Starlight Cascade Sky Quality Meter
Page Created: 2005 July 21
Page Last Updated: 2010 October 16
The Sky Quality here is between 21.1 and 21.2 magnitudes/arcsec^2 (20050730 - 20050816)
20070716: 21.22 - no moon, clear sky)
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
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.
We've received the Mark 2 unit, returned the Mark 1 unit and have started
taking regular data.
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.
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.
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.
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
Instruction Sheet for SQM
Richard Berry's Study "LIGHT POLLUTION IN SOUTHERN ONTARIO"
THE JOURNAL OF THE ROYAL ASTRONOMICAL SOCIETY OF CANADA
Vol. 70, No. 3 JUNE 1976 Whole No. 540
Sky Quality Meter Series:
SQM Results1 - Regulus 2006 October (71kb PDF)