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Weather Related Information for Astrophotographic Sessions
My telescope is mounted on a permanent pier at my home in Pine Mountain Club, Ca. (PMC as the "locals" call it). PMC is just 2 1/2 miles northwest of the parking lot at Mt. Pinos - Southern California's premier observing site for amateur astronomers. On a typical New Moon Weekend in the summer, 50 to 100 amateur astonomers bring their telescopes to Mt. Pinos to observe and photograph the night skies. Because of our proximity to Mt. Pinos, the weather at our home is a very good proxy for the conditions at Mt. Pinos.

As such, I welcome amateur astronomers to use the weather related information on this page to aid in planning their observing and astrophotographic sessions at Mt. Pinos.

View of North slope of Mt. Pinos from Scott and Barbara Rosen's home in Pine Mountain Club, CA
View of North slope of Mt. Pinos
(from Scott and Barbara Rosen's home in Pine Mountain Club, CA)
 
 

Mount Pinos Clear Sky Chart
The Mount Pinos Clear Sky Chart is a valuable tool for predicting the evening's weather conditions. In my experience, the forecast for Cloud Cover and Seeing is quite accurate, and I make many of my photography decisions based upon the information in this chart.

 
 

Current Moon
Knowing the rise and set times as well as the phase of the moon is useful to astronomers since most astronomers observe and photograph faint deep sky objects when there is no moon in the sky (or the moon is a slender crescent). This is because the light from the moon overpowers the faint light from deep sky objects such as galaxies and nebulae.

When the moon is up in the sky, many astrophotographers either photograph the moon, planets, or use narrow band filters (such as Hydrogen Alpha, or Oxygen III filters) to photograph a small section of the visible light spectrum. These types of astrophotography are not hindered by bright light from the moon.

In addition to the Current Moon Phase above, I also use the Sun or Moon Rise/Set Table from USNO at http://aa.usno.navy.mil/data/docs/RS_OneYear.php to calculate when the Sun will set, when twilight is over, and when the moon is not up in the sky.

CURRENT MOON
 
 

Sky Quality Meter Readings
COMING SOON - Pine Mountain Club - Mt. Pinos Sky Quality Meter

The Sky Quality Meter gives measurements of how dark the night sky is at our observing location in Pine Mountain Club. The meter measures the brightness of the sky, and reports it as a "magnitude per square arc second" (also called "mpss"). As such, a reading of 20.0 mpss means that the brightness of the sky is the same as if you took the light from a single star that was magnitude 20.0 and spread it over an area of sky that was a square with dimensions of 1 arc second by 1 arc second.

In astronomy, larger star magnitudes mean that a star is dimmer. As such, the very bright star, Spica, has a magnitude of 1.0 and is easily visible from a large metropolitan city. Conversely, the faintest stars people with good eyes can see from a dark location are about magnitude 6.

So, the ideal dark sky for doing astronomical work will have a large mpss. In fact, the darkest skies have an mpss value of about 22. Typical mpss readings for suburban locations will be about 19, and the center of major cities will have mpss readings around 17.

This chart shows the SQM-LE readings from Scott and Barbara Rosen's SQM-LE in Pine Mountain Club. The meter is pointed just southeast of the zenith (directly overhead), so it is looking right over the top of Mt. Pinos. To see a history of SQM readings, click on the chart for daily, weekly, and monthly graphs.

Sky Quality Meter at the Rosen's House.
Sky Quality Meter Readings
 
 

PMC - Mt. Abel Webcam
Current view looking southwest towards Sawmill Mountain and Mt. Abel from Scott and Barbara Rosen's home in Pine Mountain Club, CA
Current view looking southwest towards Sawmill Mountain and Mt. Abel
(from Scott and Barbara Rosen's home in Pine Mountain Club, CA)