Telescope Control

Posted by Fabien Chéreau on 2019-04-05 at 10:32

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  • Author
    • #440
      Fabien Chéreau

      This is the place to get support for questions about telescope control on Stellarium Mobile Plus.

      Before asking, have a look at the page.

    • #455
      Sebastien Chidiac


      How to control my Celestron C9.25 with Stellarium+ ?

      It asks for a Host & Port.
      I can’t find any support for this… :'(


    • #457
      Fabien Chéreau

      Salut Sébastien,

      sorry for not having any good support on the telescope control feature yet. This thread is actually the good place to discuss it.


      – current Stellarium+ version (1.0.9) can only connect to a Stellarium Telescope Server or compatible 3rd party apps such as StellariumScope.

      In practice this means that you need a PC (or a rasberryPI) connected to the serial port of your telescope, and running the telescope server.
      If you have windows, you can download a pre-build version: TelescopeServerLx200.exe.gz for LX200 compatible mounts (Meade) or TelescopeServerNexStar.exe.gz for NexStar and compatible mounts (Celestron, SkyWatcher etc..).

      Stellarium+ expects the IP of this PC, and the port number you specified when starting the telescope server application.

      We are fully aware that this is not the easiest way to interact with a Telescope, but the good news is that I am actually spending most of my time (and nights!) coding proper support for Serial over Bluetooth and Serial over TCP socket interface. With that, instead of a PC, you will simply need a small Bluetooth to Serial or Wifi to Serial interface connected to your telescope.

      It actually starts working pretty well on my development version (I used it last night!) but it needs a lot of testing because telescope vendors have so many different hardware/protocol/firmware versions.

      I am about to look for beta testers with telescopes for trying as many setups as possible, so if any one reading this is interested, please let me know.

      May I ask you what your mount model /hand controller is, and how you’d prefer to connect to it from your phone?



      • #516
        Fabien Chéreau

        FYI: since the initial posts on this forum, the Telescope Control code has been completely updated and now works fine with NexStar, SynScan and LX200 and compatible telescopes. They can be connected using Bluetooth, WIFI or other network connection.

        The app was tested against a growing number of controller devices including:
        – Meade Audiostar/Autostar using Bluetooth or TCP connection
        – Celestron Nexstar+ using Bluetooth
        – Sky Watcher SynScan v3 and v4 hand controller using Bluetooth or TCP connection
        – Sky Watcher AZGTi WIFI mount, through android SynScan App
        – OnStep controller using Bluetooth

        Don’t hesitate to report success (or failure) with your own setup!

      • #577
        Devon Croll

        Hi Fabien
        Just got telescope control working via PC last night. I have a Skywatcher Synscan Wifi Adapter (no hand controller).

        Reading your posts above, can you connect directly to the mount via the wifi dongle or connect to the dongle via the synscan pro app?
        I think you are saying above that you connect the synscan app to the mount first , then stellarium mobile + to the Synscan pro app? Does that mean 2 devices, I think that is where some other programs get around it?

        Awesome apps thanks

      • #582
        Fabien Chéreau

        Hi Devon,

        for SynScan WIFI mount or adapter, you need to use the SynScan app because a specific UDP protocol is used (which is not LX200 or NexStar). The SynScan app on android creates a small server on IP emulating an NexStar serial interface, on which Stellarium can connect.

        So on Android you need only one phone, as the Synscan app can run in the background. On iOS currently you need 2 devices, one running SynScan and the other running Stellarium.

        Hope this is clear enough!


    • #484
      Anthony Hiscox

      It would be nice if we could have some kind of interface for programming our own “drivers”. I have a Celestron Nexstar 80GTL and I bypassed the RS-232 level converter in the hand controller and soldered in a HC-06 bluetooth adapter. I’m currently working on an Android app to send commands to the controller, including passthrough commands that go directly to the mount. I’ve also considered removing the hand controller entirely and replacing it with an Arduino Pro Micro and HC-06 to give me a USB PC port and Bluetooth to Android.

      I’m looking for an app that can output the coordinates of a selected entity so I can move to it. This lets me handle things like Cord Wrap, and limits in movement so the scope doesn’t hit the mount, as well as hibernate and whatever else.

      I’ve looked into modifying Sky Map now that it’s open source, but it’s not nearly as full featured as Stellarium. Also, I don’t have Plus yet but probably will soon. If you need any help Beta testing with the 80GTL that fits with my current setup (which is mostly the same from Android’s point of view as a RS-232 serial to bluetooth adapter) I’d be happy to help.

