Night Sky Quality Monitoring Report
Joshua Tree NP, California
Keyes View, December 5, 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 | JOTR |
 Narrative: Very windy, gusts to 25 mph. High clouds coming and going to south and west, maximum 10‰ cover, 3rd set most clould-free. Direct lights from Indio and Coachella Valley strike the actual viewpoint. Site moved to near the weather station just east in saddle so that land blocks direct glare from lights in the valley. Sky very bright to southwest from light pollution, Milky Way barely visible to west, easily visible overhead and to east. Light from the sky illuminates land to fat crescent moonlight levels. View parking lot good for public and telescopes, but very bright compared to other locations in the park.
|
| Site Name | Keyes View | |
| Longitude | -116.17375 | |
| Latitude | 33.92514 | |
| Elevation (m) | 1524 | |
| Date (UT) | December 5, 2005 | |
| Time Start (UT) | 5:04:41 | |
| Data Quality | Excellent | |
| Equipment | SBIG 50mm f/2 6084 | |
| Observers | D.Duriscoe | |
| Air Temp (°F) | 32.2 | |
| Rel Humid (%) | 22 | |
| Wind Sp (mph) | 13 | |
| CCD Temp (°C) | -20 | |
| Exp (seconds) | 12 | |
| Bortle Class | 5 | |
| 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 |
5:04:41 5:22:09 |
0.136 |
0.050 |
21.34 21.33 |
-8.12 |
-7.15 |
17.79 |
21.42 |
PAN HEMI |
| 2-Start End |
6:02:44 6:20:11 |
0.134 |
0.044 |
21.31 21.28 |
-8.09 |
-7.13 |
17.45 |
21.38 |
PAN HEMI |
| 3-Start End |
7:00:45 7:18:11 |
0.132 |
0.048 |
21.23 21.09 |
-8.10 |
-7.15 |
17.10 |
21.33 |
PAN HEMI |
| City | Distance (km) |
Azimuth | 1st Data Set Brightness (mags) |
Image |
|---|---|---|---|---|
| Twentynine Palms |
26 | 22.8 | -3.09 |
 |
| Las Vegas, NV | 267 | 18.7 | ||
| El Centro | 139 | 155.5 | -3.47 | |
| Palm Springs | 37 | 243.3 | -7.19 | |
| San Diego, CA | 152 | 216.3 | ||
| Los Angeles, CA | 208 | 276.4 | ||
| Total | -7.26 |