A couple of days ago I noticed that the focus of my camera was getting quite soft again, and gave it another round of refocusing.
I was wondering whether the hot weather had made it go out of focus, and to test this I had a look back at the past data. I’m using a cheap zoom CCTV lens, so I tried plotting a graph of the field-of-view of the camera over time. This graph is calculated by using astrometry.net to plate-solve the camera’s images each night. Each red dot represents a single clear night when I was able to record enough stars to get a fix on the camera’s pointing.
Seems to be an interesting long-term trend here. I guess my camera is going out of focus because the daily temperature cycling (or possibly vibration) is causing it to very gradually zoom in. Possibly I should glue the zoom control…
On original reading Dominic i assumed a costly academic set up, hence delighted to read now it was a ‘ cheap zoom CCTV lens’ . I vaguely remember mentioning having similar problems with the dominance being a North to South changeover in View. Recently with the Cooler evenings it would seem that Temperature may well be affecting my images too. I like the idea of your graphic representation of the issue, althoughin my case there is no easy access to the Lens. Will be interested to follow your progress.