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| Site selection was made with the following considerations in mind: | ||
| CONSIDERATION | SIERRA REMOTE INFORMATION | REMARKS |
| Location | N 37.07 W 119.4 degrees |
Located in the center of California's Sierra Nevada Mountains. Go here to see some maps. |
| Elevation | 4,610 feet |
Obviously the higher the altitude the better but going too high would introduce problems of accessibility in the winter due to snow loads and public road plowing issues. |
| Thermal Considerations of Surrounding Material | low lying vegetation |
The thermal impact of low lying vegetation surrounding the observatories is very low. Go here to see an image of what the surrounding vegetation looks like. |
| Airflow Over the Site | Laminar above 300 feet unless the wind is out of the East |
The site is on top of Bald Mountain that rises several thousand feet above it's surrounding terrain in all directions. The prevailing Westerly wind moves smoothly over the site. There are no mountains West of the site that would cause atmospheric turbulence. This allows the airflow to be laminar over the site and allows for the best possible seeing conditions at the 4,610 foot altitude. |
|
Number of Photometric nights each year |
Around 275 |
California's central valley has one of the highest "ratings" for clear days (and thus photometric nights) of anywhere in the Western United States. |
|
Thunderstorm activity |
Unusually low |
California's central valley has one of the lowest incidents of "Thunderstorm activity" of anywhere in the country. |
Thermal Inversion Layer |
Above the local inversion layer |
The thermal inversion layer poses a problem for imaging from within California's central valley. Go here to see what it looks like. The site is at a high enough altitude that when this layer forms over the valley, the site is above the layer. |
Tree Elevation & Wind Consideration |
Very protected, the average maximum gust <10 mph. Relatively low tree line |
The site is surrounded by Ponderosa Pine trees. This offers good protection from strong wind gusts with tree elevations of only 5 degrees to the North, 10 degrees to the South, 15+ degrees to the East and 20+ degrees to the West. |
Seeing Conditions |
FWHM of only 1.0 - 1.5 arcsecond |
The SBIG seeing monitor shows the seeing to hover between 1.0 and 1.5 arcsecond for the majority of the time. There are conditions when the seeing goes sub-arcsecond. Click here for an example. |
| Sky Brightness | Measured at 21.78 magnitudes / sq arcsecond, V band |
No streetlights are visible. The sky gets brighter toward the SW, low to the horizon, due to the top of the light dome from the city of Fresno, California. |
Light Pollution |
Bortle scale = 3 |
The Bortle scale is a measure of light pollution. It would be difficult to get a lower index and still have services like power, a T-1 line and Winter accessibility in the Sierra Nevada Mountains. Go here for a light pollution map. |
Full T-1 internet connection |
A dedicated T-1 land line is available at the site. |
To run a remote observatory efficiently, a fast and reliable high-speed internet connection is essential. We are getting between 10-11 MB/min out of our T-1 line. A T-1 land line is usually not available in remote parts of the Sierra Nevada Mountains. |
AC Power |
Power is available at the site. |
So many sites under earlier consideration would have been wonderful, but did not have any access to power. Being able to connect to the grid is essential. |
Accessibility |
All year |
Accessibility in the Winter is essential. Having access to the site to service hardware all year round is a very important consideration. The site is accessible by a two-wheel drive vehicle in the winter. |
Security |
High |
The site is not visible from any road. The site is behind a locked gate and is not accessible by the public. The site is surrounded by private property. |
www.sierraremoteobservatories.com