All these versions of ScopeDog are a way of marking significant developments in the design and functionality.
A recap of versions so far.
mk1 - almost 10 years old now. Built around now obsolete Phidget modules, built in GPS, Pi3 and code written in Java.
mk2 - First appeared in 2021. New Phidget modules allowed a re-packaging into a much smaller box. Pi4 running code in Java. Closer intregration with the Nexus DSC meant no GPS needed.
mk3 - 2022. Same basic hardware as mk2 but code now in Python. Digital finder functionality built in. New hand paddle with OLED display and digital finder controls. Vastly improved pointing accuracy and ease of initial alignment.
So why a mk4?
Based on experiences with the mk3, I could see the potential to remove the need for mount encoders completely. The digital finder can quickly determine absolute telescope position and the drive stepper motors can manage position inbetween solves.
With a week confined to a caravan at a rainy astro camp, the code rewrite made good progress. Currently I can just power up the scope, point it at an object, and 3 seconds later it is tracking. No alignment needed! I can then do a goto to a new target, which is initially accomplished using stepper motor step counts, but once that is done, a plate-solve automatically corrects any errors and puts the scope on target. Adds about 4 seconds to a goto.
Only about 10% of the core code needed rewriting, but the most difficult part was establishing a direct wifi link to SkySafari (previous this had been left to the Nexus DSC)
