model with the G2. Modeling is really more accurate than using Stellarium.

  2. rob says:

    i have heard that the G2 expects to have 2 models, one for west of the meridian and one for east. in my usual observing location i am “boxed in” and have maybe 3.5h of RA visible to me. i’m worried that i’ll never get a proper G2 model.

    right now i have a mount with analog setting circles and i have to do all my pointing the old fashioned way, so even a rough goto would be a huge improvement.

    • CooledPix says:

      You don’t need 2 models to have good modeling – most of the time, I only do a model on 1 side (east) as I typically stay on the same target the whole night.. In your case, just use whatever stars you have available. Starting from CWD it’s usually the first bright star you go to that is the most difficult to center. But if you get good CWD during day light even this shouldn’t be a problem especially if you’ve got a good finder scope well aligned with your main scope.

  3. patrice says:

    Hello Stephen,

    i installed all components and did all your parameters but when i looked in stellarium scope, i don’t have the same window, i have a black end red window like Ascom.
    Stellarium scope tells me that socket is connected with localhost on port 10000.
    When i go to stellarium my mount is connected.

    Am i right? excuse for my bad english (i m french)


    • CooledPix says:

      Hi Patrice,
      Stellarium Scope needs to be connected to both Stellarium socket and the Gemini controller. Make sure Gemini is connected, on my version of Stellarium scope there is a box to check to connect to the Gemini. Settings the main program (Stellarium) is tricky because it tends to reset setttings every time you go in the settings even if it’s just to verify something without changing anything. So make sure the telescope you’ve added in Stellarium is connected and on the same socket as Stellarium Scope.

  4. patrice says:

    Stephen thank you for the reply.
    but i don’t arrive to connect the mount with stellarium. there is no problem to control the mount with ascom gemini.

  5. patrice says:

    Stephen i try to control the mount with “cartes du ciel” software and i have no problem.
    but i don’ know if it’s better than stellarium and also i don’t know how to generate model because i always use the hand controler. how do you do a model with stellarium?

    • CooledPix says:

      the model with Stellarium is, AFAIK, only a one star model which is done after a synchronize. Resynchronizing on a new star wipes the model basically. You have to make sure Stellarium is set to the same time and location as the Gemini, this is easy to do.

      I am not sure why you can’t get Stellarium Scope to work with the Gemini, like I said the settings are tricky to get right but once done it works very well. Next time you have your mount out, take a screen shot of your Stellarium Scope screen and I’ll take a look.

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