Sites for good seeing in S. California?
Posted 04 December 2012 - 06:59 PM
Are there some favorite locations for good seeing in S. California? With the usual safety and permission issues not too serious?
Posted 05 December 2012 - 04:39 PM
--on the upslope side of mountains where the prevailing wind comes from that side.
--in the center of wide valleys, especially mountain valleys
--a couple days AFTER a front has passed and the air is becoming stagnant and non-moving.
--when the jet stream is NOT overhead, but several hundred miles to the north or south
--when the temperature differential between 9pm and 3am is small. This can happen in the desert or mountains, but is more common in the mountains.
Finding a site with good seeing much of the time is uncommon. That's why the Mt. Wilson area is so revered.
But, alas, it is no longer dark there, so deep sky viewing is seriously compromised.
I find the Desert Center, Amboy Crater, and area in between to be the darkest areas in SoCal (21.6-21.9 SQM average), but they rarely have excellent seeing.
In contrast, Mt. Pinos, Lockwood Valley, and the Taft area up to Figueroa Peak above Santa Barbara are dark enough (21.2-21.5 average) but usually have better seeing. This year, Mt. Pinos has come through with several nights of seeing well better than 1", but the stagnant air did result in a slight diminution of transparency on those nights.
We are so used to searching for dark sites in SoCal that seeing conditions usually aren't considered. Put it this way: excellent darkness, high transparency, and excellent seeing are rare in the world, and in SoCal, it's rare enough that I think once every 5 years is about normal, and not for an entire night, either.
Posted 05 December 2012 - 05:03 PM
when the jet stream is NOT overhead, but several hundred miles to the north or south
A lot of people do not factor in the jet stream. You can go out, check the skies, and think it will be a good night for viewing. Then, you find that the images are blurred out, especially on the planets. One of the reasons for this is often the jet stream. I check a half dozen weather sites each day, and one of them shows the location of the jet stream. When the jet stream is overhead, I still view, but don't expect good, detailed views of the planet's surface.
Posted 06 December 2012 - 12:00 AM