Night Sky Quality Monitoring Report

Natural Bridges NM, Utah

Loop Drive Intersection, June 4, 2003

To effectively manage any resource, we need to know what we have and what we've lost. "Light Pollution", the brightness in the nighttime sky due to artificial light, can be seen from almost every park. The NPS has developed a system for measuring sky brightness to quantify the source and severity of light pollution. This system, developed with the assistance from professional astronomers and the International Dark-sky Association, utilizes a research-grade digital camera to capture the entire sky with a series of images. Data clearly shows that even remote national parks are not immune from stray artificial light. Sky brightness is measured in astronomical magnitudes in the V-band, abbreviated as "mags". The V-band measures mostly green light, omitting purple through ultraviolet and orange through infrared. The magnitude scale is a logarithmic scale. A difference of 5 magnitudes corresponds to a 100x difference in brightness. Lower values (smaller or more negative) are brighter. Further information on astronomical magnitudes can be found on this Sky and Telescope webpage. Data images are shown in false color, with yellow, red, and white corresponding to brighter sky and blue, purple and black corresponding to darker sky.

A more detailed explanation is available.

Category	Details	Image
Park	NABR	Narrative: The ONLY Bortle class 2 sky seen to date, no evidence of light domes from cities anywhere along the horizon. Horizons somewhat blocked to east, north, and west, however. Nevertheless, incredible detail in Milky Way, numerous dust lanes visible in Scorpius and Ophiucus. Lots of fire smoke drifting through confuses extinction measures, poor regression, and affects sky brightness measures somewhat. Transparency good, seeing good, warm, no wind.
Site Name	Loop Drive Intersection
Longitude	-109.98653
Latitude	37.6087
Elevation (m)	1975
Date (UT)	June 4, 2003
Time Start (UT)	6:39:30
Data Quality	Fair
Equipment	Apogee, 35mm f/2, Bessel V
Observers	D. Duriscoe, C. Duriscoe
Air Temp (°F)	–
Rel Humid (%)	–
Wind Sp (mph)	–
CCD Temp (°C)	-25
Exp (seconds)	8
Bortle Class	2
ZLM	7.1

SKY BRIGHTNESS DATA

Data Set Number	Time (UT)	Extinction Coefficient (mag/air-mass)	Std Err Y Extinction Stars (mags)	Zenith (mag/sq arc-sec)	Whole Sky (mags)	Sky Above 20° Altitude (mags)	Brightest (mag/sq arc-sec)	Darkest (mag/sq arc-sec)	Links to Sky Maps
1-Start End	6:39:30 7:07:26	0.160	0.088		-7.03	-6.54	20.35	21.95	PAN HEMI

LIGHT DOME DATA

City	Distance (km)	Azimuth	1st Data Set Brightness (mags)	Image
Total			-.34