Sidewalk astronomy tonight in Monrovia

It's a clear and slightly chilly night expected in Monrovia. The crescent moon will be out early, and later Jupiter might clear the trees to the east. While tonight's sky is expected to be very transparent (dark), the other atmospheric feature that affects astronomy is scintillation, a measure of how turbulent the air is. Astronomers have a technical term for this: "seeing." The seeing tonight is not expected to be very good, because of different layers of air temperature and upper level winds. That's what gives the slightly watery effect you notice when you view the moon or planets through a telescope, and it gives stars more of a twinkle when you look up at the night sky. Notice the brightest star Sirius tonight due south, and see how it flashes and changes color as its light passes through the turbulent air. It's a little like looking up at the sky from the bottom of a deep swimming pool. But "seeing" is highly variable! If you look for a while, you will have moments when you're looking through air that isn't turbulent, and you can see fine detail: mountain peaks and lava tubes on the moon, cloud belts and swirls on Jupiter. Come take a look if you can. Jane and I have a family engagement tonight so we won't be there, but Todd and Dave and maybe some others are planning to set up from about 6:00 'til 8:00. Best regards, Mojo -- Morris Jones Monrovia, CA http://whiteoaks.com