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Dedicated observatory PC - Pi4 8G


discardedastro

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So, for a good long while - going on 3-4 years - I've been using a spare laptop as my observing control PC for imaging. However, if I ever get around to an observatory I'll need something full-time and the laptop takes up a lot of space to have out all the time.

I figured I could do pretty well with the Pi4 so set about making an ideal "Obsy in a box" setup. This comprises:

  • Pi4 8G - 4G probably more than enough but best to futureproof
  • ArgonONE case - an excellent, passively-cooled (but fan-assisted, i2c controlled) aluminium case, with...
  • ArgonONE M.2 SATA to USB adapter - a nice way to expose a SATA (not NVMe!) M.2 disk to a Pi in a neat case
  • WD Blue 500G SATA M.2 drive - for storage without write-cycling the uSD card to death
  • 2.5A 5V adapter to power it all via USB-C

This all packages very neatly into a box that lives in my "comms cupboard" next to the network switches/routers. The Pi is networked into the core on 1GE copper, which gives it a nice fast path to the storage array (a 16-disk 30TB ZFS RAIDZ3 in the garage) that acts as primary archival storage for the imagery.

I didn't go down the Astroberry etc pre-made stacks as I like to run "current" versions of software (though stable) and Arch is very flexible and lightweight, enabling a very small footprint.

Software-wise I wanted fully headless but to run KStars/Ekos natively for remote control of the Pi on the 'scope running INDI. This turned out to be pretty straightforward:

  • Arch Linux - I've been using Arch for many years now and it's a rolling release with a great community of INDI/astro users so excellent KStars etc support following the main release cycle
  • TigerVNC, set up as per https://wiki.archlinux.org/index.php/TigerVNC#Running_vncserver_for_virtual_(headless)_sessions
  • KStars/Ekos - I copied my ~/.indi and ~/.local/share/kstars folders across which got all my main configuration, and just had to rebuild the phd2 darks library
  • LXDE as a lightweight desktop environment - GNOME was a non-starter

This gets me a user-bound VNC virtual desktop that performs well enough to be usable interactively at 2560x1440px.

1188511352_2021-02-1821_05_54-Stellarium0_20.2.thumb.png.d88b4d034c7be87d68fab7e7c483ffef.png

VNC is definitely the bottleneck when looking at interactive media like KStars full screen - actually encoding the frames to ship over the LAN takes up a bunch of time and isn't thread/CPU-bound so not sure what's going on there. But when using KStars et al windowed, as above, it works pretty smoothly and responsively.

I use the SATA disk as local capture storage for KStars/Ekos, and then I use rsync to push this across during daylight hours to the storage array, from where I can pull it down for PixInsight.

All KStars/Ekos functions and PHD2 perform beautifully and promptly, and there's no threat of CPU-bound performance snags - running an imaging session I have a load average of ~1.2 and only 1.4G of RAM in use (though a good 3G of RAM is acting as a file cache, which undoubtedly helps things like plate solving etc).

All in all it's working remarkably well and has completely replaced my laptop in a tiny footprint! Very pleased with the result and shall work now on monitoring and some status displays around the house.

Edited by discardedastro
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Great result! What's not to like :)

 I went down the RasPi 4 and Astroberry route a while ago but unfortunately something at hardware/software level wasn't working for me. I was desperately disappointed. Such a neat solution and I really liked Ekos too. 

I've tried a mini PC at the mount running Ubuntu to retain the Ekos environment but that too was unstable for me  so I'm back to Windows and APT (which I also like!). Still using RealVNC though. I think it's great as I can use my ancient Chines android tablet at the scope or my W10 from the lounge. VNC does seem to lag quite often but not enough to spoil anything.

I never fully diagnosed my issues with the RasPi. Maye one day I'll return to it, but for now I've got bigger fish to fry...

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1 minute ago, Paul M said:

I went down the RasPi 4 and Astroberry route a while ago but unfortunately something at hardware/software level wasn't working for me. I was desperately disappointed. Such a neat solution and I really liked Ekos too. 

I've tried a mini PC at the mount running Ubuntu to retain the Ekos environment but that too was unstable for me  so I'm back to Windows and APT (which I also like!). Still using RealVNC though. I think it's great as I can use my ancient Chines android tablet at the scope or my W10 from the lounge. VNC does seem to lag quite often but not enough to spoil anything.

I should add that the telescope has a Pi 4 on it (mounted in a little case on the tube of the 200P with velcro tape) running INDIserver which is the "other half" of the equation - this has been running flawlessly for a couple of years.

I used to run Windows/APT and then SGP back in the day but kept coming back to Linux for the remote management and monitoring. RDP is definitely better than VNC, which is the big "win" over Linux for remote operations, but everything else I really do prefer Linux. Ekos/KStars has come a very long way over the years, too.

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