In astrophotography the combination of a goto mount, a camera and plate-solving is a powerful one. It allows you to do all kind of neat things, like polar-alignment without having a clear view of the south, extremely accurate goto functionality, and automated capture of multiple predefined targets.
There are roughly speaking three popular single-board-commputers (SBCs) that facilitate this: ASIAIR PRO, Stellarmate and and astroberry, in increasing order of technical complexity and reduction in price, with astroberry being free. Both Stellarmate and astroberry use the same underlying software, namely kstars/ekos and INDI Library.
Since both ASIAR and Stellarmate devices were out of stock, but Raspberry Pi 4s (rpi) aren't, I opted to try astroberry. Installation was straightforward, everything worked as advertised. To ease mounting I designed and printed an accessory collar that allows the rpi to be attached and removed easily.
|Raspberry Pi 4 in custom case mounted the accessory collar.|
The first issue with astroberry, and possibly also with Stellarmate, is that control is done via a remote desktop session over VNC. This isn't a problem other than the fact we are forced to use a desktop software on mobile device with very different aspect ratios and interaction paradigms. The end result is a very janky user experience. There are also concerns that, as the rpi uses passive cooling, it will quickly be thermally throttled, further degrading user experience unless one adds a cooling fan and heatsink.
So the next evolution is to run only the INDI server on the rpi and run kstars and ekos on a laptop, which provides a native desktop experience appropriate to the device and moves any heavy processing onto a more capable platform. This works, but does take away the main advantages of having a SBC, namely a small and light setup.
The next issue that arises is that of transfer time. Running kstar/ekos on a laptop means images captured by the rpi must be transferred before any additional algorithms, such as plate-solving, can run. With my Canon 800D it takes up to 15 seconds to transfer a single raw file over the built-in wireless. This is an unacceptable long amount of time.
The logical step is then to do away with the rpi altogether and run everything on the laptop I am using anyway. In this case a lenovo X220 with extended batteries. This works well, with transfer times of approximately one second.
As an aside, the default ekos layout doesn't do well on a display that is only 768px high, with many UI elements in the capture tab unusable. Setting ekos to have tabs on the left as opposed to at the top resolved this issue.
The current setup is thus:
- Canon 800D with 200mm F/2.8L II
- SmartEQ Pro+
- Lenovo X220 with KStars/EKOS/INDI
Now if only the clouds would go away I can actually see how this performs in anger.