Night Sky Quality Monitoring Report

Lassen Volcanic NP, California

Lassen Peak, July 16, 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	LAVO	Narrative: Site on south summit away from rock outcrop, not good for public or telescope, exposed, cold, windy. Smoke from forest fires in northern California visible at twilight in fine streaks, high in atmosphere. Seeing fair, breezy, transparency very good. Sky fairly bright from airglow, many cities visible from summit, nearby small towns below horizon so will not show up on data. Illumination to south greatest, combination of many cities. Zenith quite dark, much detail in Milky Way. Still a pretty dark site.
Site Name	Lassen Peak
Longitude	-121.50739
Latitude	40.48665
Elevation (m)	3172
Date (UT)	July 16, 2004
Time Start (UT)	6:33:27
Data Quality	Excellent
Equipment	SBIG 50mm f/2 6084
Observers	D.Duriscoe, J. Arnold
Air Temp (°F)	45
Rel Humid (%)	9
Wind Sp (mph)	15
CCD Temp (°C)	-20
Exp (seconds)	15
Bortle Class	3
ZLM	6.9

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	6:33:27 6:53:44	0.117	0.040	21.41 21.42	-7.61	-6.98	19.59	21.52	PAN HEMI
2-Start End	7:16:46 7:37:10	0.117	0.046	21.41 21.43	-7.58	-6.93	19.64	21.67	PAN HEMI
3-Start End	8:00:14 8:20:49	0.115	0.044	21.44 21.36	-7.49	-6.80	19.69	21.72	PAN HEMI

LIGHT DOME DATA

City	Distance (km)	Azimuth	1st Data Set Brightness (mags)	Image
Redding	73	277.7	-2.49
Yuba City	150	183.3	-3.60
Chico	85	197.5
San Francisco, CA	312	197.2
Sacramento, CA	213	179.1
Reno, NV	178	125.6	-1.94
Total			-4.31