Finally was able to get a clear night to try and fix my SG4 autoguiding. I redid the focus and calibration, I suspect it was entirely incorrect before (perhaps due to poor focus?) as the direction vectors seemed to have changed (I had not touched the scope). Certainly more promising now with no crazy jumpiness. I took a number of exposures with three conditions(PEC on in all cases): no autoguiding, low aggressiveness autoguiding (0.2) and aggressive autoguiding (0.5). I was using a blue filter to avoid saturation. I was careful to take a a set of exposures with replicates and capture autoguider images and log files, but I think the 10min exposures of each condition tell the main story. As you can see unguided was quite poor, low aggressive guided was better and I believe the autoguided was best (there were some intermittent high clouds near the end which I believe are responsible for the higher background and the lost star in the log file which is attached). The log file made sense, corrections appear sparse (as one would expect). I've also attached the initial image taken through the autoguider and the calibration file. Does the autoguided image (m13_blue_guided_agg-001_10.fit) look credible to people here?