Tuesday, 7 January 2025

Distributed telescope control via Ethernet over mains with a headless Linux computer attached to the telescope, controlled remotely by AstroDMx Capture.

While Nicola is refactoring the AstroDMx Capture code, we have been testing  a system for remote control of an imaging system via a distributed system using Ethernet over mains

List of equipment

  • Celestron AVX mount
  • Stella Mira 66 ED APO refractor
  • ZWO Electronic Focuser
  • ZWO Electronic Filter wheel
  • SVBONY SV 605MC 14 bit Cooled CMOS camera
  • SVBONY SV165 Guide scope
  • QHY-5II-M guide camera
  • MeLE Quieter 2D fanless mini PC running Fedora Linux
  • TP-Link LS108G 8 Port Gigabit Network Switch
  • Tenda P200 x 2 Powerline Ethernet adapters
  • JJC DHS-1 USB Lens Heater Strip x 3 (For imaging scope, guide scope and ZWO electronic focuser)
  • Multi USB 4 Port Plug Adaptor
  • 5A 12V Power adapters x 3 (For mount, Cooled CMOS camera and Lens Heater Strips)
  • Mains extension lead

The equipment in use


A distributed system is a network of independent computers that work together. These systems share resources, data, and tasks across multiple machines.

The schematic diagram bellow shows the connectivity between all devices involved in our setup. At the telescope, there is a small headless computer (In our case a MeLE Quieter 2D fanless mini PC) running Fedora Linux. This computer runs an INDI (Instrument Neutral Distributed Interface) server which is responsible for managing the states of all of the connected astronomical devices. There is no client software running on this system and hence the telescope computer is not accessed via VNC or RDP. Using desktop sharing protocols over slow networks often introduces UI lag which can be awkward to use. 

The small headless computer is connected via Ethernet to a powerline adapter which is paired with a matching powerline adapter indoors. This link forms a reliable and encrypted Ethernet connection between the powerline adapters and thus allows the small form factor computer to be accessed by its IP address from any computer on the local network. 

AstroDMx Capture is run on the capture computer connected to the local network and can access all of the devices in a similar fashion to how they would be if they were connected directly via USB. PHD2 auto-guiding software is run on the guide computer. This essentially creates a distributed system.

Schematics of the system used

The imaging computer and the guide computer are both located indoors along with the ethernet switch and one Ethernet power adapter which is plugged into the mains. We use two separate computers for convenience of divided activities between two people, but just the imaging computer could have been used alone, doing the tasks of both computers. The imaging computer runs AstroDMx Capture and the Guide computer runs PHD2 guiding software. We work this way because we are always testing the current development of AstroDMx Capture, and we prefer to monitor the session at all times.

The rest of the equipment is located outdoors at the observing site at the front of the house or in the observatory area at the top of the rear garden. All that connects them is a mains extension lead.

Screenshot of AstroDMx Capture capturing monochrome luminance data on M33 The Triangulum galaxy


30 minutes worth of 5 minute exposures was captured through each of: Red, Green, Blue, UV/IR cut and H-alpha filters.

The data were stacked and co-registered in Deep Sky Stacker. Further processing was done with Siril, PixInsight, Gimp 2.10,  Starnet, ACDSee and the Seti Astro Cosmic Clarity suite combining all of the data into the final image.

Final image of M33


The advantage of this system is that the imaging and guide computers access the relevant equipment via the headless computer exactly as though they are directly connected by USB and no desktop sharing software is used. Currently we use an INDI server, but in the future, INDIGO and ASCOM Alpaca will be available. Of course, all of this takes time but will be greatly facilitated by Nicola's current refactoring work.