Night Sky Quality Monitoring Report
Yosemite NP, California
Sentinel Dome, September 7, 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 | YOSE |
 Narrative: Very clear, steady, excellent night for Astronomy. Light domes brighter from valley cities than on 8/31/2005, presumably because of clearer air. Gegenschein not visible. Some smoke below summit, should not interfere. No clouds. Sky near zenith very dark, excellent detail in Milky Way, to south and west significantly degraded.
|
| Site Name | Sentinel Dome | |
| Longitude | -119.58426 | |
| Latitude | 37.72316 | |
| Elevation (m) | 2478 | |
| Date (UT) | September 7, 2005 | |
| Time Start (UT) | 3:59:09 | |
| Data Quality | Excellent | |
| Equipment | SBIG, Nikon 50mm f/2, 6084 | |
| Observers | D.Duriscoe, C. Duriscoe | |
| Air Temp (°F) | 55 | |
| Rel Humid (%) | 43 | |
| Wind Sp (mph) | 5 | |
| CCD Temp (°C) | -20 | |
| Exp (seconds) | 15 | |
| Bortle Class | 4 | |
| ZLM | 6.6 |
| 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 |
3:59:09 4:20:03 |
0.133 |
0.036 |
21.89 21.76 |
-7.35 |
-6.51 |
18.84 |
22.10 |
PAN HEMI |
| 2-Start End |
4:59:14 5:20:06 |
0.133 |
0.038 |
21.39 21.12 |
-7.36 |
-6.57 |
18.88 |
21.96 |
PAN HEMI |
| 3-Start End |
5:59:17 6:20:07 |
0.128 |
0.040 |
21.48 21.53 |
-7.37 |
-6.59 |
19.01 |
21.87 |
PAN HEMI |
| 4-Start End |
6:59:19 7:20:13 |
0.125 |
0.045 |
21.61 21.62 |
-7.39 |
-6.64 |
19.00 |
21.84 |
PAN HEMI |
| City | Distance (km) |
Azimuth | 1st Data Set Brightness (mags) |
Image |
|---|---|---|---|---|
| Fresno | 106 | 190.1 | 4.39 |
 |
| Merced | 93 | 239.5 | -2.88 | |
| Modesto | 125 | 267.2 | -4.34 | |
| Stockton | 154 | 280.8 | ||
| Sacramento | 190 | 300.1 | -3.21 | |
| Reno | 203 | 354.2 | 0.48 | |
| Total | -5.42 |