Night Sky Quality Monitoring Report
Great Sand Dunes NP, Colorado
Buffalo Ranch, November 6, 2005
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 | GRSA |
 Narrative: Site in Southwest corner of park, on road to Nature Conservancy Buffalo ranch, on west side of graded road about 1 mile north of highway. Sand everywhere, not good for public or telescopes, parking lot of VC or campground would be much better. Site chosen to reduce horizon blocking from Sangre de Cristo Mts. to east and north. Hazy in evening, clearing as night progresses. Clouds over mountains gradually diminshing, 15% on first set, less than 5% on last, reflecting lights of Denver and Colorado Springs, light dome calculations inaccurate. Lights of Alamosa and a string of "farm lights" along the highway north of Alamosa affect night vision, direct glare. Aside from glare from farm lights, sky quite dark, gegenschein visible, glow to northeast from Denver and Colorado Springs extends only to about 15 degrees.
|
| Site Name | sw corner | |
| Longitude | -105.68771 | |
| Latitude | 37.66694 | |
| Elevation (m) | 2306 | |
| Date (UT) | November 6, 2005 | |
| Time Start (UT) | 5:50:04 | |
| Data Quality | Good | |
| Equipment | SBIG 50mm f/2 6048 | |
| Observers | D.Duriscoe | |
| Air Temp (°F) | 30.5 | |
| Rel Humid (%) | 30 | |
| Wind Sp (mph) | 2 | |
| CCD Temp (°C) | -20 | |
| Exp (seconds) | 12 | |
| Bortle Class | 3 | |
| ZLM | 6.7 |
| 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 |
5:50:04 6:07:29 |
0.137 |
0.045 |
21.66 21.59 |
-7.35 |
-6.71 |
19.88 |
21.70 |
PAN HEMI |
| 2-Start End |
6:47:03 7:04:27 |
0.126 |
0.041 |
21.48 21.46 |
-7.43 |
-6.80 |
19.93 |
21.57 |
PAN HEMI |
| 3-Start End |
7:44:01 8:01:26 |
0.130 |
0.048 |
21.43 21.42 |
-7.45 |
-6.80 |
19.94 |
21.55 |
PAN HEMI |
| City | Distance (km) |
Azimuth | 1st Data Set Brightness (mags) |
Image |
|---|---|---|---|---|
| Alamosa | 27 | 216.7 | -2.33 |
 |
| Denver, CO | 144 | 16.7 | -1.22 | |
| Colorado Springs, CO | 156 | 31.2 | -2.08 | |
| Pueblo, CO | 115 | 54.0 | -1.74 | |
| Total | -3.61 |