As those of you who follow my astroimaging journey know, I am a fan of low cost solutions, recycling and re-purposing old equipment. I'm certainly not an inventor, but I enjoy adapting ideas and solutions that others have developed (with appropriate credit I hope) to fit my equipment and suit my needs. I enjoy the challenge, although am becoming less tolerant of the frustrations as I get older. My Raspberry Pi project is one such example...

I'm not a programmer (although would quite like to learn, and Raspbian Debian looks manageable), so decided on Jasem Mutlaq's Stellarmate OS, available as a complete image file, bundled with EKOS astroimaging suite and Kstars planetarium, and including a handy iOS App for my iPad. Developed using open source tools, and designed to be an 'internet of things for astrophotography', it can be used with a range of equipment supported by the the INDI library. Other solutions such as the renowned ASIair pro device are restricted to ZWO cameras and equipment.

The Pi works flawlessly, although tends to run hot - I bought the 8GB RPi4 as part of a kit with a simple plastic enclosure (minimal effect on WiFi range), a mains transformer (5v 3A essential), HDMI cable and added a 256 GB SD card which I flashed with Stellarmate OS (£49). EKOS/Kstars works well, and is easy to learn, with many powerful features inbuilt - polar alignment assistant, autoguiding, focus, astrometry, capture, sequence etc. Perhaps the weakest link is the App, which can be temperamental, but is improving with every new release. With access via VNC or a PC running EKOS this is not essential but does add to the portability and simplicity of the setup. Stellarmate has it's own hotspot or can connect into my home network (via WiFi or Ethernet).

I have managed to get this working with my Star Adventurer 2i, and it has native drivers for my Altair hypercam 183C and even an INDI driver for my old Meade IIC camera, allowing me to pulse guide the mount (it also supports ST4 although the drivers for my Orion SSAG are flaky). Astrometry is superb, allowing me to fine tune my location, and although I do not have 'GoTo', it allows accurate 'PushTo' and framing of objects. Currently focusing is manual, but works, and I can use the PAA to fine tune my Polar alignment. Tracking and capture work well, allowing sequencing of lights, darks, flats and biases (all of which could be automated with the right kit). The only thing I'm really missing is clear nights!

I've attached some images in the revisions - all fairly short exposures, but I'm happy with the potential. I'm currently using PHD2 to pulse guide and need to see if I can tweak the settings to improve this (to date I have found it more reliable than the internal guider software). The Pi is an exercise in patience, everything takes a bit longer, and as mentioned the App can be flaky at times, but, for such a tiny gadget I'm amazed at what it can do, and the potential it offers. I'm already planning to add a motor control HAT, and stepper motors for autofocus and to provide basic declination guiding.

For those of you who have got to the bottom of this, and are thinking OK, but why not just get out there and buy an HEQ or similar smart GoTo mount, and off the shelf autofocus... my response 'where would be the fun in that', although I don't mind saying it is an attractive option sometimes!