Sky Quality Monitoring Program

A joint initiative of the Maria Mitchell Association and Nantucket Lights

Using Sky Quality Meters, we are monitoring the darkness of our night sky, thanks to some dedicated volunteers and the financial support of the Maria Mitchell Association.

The measurements taken under this program will allow comparison of the sky brightness at different places on the island and document the amount of light pollution that exists and its evolution over time so that the effectiveness of efforts to mitigate light pollution can be assessed.

The measurements can also be used to support an application to DarkSky International (formerly known as the International Dark-Sky Association) for certification of Nantucket as an “International Dark Sky Community” under its International Dark Sky Places Program. Having a Sky Quality Monitoring Program is one of the requirements for that.

The measurements are taken when there is a new moon and thus no moonlight -- following the Globe at Night schedule below -- so that any brightness of the sky is due to artificial light at night rather than moonlight.

NOTE: For the photo, a light was turned on to make our volunteer visible. The light was off when the meter reading was taken.

Our Monitoring Locations

For purposes of qualifying for International Dark Sky Community status, measurements are taken at the eight locations shown on this map:

(1) Nantucket Town; (2) Madaket Beach; (3) Nantucket Elementary School; (4) Nantucket Airport; (5) Altar Rock; (6) 'Sconset; (7) Wauwinet; and (8) Surfside Beach.

These locations were chosen to include a mix of sites likely to have relatively bright and dark nighttime skies. The average of the readings at all eight locations will be used as the reading for the island as a whole.

Supplemental Data:

Starting in August 2024, we started collecting data at a ninth location (Cisco Beach) to supplement the data collected for Dark Sky Community certification.

Baseline: First Year of Data

The first year of collected data (June 2022 through May 2023) showed that the island average was 20.65 on the SQM scale. The point at which the Milky Way is difficult or impossible to see with the naked eye is approximately 20.2 on that scale. (As this diagram illustrates, the higher the number on the SQM scale, the darker the night sky is, and the less light pollution there is.)

Our goal is reduce light pollution so that the island average is at 21.0 — or even higher!

Globe at Night 2025: Can you see the stars?

Every year, the Globe at Night international community science campaign, a program of NSF’s NOIRLab, raises awareness about the impact of light pollution by inviting community scientists

around the world to measure and submit night sky brightness observations.

All you need is a computer, tablet,or smartphone!

How to Participate:

During the campaign dates (see above), go outside on a clear night more than an hour after sunset and let your eyes adjust to the dark (at least 10 minutes).

Find the constellation you are reporting on. Many smartphone apps or programs can help you locate it if you are unsure where it is.

Go to the Globe at Night report page, make sure you are in nighttime mode, and enter your data.

Choose the star chart that most closely matches what you see in the sky.

Select the amount of cloud cover at the time of your observation and submit your data.

You can find more detailed instructions and the list of constellations here

and learn more about Globe at Night on their website.