SQM-L sky brightness measurements

Since November 2010 we have performed sky brightness measurements with a SQM-L during most of our comet observing sessions.
Usually a first series was done near the start of a session, and another one near the end, but during short sessions only a single series was made.
The results are given in the table below. Each number is the average of at least 3 measurements, rounded to 1 decimal place.
Measurements were made near the zenith, but when denser parts of the Milky Way were overhead the SQM-L was pointed
slightly lower, but never below 70° altitude.
Factors that might have affected the sky quality are mentioned in the notes. Otherwise it can be assumed that measurements
were made when skies were clear without interfering clouds, moonlight or twilight.


Date (yyyy-mm-dd.dd)MagnitudeSiteNotes
2018-01-14.97021.3Burlage -
2018-01-14.87921.0Burlage -
2017-11-25.18821.1Sint Annen -
2017-10-21.91920.9Sint Annen -
2017-09-23.94120.9Sint Annen -
2017-09-16.95021.1Burlage -
2017-08-31.98521.2Burlage -
2017-05-27.96721.2Burlagegrey night; Sun 15.4° below horizon.
2017-05-20.98321.4BurlageSun 16.7° below horizon.
2017-05-20.94121.3BurlageSun 15.9° below horizon.
2017-05-14.92921.4BurlageSun 16.6° below horizon.
2017-04-29.95021.2Sint Annen -
2017-04-19.89020.9Sint Annen -
2017-04-15.87021.1Sint Annen -
2017-03-27.89521.3Burlage -
2017-03-27.85521.2Burlage -
2017-03-23.88421.0Sint Annen -
2017-03-21.91621.3Burlage -
2017-03-21.86021.1Burlage -
2017-02-24.92621.2Burlage -
2017-02-24.88121.0Burlage -
2017-02-14.79121.0Lauwersoog -
2017-02-13.78721.1Lauwersoog -
2017-02-04.02621.1Sint Annen -
2017-01-26.76021.0Lauwersoog -
2017-01-21.74921.1Lauwersoog -
2017-01-19.74820.9Lauwersoog -
2017-01-16.74521.0Lauwersoogground covered in snow.
2016-12-30.23821.1Sint Annen -
2016-12-06.18420.9Sint Annen -
2016-12-05.19420.9Sint Annen -
2016-11-28.20721.2Burlage -
2016-11-28.12821.4Burlage -
2016-11-27.84421.0Burlage -
2016-10-05.10821.2Burlage -
2016-10-04.89421.0Burlage -
2016-10-04.78820.8Burlage -
2016-09-13.06921.4Burlage -
2016-09-08.07021.3Burlage -
2016-09-07.87121.1Burlage -
2016-08-31.01321.3Burlage -
2016-08-30.88321.1Burlage -
2016-08-12.98321.1Burlage -
2016-08-06.94621.1Burlage -
2016-07-31.93621.3Burlage -
2016-05-09.02321.5Burlage -
2016-05-08.91721.4Burlage -
2016-05-04.93721.0Sint Annen -
2016-05-03.92921.2Sint Annen -
2016-05-01.96121.6Burlage -
2016-05-01.88521.2BurlageSun 15.9° below horizon.
2016-04-30.95521.1Sint Annen -
2016-04-28.92921.1Sint Annen -
2016-04-11.00121.7Burlage -
2016-04-10.92221.5Burlage16.6% illuminated Moon 1.4° over W. horizon.
2016-04-01.06921.2Sint Annen -
2016-03-17.13621.2Sint Annen -
2016-03-03.93521.2Sint Annen -
2016-02-29.89920.9Sint Annen -
2016-02-11.93921.1Sint Annen -
2016-02-11.01921.2Sint Annen -
2016-02-07.96921.1Sint Annen -
2015-12-31.88120.9Burlage -
2015-11-07.93520.8Sint Annen -
2015-10-12.07121.3Burlage -
2015-10-11.80221.0Burlage -
2015-10-10.80720.9Sint Annen -
2015-07-19.97020.9Sint AnnenSun 15.8° below horizon.
2015-04-19.90021.3Burlage -
2015-04-17.88620.9Sint Annen -
2015-04-16.89221.0Sint Annen -
2015-04-15.08921.2Sint Annen -
2015-02-18.78920.7Sint Annenslightly hazy conditions.
2014-11-10.75320.6Sint Annen -
2014-07-23.98320.8Sint AnnenSun 16.7° below horizon.
2014-05-19.96321.4BurlageSun 16.9° below horizon.
2014-05-18.94721.0Sint AnnenSun 16.3° below horizon.
