Stargazing

On Friday night I went to the Oak Ridge Observatory for a public viewing. It's an old facility owned by Harvard and the Smithsonian. There are several small brick buildings with roofs that retract. One had a 100 year old 6.5-inch refractor, another a 16-inch cassigrain, another a 25-inch newtonian and in the largest building a 61-inch reflector. Also several amateurs brought their own telescopes and set them up for others to look through.

At the start of evening all were pointing at the moon as it was the only thing bright enough to see at dusk. Then Saturn and Jupiter came out and a few other stars. But before we could look at dimmer things like galaxies, clouds rolled in. Still I saw good details of craters on the moon, the rings of saturn and some of its moons, and Jupiter with two lines of the gas clouds and 4 of its moons. We also spotted a satellite moving across the sky. I learned that satellites in a north-south orbit are probably spy satellites since such an orbit means they'll pass over every point on Earth.

Interestingly enough, someone's $350 8-inch Dobsonian offered as good views as any of the larger ones. The 61-inch probably isn't a fair comparison as it was designed more for film than visual viewings. The focal plane is too wide for the eye so you only see a little of the image at once. It turns out the size of the mirror determines how much light is gathered but for the moon and the planets there's plenty. The larger sizes only help in seeing dimmer things. Any of them can provide enough magnification to see the planets and moon well, and most other things they will just look like points of light anyway. You're not going to see anything like the pretty pictures in books.

Sadly this was the last time there will be public observing at this site as they are shutting it down this summer, moving most of the work to their Arizona facility.