      • This reply was modified 1 year, 10 months ago by Anthony Hiscox. Reason: Corrected model
      • #486
        Fabien Chéreau

        Hi Anthony,

        thanks for the message, first of all, when we are ready to release the next version with update telescope support, the nexstar protocol should work fine, so it should be easy to send regular commands to your (bluetooth-ified) hand controller.

        For replacing the hand controller completely, the best would maybe be that you re-implement a subset of the nexstar protocol in your arduino so that you remain somewhat compatible with the nexstar driver of stellarium mobile +? You could then intercept the goto commands, and modify the behaviour according to your whishes.

        My current driver assumes the mount is nexstar-compatible if it correctly implements the echo command, i.e. when receiving a ‘Kx’ command it should return ‘x#’ with x any byte value. From this point the codes sends many comands but the only required ones are the ‘e’ and ‘r’ commands, for getting position and slewing to a position.

        Would that be a solution?


    • #488
      Anthony Hiscox

      This would work for an Arduino based solution, as well as passing commands to a properly aligned telescope via hand controller. Ideally things like Date/Time/Location would be set via the phone rather than an onboard GPS, and since I intend on mounting the phone to the eyepiece for the camera, leveling and pointing north for alignment could be automated.
      Will your implementation be doing any sort of alignment?

      I’m still working through any resources I can find, not sure how it all works yet. For example it looks like Time and Date can only be set with 2.3+ version firmware on controller, I have 1.2+. I’m new to astronomy as well and not a great programmer, so this complicates matters. Not sure if it makes more sense to do alignment on Android and only use the controller/Arduino for passing data directly to mount with Passthrough (0x50), similar to how auxremote (github) does it, given my 1.2+ firmware.

      In the meantime I considered a localhost HTTP server on Android emulating the Telescope Server Stellarium uses to implement some of these features. Is this protocol documented anywhere, or should I just look at the source?


      • #489
        Fabien Chéreau

        Be careful that without hand controller, the arduino would need to pilot the DC Motors directly, and there is no such thing as setting time/date/location for a DC Motor.

        For the moment, Stellarium+ doesn’t help to perform stars alignment, even though it would be a very nice feature in the future. As far as I know nexstar serial protocol doesn’t allow to perform alignment from a third party app. It seems to me that apps doing that need to control the DC Motors directly and completely by-pass the hand controller.

        In your case, I’d suggest you start with the easy path, and just keep your hand-controller for the moment.

        For the Stellarium Telescope Server, I’d suggest you just use the nexstar protocol instead, which is more flexible.


    • #521
      Jason Murphy

      Hello Fabien.
      Firstly I just want to say thanks for such a great product. I use Stellarium every day on my mobile and PC for telescope control.
      Can I ask, with the new Stellarium+ app does it connect via stellarium scope and eqmod?

      • #522
        Fabien Chéreau

        Hi Jason,

        thanks for the message!
        With Stellarium Plus you can connect to stellarium scope (or any other app compatible with the Stellarium Telescope Server Protocol) running on a PC connected to the scope.
        I don’t really know about Eqmod, but I don’t think it’s going to work with it.

        You can also connect directly to the mount using the serial protocol (NexStar or LX200 compatible), through a wifi module or a bluetooth module.

        For my tests, I also sometimes connect the mount to my computer using serial to USB cable, then create a TCP socket on my PC forwarding data to the serial cable. From Stellarium Plus (or any other app) it looks like a Wifi module was connected to the mount. If you want more info on this last setup, I can give you all socat / netcat commands to write.

        Best regards,


    • #552

      hello to everyone,
      I’m trying to use STEALLARIUM 0.19 to pilot my Skywatcher HEQ5 pro mounts with Synscan v3.39.05
      I follow every step indicated here:

      Stellarium is able to connect to the mount but, once I selected a target and I give the command ALT+1 or CTRL+1 NOTHING is happening.

      Do you know if I need to install ASCOM_platform, then STELLARIUMSCOPE, as sometimes I saw it’s susggested in some forums, oris there any solution for my problem.

