Click on the picture to see a video of a stormy day in Tucson!
Astronomy observations will be sparse in Arizona for the next two or three months. While it would be nice to blame it on a lack of government funding for science, it is really due to the weather. Every summer, the Sonoran Desert experiences the monsoon season, marked by almost daily thunderstorms delivering, on average, about half of our annual rainfall. Given that we had almost no rain in our winter rainy season, many Arizonans are hoping for a very strong monsoon this year. We've already seen many thunderstorms, but not too much rain has reached the ground yet.
Because the monsoon is fairly reliable, as it comes every year, most telescopes shut down for the month of August, and many also shut down for the month of July as well. During these shutdowns, a lot of telescope maintenance is done, new computer programs are tested, new observing techniques are tested, and so on.
Often the mirrors are re-coated during this time, too. Over the year, mirrors pick up a lot of dust and grime, which reduces the amount of light making it through the telescope. It takes several days to carefully remove all of grime and the old metallic coating. The mirror is then placed in a giant vacuum chamber, and all the air is pumped out. Evaporated metals are then put in the chamber, and the settle on the mirror to make an even, shiny coating. The mirror is then removed from the chamber and put back on the telescope, giving September's observers a nice, shiny, clean mirror! Some pictures of this process are at the bottom of this page.
Some telescopes do remain open through part or all of the monsoon. Although you don't want to run the telescope during a thunderstorm, after the storms leave and the dome dries, you can open up and work for a couple of hours. I've been told that the air is remarkably clear and steady!