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Back in May, I posted a question about refocussing meteor cameras.
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…
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Hi Dominic,
intereresting to see this effect plotted on a chart.
is this with or without the masking tape applied to the bezel, as suggested in the previous thread?
Best regards
William
That is without masking tape, so the graph is basically justifying that your suggestion in May was correct! 🙂
I made my post in May immediately after refocussing my camera, and have only just got around to opening it up again and looking for a more permanent fix.
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.
regards Stan.
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