Light Pollution Observations parser

I’ve created some code to do basic processing of light pollution observation files at

This came about from chatting to Prof. Brian Espey about processing the data from the SQM data loggers that he and others use around the country to monitor Irish dark skies and to assis the Dark Sky Places (and prospective places!).

Basically it does two things:

  • For the location in the header, work out the sun and moon altitude and filter the lines that meet the criteria we want. This is typically when the Sun is -18 degrees below the horizon and the Moon is -10 degrees below. (see )
  • Filter the lines that occur within an hour either side of local midnight. This is still a work in progress as ‘local midnight’ can mean a couple of different things. At the moment I take it to mean the solar antitransit time – he time during the night when the sun is transiting below the horizon. However this moves from night to night, but this may be the most useful from an astronomical point of view. However this won’t correlate well with human activity (think of a light that it timed to go off at a certain time each night), so we may add back in the ability to use local midnight as defined by the timezone, or fixed by the longitude from Grenwitch.

If you’re interested in contributing or just giving feedback/comments/requests please get in touch.

I’ve also got the lightmeter back up in Dalkey to get some more dark sky readings and hopefully see the impact of the LED streetlighting on sky brightness.

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