GLOBE at Night

an Opportunity for Citizen-Scientists to Monitor Light Pollution Worldwide

GLOBE at Night

GLOBE at Night is a fun, international citizen-science event that encourages everyone— students, educators, dark sky advocates and the general public— to measure the darkness of their local skies and contribute their observations online to a world map. The program is a centerpiece of the Dark Skies Awareness Global Cornerstone Project for the International Year of Astronomy (IYA) in 2009. Its goal is to raise public awareness of the impact of artificial lighting on local environments by getting people involved. Data collection and online reporting is simple and user-friendly.

GLOBE at Night 2008 results

Led by the educational outreach staff at the National Optical Astronomy Observatory and UCAR’s GLOBE Program, the GLOBE at Night campaign will take place for a 4th year from March 16-28, 2009. Over the past 3 years, tens of thousands of citizen-scientists around the world have contributed measurements of their local sky brightness to a growing global database in two ways: simple unaided-eye observations toward the constellation Orion and quantitative digital measurements through a handheld, well-calibrated sky-brightness meter. For the first method, citizen-scientists take data on light pollution levels by comparing what they see toward Orion, with star maps showing different stellar brightness limits. The basic idea is to look for the faintest stars and match them to one of seven star maps of progressively fainter limiting magnitudes. For the second method, digital sky-brightness meters are used for more precise measurements. The low-cost digital Sky Quality Meters (SQM-Ls), manufactured by Unihedron of Ontario, Canada, can make a highly repeatable direct measurement of integrated sky brightness. The newly available second-generation of SQMs being used this year by several GLOBE at Night sites has a cone-shaped “field of view” that is three times more narrow than the older model. This specifically aids its use in city environments, where surrounding lights or buildings may affect the readings. Reporting is also on-line.

To learn the five easy steps to participate in either type of GLOBE at Night program and to obtain important information on light pollution, stellar magnitudes, the mythology of Orion, how to find Orion, how to obtain your latitude and longitude, and how to use an SQM, see No prior experience is necessary. All information needed to participate is on the GLOBE at Night Web site, along with downloadable activity guides available in six languages. All observations will be available online via Google Earth and as downloadable datasets.

Utilizing the international networks of its partners, GLOBE at Night is able to engage people from around the world. From 2006-2008, GLOBE at Night successfully conducted two-week campaigns each spring, during which a total of 20,000 observations were been submitted online from 100 countries from around the globe. Within a few weeks after submission, a world map showing the results is available. These measurements can be compared with data from previous years of GLOBE at Night, as well as with satellite data, population densities, and electrical power-usage maps. Data from multiple locations in one city or region are especially interesting, and can be used as the basis of a class project or science fair experiment, or even to inform the development of public policy.

GLOBE at Night 2008 results

As an example, Figure 2 shows results for Tucson from GLOBE at Night 2008. Tucson is a city in which there are about a half a million residents proper and more than three-quarters of a million people in the greater area. Light pollution is a major concern in a city of this size. Limiting magnitudes as observed toward Orion are plotted against the population density for Tucson from the latest census (in 2005).

GLOBE at Night 2008 results

The same limiting magnitudes are also plotted in Figures 3 with respect to the “Lights at Nights” as seen from the DMSP satellite data from NOAA. The legend shows a series of monochromatically colored dots that represent the limiting magnitudes as observed toward Orion. The lighter in color the dot appears, the brighter the sky. If the faintest star you can see is a Magnitude 1 star, you are either standing below a streetlight, or your city has serious light pollution issues.

More measurements made each year and over the next few years will allow for more in depth analysis. More measurements within a city will provide maps of higher resolution. Comparisons between years would allow people to monitor changes. Monitoring our environment will allow us as citizen-scientists to identify and preserve dark sky oases in cities or catch an area developing too quickly and influence people to make smart choices in lighting. Monitoring our environment might allow us to track the habitats of animals endangered by over-lighting. If more and more people took a few minutes during the March 2009 campaign to measure sky brightness either toward Orion with the unaided-eye or toward zenith with a Sky Quality Meter (or both!), their measurements will make a world of difference.

The goal for GLOBE at Night 2009 will be to get more people to canvas a city with measurements at as many locations as possible during the March 16-28 campaign. For instance, between a few schools in a city, 1000 measurements (of at least a km apart) could reasonably be made within a 40 square kilometer area in less than two weeks. There will be an opportunity to apply for limited funding to buy either Sky Quality Meters or software for follow-up analysis. Persons or groups interested in obtaining funding will be able to apply on the IYA Dark Skies Web site before 2009.

Night Sky Network Presentation

For more information on GLOBE at Night and how you can get involved, listen to a presentation given via telecon by Connie Walker from the National Optical Astronomy Observatory to the Night Sky Network of Amateur Astronomy Clubs. The presentation is in two parts:

  1. Audio of the telecon [54 MB mp3 file]
  2. Presentation Slides:

Happy star-hunting!