Meteor camera focus

[Dominic Ford]

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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   fov.png
   

[William Stewart]

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

[Dominic Ford]

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.

[stan armstrong]

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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