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Measuring sky brightness during a solar eclipse with CHDK.

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Offline vostok

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Measuring sky brightness during a solar eclipse with CHDK.
« on: 24 / December / 2010, 18:45:04 »
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Hi,

There's a partial solar eclipse coming up 2010-01-04 which will be visible in Europe. A friend of mine will be beyond the artic circle during the eclipse and will have the sun reaching an altitude of only around -2 degrees at noon on eclipse day. So I proposed maybe he would have luck observing the eclipse with using CHDK to record variations in twilight sky brightness.

I've recorded illuminance values on a few eclipses now and the results look nice. I suppose some of you might find this interesting too? Please conduct measurements and report the results to me if you do. The script we use takes two parametres: the interval of brightness sampling and the count for which the images are taken while sampling (e.g. a shot taken once per five measurements). So you'll get a nice time lapse movie too.

If you want the dimming to be visible in the timelapse too, you have to use P-mode in order for the exposure meter to work and force constant exposure settings via CHDK overrides (meter some decent values prior to starting the script). Ideally, a reference measurement of a day with no eclipse (the day before or after) is needed.

The script is linked in the first post of the project thread at the finnish astronomical association Ursa's forum: http://foorumi.avaruus.fi/index.php?topic=7632.0

If you're interested in our babbling, maybe you'll have luck with google translate, or you can post your questions in this thread.

Lauri
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