      Best regards


      • #556
        Fabien Chéreau

        Hi Giampaolo,

        could you please attach some logs so that I can see what’s wrong? ALso trying with StellariumScope is not a bad idea, if you could report success or not.
        Finally, for questions related to Stellarium Desktop it’s better to ask us on our github page:


    • #576
      David Smalley

      Hello, I have enjoyed the Stellarium web page for years and actively recommend it at all of my outreach sessions. I recently purchased an IOptron AZ mount which has wifi built-in, but have absolutely no idea how to get Stellarium Mobile Plus on my android tablet to talk to it. Ioptron support recommends SkySafari, but your program is so much better.

      Any help/upgrade will be highly appreciated. And yes, I will test it immediately and thoroughly.

      David Smalley
      Homestead Astronomy (please feel free to join our faceboook page) (where you can see your Stellarium link under the menu item “The Sky”)

      • #581
        Fabien Chéreau

        Hi David,

        looking at this doc:

        It seems that you simply need to connect to the WIFI network created by the mount, and in Stellarium use a “Network” link type with the following parameters:
        IP Address:
        Port Number: 8899

        Let me know if it works!


    • #596

      hello i have enjoyed the stellarium web i how can create a atmosphere on stellarium web teach me the resource

    • #617
      Robert Chandler

      Hi Fabien, I just bought mobile+ and having trouble connecting to my telescope. I have a synscan wifi dongle, is there more detailed instructions?

    • #621
      Fabien Chéreau

      Hi Robert,

      for a SynScan controller, you need to connect to you wifi dongle using the official SynScan app. The Stellarium can talk to the SynScan app running in the background. Just use a “Network” link type, and set host and port 11882

      Best regards,


    • #624
      Jon Holliday

      Hi Fabien, I have just bought Stellarium Mobile Plus and using the above settings got connected, however when I align my scope the app shows it pointing to a different point in the sky. How do I correct this/

    • #625
      Jon Holliday

      Hi Fabien, managed to work out what was wrong. Re-set Mobile Plus to the correct time and all good. Looks a great app, am looking forward to some clear skies to try it out properly.

      Best regards,


    • #645
      Tim Sullivan

      Downloaded Stellarium Plus on my iPad but it will not connect. I have the wifi module for my Celestron AVX mount.


    • #680
      Dennis O’Farrell

      Wondering how to connect to my Mead ETX90. Should I get the Mead STELLA or other wireless dongle? Do I still need to go through a computer. Is there a serial cable option fo MacBook Air?

    • #823
      Johnny Olivares

      Having issues connecting to my Evolution.

      I did figure out the port and host but I get an error

      I was connected over wifi(tried both direct access and access point modes)

      doConnect, type: Network
      Host: Port: 2000
      Serial link status changed: connecting
      Serial link status changed: connected
      Identifying telescope controller…
      Trying NexStar…
      Ka => [255][0];[3][13][17][5][218];[5][17][13][5][22][135];;
      3][252][0][226] KaK*#[6]KaK*#[6]Ka
      K* => TRX timeout
      Trying LX200…
      Warning, started command with RX buffer not empty
      discarding RX buffer content: 75,42
      [6] :
      Can’t identify a telescope on serial connection

      • #856
        Fabien Chéreau

        Hi Johnny,

        I don’t think the celestron evolution wifi is supported in Stellarium. The protocol used is unfortunately a proprietary one..
        The only way to connect would be to use a regular Serial to Wifi or Serial to Bluetooth module, such as these ones:


    • #854
      Ian Cutler

      It is essential the correct time is set..This solves SynScan connection errors too.

    • #857
      Alec DiAstra

      I just emailed contact@stellarium-labs regarding a write-up i did in the CloudyNights forum about how to set this up using a TCP/USB bridge application.

      I would LOVE to see “direct” usb communications. The Celestron NexStar USB enabled scopes have a serial to USB adapter built in, so it should be pretty easy to communicate directly through the USB port on the mobile device to the telescope.

      I am pretty sure that SkySafari will also work in this way (TCP/USB bridge) and also allows for alignment. I think this is because Celestron is working directly with them.

      Using the hand control for alignment is not that difficult so its not a big deal.

      I do appreciate all the work that is going on here and hope that it continues. The more people know about options (which is why i did the write-up) the larger the user base will get.

    • #890
      Alec DiAstra

      So last night I tested scope control via stellarium. It worked but there were a few issues with alignment. I cant give great details at the moment but I will do some more scientific tests and data collection when i have another clear night. Clicking “GoTo” in the app and watching the scope start moving is quite exciting! I am using the Wired method but will probably experiment with Bluetooth soon.

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