Starlight Cascade Sky Quality Meter

Page Created: 2005 July 21
Page Last Updated: 2021 December 14

The Sky Quality here is between 21.1 and 21.2 magnitudes/arcsec^2 (20050730 - 20050816)
20070716: 21.22 - no moon, clear sky)

Latest Data

Sky Quality Meter (SQM) readings (taken manually, hoping for a data logging SQM soon!) (high=darker):
  • Sunday 2020 Aug 16 22:30 EDT no moon, SQM=21.40
  • Saturday 2020 Aug 15 22:30 EDT no moon, SQM=21.39
  • Friday 2020 Aug 14 22:30 EDT no moon, SQM=21.40
  • Saturday 2018 Sept 15 03:30 EDT no moon SQM=21.48
  • Saturday 2017 December 16 18:05 EST SQM=20.59 after moonset
  • Monday 2014 August 25 21:30 EDT SQM=21.25 after moonset
  • Saturday 2013 April 27 unknown time SQM=20.91 after moonset
  • 2008 November 02 SQM=21.01


    We were at a meeting of the NYAA in the spring of 2005 in Toronto where Dr. Doug Welch from McMaster University talked about measuring light pollution using a custom built Sky Quality Meter. Being very interested in Responsible Lighting and Light Pollution (RASC-KC RASC IDA ), we purchased one, had it delivered shortly and started using it. The "Sky Quality Meter" measures the brightness of the night sky in magnitudes per square arcsecond. At a recent NYAA StarBQ Observing Session north of Cobourne, we tested our unit aside two others and got readings within 0.1 of each other.

    Mark 1

    Mark 2
    In early July 2005 our unit was recalled for a calibration error and another bug that surfaced during the beta testing, that of the exposed switch being pressed when in storage.
    We've received the Mark 2 unit, returned the Mark 1 unit and have started taking regular data.

    Some of the data tables items needed are: date, time, location, astronomical twilight time for that day, cloud cover, and the actual three readings (within one minute to track accuracy). Here is a Sample Data Recording Sheet in a small adobe acrobat file.

    With this data we hope to monitor the long term (years) Sky Quality (light Pollution) levels, possible short term (local lighting changes), provide a baseline of data for our location to compare to other locations.

  • Updates:
  • 2010 Oct 16 - we find that we are not using or recording the data nearly as much as we would like to anymore - some 5 years later. The data loggin SQM is looking nicer and nicer.

    Tips for use

  • Use after astronomical twilight (sun is more than 18 degrees below horizon before sunrise or after sunset)
  • aim right up at zenith
  • note cloud conditions and moon phase and position. Ideally there will be no cloud or moon when taking readings.

    Our RAW Data

  • Our Raw Data as of 20061021 in adobe PDF format.
    Please contact us if you want a copy of the data in spreadsheet format.

    Selected Data

  • Comparison of three units at NYAA Oak Heights Star night
    Date      Local Time UT Time Reading1 Reading2 Reading3  Average stddev Temp (C) Lat      Long
    20050702  21:50EDT           14.51    14.58    14.50     14.53   0.04   14      44.08.15N 77.58.40W
    20050702  21:50EDT           14.59    14.72    14.58     14.63   0.06   14      44.08.15N 77.58.40W
    20050702  21:50EDT           14.64    14.66    14.68     14.66   0.02   14      44.08.15N 77.58.40W
    20050702  21:50EDT           14.66    14.73    14.68     14.69   0.03   14      44.08.15N 77.58.40W
    20050702  21:50EDT           14.68    14.74    14.74     14.72   0.03   14      44.08.15N 77.58.40W


    Each of these references is printed out and carried in our 3 ring binder along with a few dozen datarecording sheets. We also have a smaller notebook to record data when we are away from our observatory.
  • Sample Data Recording Sheet
  • Frequently Asked Questions from the SQM website
  • Instruction Sheet for SQM

    Our Articles

    Sky Quality Meter Series:
  • SQM Results1 - Regulus 2006 October (71kb PDF)