October 5, is “Observe the Moon Night” all over the world. They picked the best possible time to do it: This time of year offers the clearest weather in many places, including our own area, and the Moon’s best lighting happens on Saturday.
Contrary to what’s popularly believed, the Full Moon is not a good target. Sunlight is then shining straight down on its surface, erasing all shadows and making craters and mountains impossible to see. The opposite is true this weekend. Saturday at nightfall, around 7:30 p.m., the First Quarter Moon is nicely up. By chance, it floats right next to the planet Saturn. What a combination!
There’s even a backup plan in case of clouds. Saturn and the Moon will be just as nice one night earlier and for several nights later, though they won’t be next to each other any other evening. If you have any kind of telescope, this weekend is the time to drag it out. As for me, I’d like to share the opening of my new second observatory by inviting former students to come by that night at 7:30 p.m. If you’re free, and you have ever taken my Advanced Class between the years 1976 and 1998 (which was also called the Observing Class), get a quick reservation by writing me at email@example.com. This Moon-and-Saturn exploration with the new Takahashi five-inch refractor is free, no charge, and you can even bring a guest. But space is limited. This is a much smaller building than the old observatory.
If you have your own telescope, the lunar shadowing will be simply ideal from this Friday through next Wednesday, October 9. Here’s a checklist: First look for the prominent mountain chain in the middle of the Moon, right where the shadow line between day and night is running. These are the lunar Apennines, the Moon’s most photogenic mountain range. Watch how those mountains end abruptly at a beautiful crater. This is Eratosthenes.
By Tuesday night, the Moon’s shadow line, called the Terminator, has swept further along to expose the finest crater of them all: the famous Copernicus. Just follow the Apennine mountain chain past Eratosthenes and, bingo! There’s Copernicus, standing all by itself. You’ll smile at seeing its 58-mile-wide crater floor, gorgeous terraced interior walls that rise 11,000 feet high and three mountains right smack in the center. It’s all visible Wednesday and maybe even Tuesday night, even through the cheapest telescope. It can even be observed through steadily braced binoculars.
Remember on Saturday night to point the telescope at Saturn, too. Those stunning rings are still wide open, meaning the opposite of edgewise. Whether they are merely nice or deserving of the adjective “mind-twisting” depends on whether the air is steady. If there’s a little haze that night, so that stars are not twinkling, then the air may remain more or less the same temperature for the first mile or so upward from the surface. This produces steady telescopic images of the Moon and planets.
So, be an observer this weekend. It’s okay to read about the Moon and Saturn, but nothing else comes close to the actual hands-on, eyeballs-on, up-close experience.
Want to know more? To read Bob’s previous columns, click here. Check out Bob’s podcast, Astounding Universe, co-hosted by Pulse of the Planet’s Jim Metzner.