2014-05-02.94621.1Sint Annen -
2014-04-20.87521.2Lauwersoog -
2014-03-12.16521.1Sint Annen -
2014-03-10.15021.1Sint Annen -
2014-03-08.16221.1Sint Annen -
2014-03-06.13421.4Burlage -
2014-03-05.94721.3Burlage -
2014-02-03.16521.3Burlage -
2014-02-02.92821.1Burlage -
2014-01-28.89621.0Burlageground covered in snow.
2014-01-28.82220.8Burlageground covered in snow.
2013-11-11.16021.1Burlage -
2013-10-01.12521.2Burlage 15% illuminated Moon 13° over E. horizon.
2013-09-30.84421.1Burlage -
2013-09-28.92421.2Burlage -
2013-09-28.81221.0Burlage -
2013-08-03.92621.2Burlage -
2013-07-17.98520.7Sint Annengrey night; Sun 15.7° below horizon.
2013-07-04.98120.5Sint Annengrey night; Sun 14.0° below horizon.
2013-06-04.98020.5Sint Annengrey night; Sun 14.2° below horizon.
2013-06-01.98020.8Lauwersooggrey night; Sun 14.5° below horizon.
2013-05-09.91821.0Sint Annen -
2013-05-05.89821.3Burlage -
2013-05-04.94021.0Sint Annen -
2013-04-30.96721.4Burlage -
2013-04-29.90421.1Sint Annen -
2013-04-28.89721.0Sint Annen -
2013-04-06.85621.3Burlage -
2013-04-02.84720.9Sint Annen -
2013-04-01.84121.1Sint Annen -
2013-03-13.00621.2Sint Annen -
2013-03-12.82220.8Sint Annen -
2013-03-04.79720.7Sint Annen -
2013-03-03.80820.9Sint Annen -
2013-01-03.88320.9Sint Annen -
2012-12-07.95321.0Burlageground covered in (thin) snow.
2012-12-07.84520.9Burlageground covered in (thin) snow.
2012-10-12.91520.8Sint Annen -
2012-10-11.90520.8Sint Annen -
2012-10-10.82820.7Sint Annen -
2012-10-07.87621.0Burlage -
2012-09-19.89821.1Burlage -
2012-09-09.92421.2Burlage -
2012-09-09.84921.0Burlage -
2012-07-23.97221.1BurlageSun 17° below horizon.
2012-05-26.97821.0BurlageSun 15.6° below horizon.
2012-05-24.99321.3BurlageSun 15.8° below horizon.
2012-05-16.97721.5Burlage -
2012-05-12.95121.4Burlage -
2012-04-26.91520.9Sint Annen5.6d Moon low in west
2012-04-24.93121.0Sint Annen -
2012-04-16.00221.6Burlage -
2012-04-15.87721.3Burlage -
2012-04-13.90421.0Sint Annen -
2012-04-12.90521.1Sint Annen -
2012-03-26.94721.0Sint Annen -
2012-03-22.99021.4Burlage -
2012-03-22.87521.0Burlage -
2012-03-19.93821.2Burlage -
2012-02-24.88520.9Sint Annen -
2011-11-27.98 20.9Burlage -
2011-11-27.85120.8Burlage -
2011-10-29.74320.7Sint AnnenSun 15.5° below horizon.
2011-10-24.10421.1Burlage -
2011-10-23.84020.9Burlage -
2011-10-22.85421.0Burlage -
2011-10-09.16620.8Sint Annen -
2011-10-01.83521.0Burlage -
2011-09-30.12121.3Burlage -
2011-09-29.92421.2Burlage -
2011-09-18.82420.8Sint Annenclose to moonrise.
2011-09-03.87821.1Burlage -
2011-09-01.87920.9Sint Annen -
2011-08-31.86520.9Sint Annen -
2011-07-06.98320.6Sint Annengrey night; Sun 14.1° below horizon.
2011-06-02.99620.9Burlagegrey night; Sun 14.5° below horizon.
2011-05-02.0021.7Burlage -
2011-05-01.9221.6Burlage -
2011-04-02.1221.1Sint Annenhaze near horizon.
2011-03-08.0221.6Burlage -
2011-03-07.9121.4Burlage -
2011-03-07.8421.1Burlage3.0d Moon 4° over W. horizon.
2011-01-29.0221.4Burlage -
2011-01-28.9321.3Burlage -
2011-01-09.9821.2Burlage -
2011-01-09.9221.2Burlage -
2011-01-03.0221.1Burlageground covered in snow.
2011-01-02.9821.2Burlageground covered in snow.
2010-12-13.0021.0Burlage -
2010-12-12.9520.9Burlage -
2010-11-07.9020.9Burlage -
2010-11-07.7920.9Burlage -