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Chelmsford sky brightness

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About this observation
Observer
Nick James
Time of observation
02/11/2017 - 08:41
Object
Sky
Observing location
Chelmsford
Equipment
C11 + FLI CCD
Exposure
5s
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I did a long photometry run last night on a possible microlensing candidate. One of the outputs from my image processing pipeline is the instrumental sky brightness and this is plotted here. The plot show a clear drop at 01:00 UTC corresponding to the local streetlights going off. It also shows my darkest skies are between 04:00 and 05:00. The lights come back on again at 5am, but more slowly than they go off since most are still LPS and HPS types although LEDs are getting more common around here. This plot is not corrected for the star's altitude which was at its highest around 02:20UTC.

Comments

Peter Carson's picture

Hi Nick,

That's very interesting. My measurements using a handheld SQM meter back up your findings. My sky is darkest around the period 03.00hrs to 05.00hrs. My local LED street lights dim between 12.00hrs and 05.00hrs but the biggest effect is from general outdoor lighting, advertising, traffic and domestic security lighting that appears to go off in the later part of the night together with streetlighting in more distant areas that, like yours, goes out between  01.00hrs and 05.00hrs.

Peter

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