Night Sky Quality Monitoring Report

Hovenweep NM, Utah

Hovenweep VC, June 5, 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	HOVE	Narrative: Site on hilltop north of Visitor Center, clear view of all horizons. Very warm, breezy. Seeing poor, transparency moderate, hazy in late afternoon. Clouds along horizons and occasional high clouds overhead, decreasing as night progresses (20% first set). Clouds illuminated in several places, especially near Cortez and Durango. Second data set extinction regression poor, presumably from high thin coulds. Many light domes visible, including Cortez/Durango, Farmington, Bluff, Blanding, and Monticello. An unusually bright dome, close by, identified with Montezuma Creek, may be oil and gas field facility. Sky degraded slightly, sky at zenith still quite dark.
Site Name	Hovenweep VC
Longitude	-109.07617
Latitude	37.3883
Elevation (m)	1606
Date (UT)	June 5, 2003
Time Start (UT)	7:40:28
Data Quality	Good
Equipment	Apogee, 35mmf/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	3
ZLM	6.6

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	7:40:28 8:29:54	0.262	0.049		-7.42	-6.89	20.14	21.71	PAN HEMI
2-Start End	8:53:53 9:42:30	0.240	0.150		-7.51	-6.98	20.12	21.59	PAN HEMI

LIGHT DOME DATA

City	Distance (km)	Azimuth	1st Data Set Brightness (mags)	Image
Cortez, CO	44	95.1	-2.12
Durango, CO	108	95.7
Farmington, NM	106	131.3	-0.81
Montezuma Creek, CO	25	236.0
Blanding, UT	44	306.4
Monticello, UT	58	337.0
Total			-4.26