Night Sky Quality Monitoring Report

Lake Mead NRA, Nevada

Government wash view, December 3, 2004

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	LAME	Narrative: Site on viewpoint just west of Government Wash, parking area with short walk to hilltop. Not good for public or telescopes, too close to main road. Sky very bright from light pollution, landscape illuminated to first quarter moon levels. Milky Way nearly invisible, only brightest portions near zenith are seen. Seeing good, Transparency good. No clouds.
Site Name	Government wash view
Longitude	-114.83375
Latitude	36.15171
Elevation (m)	423
Date (UT)	December 3, 2004
Time Start (UT)	2:35:37
Data Quality	Excellent
Equipment	SBIG 50mm f/2 6084
Observers	D.Duriscoe, C. Duriscoe
Air Temp (°F)	43
Rel Humid (%)	34
Wind Sp (mph)	3
CCD Temp (°C)	-20
Exp (seconds)	15
Bortle Class	6
ZLM	5.8

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	2:35:37 2:55:51	0.159	0.043	19.96 19.95	-9.79	-8.65	15.62	20.12	PAN HEMI
2-Start End	3:13:52 3:34:05	0.154	0.048	19.97 19.96	-9.78	-8.65	15.62	20.12	PAN HEMI
3-Start End	3:52:07 4:12:20	0.160	0.045	19.96 19.96	-9.78	-8.65	15.63	20.10	PAN HEMI

LIGHT DOME DATA

City	Distance (km)	Azimuth	1st Data Set Brightness (mags)	Image
Boulder City, NV	21	181.1	-9.57
Henderson, NV	20	229.3
Las Vegas, NV	36	279.8
Total			-9.69