Night Sky Quality Monitoring Report

Arches NP, Utah

Abbey's Ramada, June 3, 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	ARCH	Narrative: Site across main road from Balanced Rock, named "Abbey's Ramada" in honor of Edward Abbey's presence in 1950s mentioned in Desert Solitaire, on slickrock 200 feet north of dirt road (old entrance to Arches National Monument), near a pit toilet structure at this time, between the gravel dump and the main road. Level slickrock ideal for setting up equipment, but headlights from main road visible when cars come from north. Wind and sand a consideration at this site, somewhat exposed. Hazy, seeing fair, transparency fair. Light dome from Moab seems unusually bright, no direct glare, but Grand Junction faint, must be hazier to the east.
Site Name	Abbey's Ramada
Longitude	-109.5668
Latitude	38.70281
Elevation (m)	1537
Date (UT)	June 3, 2003
Time Start (UT)	6:24:26
Data Quality	Very Good
Equipment	Apogee, 35mm f/2, Bessel V
Observers	D. Duriscoe, C. Duriscoe, A. Richman
Air Temp (°F)	–
Rel Humid (%)	–
Wind Sp (mph)	–
CCD Temp (°C)	-25
Exp (seconds)	8
Bortle Class	3
ZLM	6.8

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	6:24:26 6:52:50	0.241	0.045		-7.44	-6.87	19.40	21.71	PAN HEMI

LIGHT DOME DATA

City	Distance (km)	Azimuth	1st Data Set Brightness (mags)	Image
Moab, UT	15	173.3	-3.91
Grand Junction, CO	98	63.8	-1.84
Total			-4.53