10 Tips for Moon Watchers Moon’S Brightness Are to Use High Magni- Fication Or to Add an Aperture Mask

Beginning observing You’ll find six labeled maps to help you observe the Moon at www.Astronomy.com/toc.

Two other methods to reduce the 10 tips for Moon watchers Moon’s brightness are to use high magni- fication or to add an aperture mask. Mountain ranges, vast volcanic plains, and more than 1,500 named craters make the High powers restrict the field of view, Moon a target you’ll return to again and again. by Michael E. Bakich thereby reducing light throughput. An aperture mask causes your telescope to act like a much smaller instrument, but The Moon offers something for every amateur astronomer. It’s The terminator will help you at the same focal length. visible somewhere in the sky most nights, its changing face During the two favorable periods described in #3, presents features one night not seen the previous night, and it point your telescope anywhere along the line that Turn on your best vision doesn’t take an expensive setup to enjoy it. To help you get the divides the Moon’s light and dark portions. Astrono- Some years ago, my late observ- most out of viewing the Moon, I’ve developed these 10 simple 4mers call this line the terminator. Before Full Moon, the termi- ing buddy Jeff Medkeff intro- tips. Follow them, and you’ll be on your way to a lifetime of sat- nator marks where sunrise is occurring. After Full Moon, duced me to a better way of isfying lunar observing. sunset happens along the terminator. 7observing the Moon: Turn on a white Here you can catch the tops of mountains protruding just light behind you when you observe high enough to catch the Sun’s light while surrounded by lower between Quarter and Full phases. The Perform a “no optics” survey terrain that remains in shadow. Features along the terminator light should be moderately bright (I sug- The best way to begin your journey as a lunar observer is change in real time, and, during a night’s observing, the differ- gest something in the 60-watt range), but to learn the Moon’s major features. Head out with a sim- ences you’ll see through your telescope are striking. neither your eyes nor the eyepiece ple Moon map, and use just your eyes to identify our only should be in direct view of the fixture. 1natural satellite’s top attributes. The best scope for viewing the Moon The addition of white light suppresses As luck would have it, Stephen James O’Meara’s “Secret Sky” Nearly any telescope will do to observe lunar details. the eyes’ tendency to dark adapt at night. column in the January 2010 issue deals with this very point. He You’ll get great views of the Moon through a 2.4-inch Not dark adapting causes the eye to use gives a detailed description of naked-eye lunar features. Sub- refractor, an 8-inch reflector, or an 11-inch Schmidt- normal daytime vision, which is of much scribers to Astronomy can visit www.Astronomy.com/OMeara 5Cassegrain telescope. Observers with several options (but not a higher quality than dark-adapted night to view this column (and all of O’Meara’s columns) online. permanent observatory) usually pick a scope they can set up vision. In essence, you’ll see more detail many nights in a row. Observing on successive nights makes it because you’re viewing with a better part The Full Moon is for romance easier to follow the terminator’s progress. of your eye. Contrary to what you might think, Full Moon is not the best time to observe our natural satellite, although that’s Cut down the moonlight Work from a list the time when it’s at its brightest. When the Moon is Many observers employ either neutral density filters or One of the best ways to learn the 2full, the Sun lies behind Earth (as we face the Moon) shining variable polarizing filters to reduce the Moon’s light. I Moon is to undertake an observ- directly down on the lunar surface. Shadows are at their mini- prefer the latter because an observer can change how ing project. In the United States, mum lengths, and you can’t see much detail. You can still 6much light the filter transmits. 8the Astronomical League offers one such observe the Moon when it’s full, but the contrast between its project, the Lunar Observing Club. You’ll light and dark sections will be better at other times. learn a lot about our satellite as you work The Moon’s terminator is the line that divides the lit region from the dark part. Because it’s the line through a list of 100 lunar features. marking sunrise (before Full Moon) or sunset (after Full Moon), point your telescope toward it to see When should you observe the Moon? the best shadow details. North is up in this image, so you’ll see it like this with your eyes. Jamie Cooper View the Moon at “prime time” To receive a certificate, you must be a Two intervals during the lunar “month” (from one New During the next year, you’ll get your best views of the Moon by member of the league, either individually selecting dates in the following table. The greatest details will Moon to the next) are best for observers. The first or through an astronomy club. For details about the club, see lie on the sunlit portion of the Moon closest to the terminator. Shoot the Moon begins shortly after New Moon and continues until 2 Point your telescope there for the best views. www.astroleague.org/al/obsclubs/lunar/lunar1.html. How can a celestial object that’s so easy to photo- 3days past First Quarter. Amateur astronomers tend to favor this In Britain, the British Astronomical Association coordinates graph be so difficult to photograph well? The span because the Moon lies in the evening sky. In the evening sky In the morning sky lunar observing. Visit www.baalunarsection.org.uk. Moon is large and bright (only the Sun outshines An equally good observing period starts about 2 days before February 16–24 February 3–12 10it), and you can use any camera connected to any size telescope Last Quarter and goes until the Moon lies so close to the Sun March 17–25 March 5–13 Dig for the details to image it. That’s the easy part. April 16–23 April 4–12 that it’s lost in morning twilight. At these times, shadows are Of the 1,940 named lunar features, 1,545 are craters. But the Moon also contains vast areas of low contrast that May 16–22 May 4–12 longer and features stand out in sharp relief. Another benefit Challenge yourself to see either how small a crater you have little color differential. Recording those regions so they June 14–21 June 2–10 you’ll get when you observe the Last Quarter Moon is that the can detect or how many craterlets in a given area you look like what your eyes see is the hard part. July 13–20 July 2–9 atmosphere before dawn usually appears steadier than it does 9can observe. You’ll need a detailed Moon map for this project. Luckily, we live in the digital age. Unlike when astrophotog- August 12–18 August 30–September 6 after sunset. After sunset, a lot of heat remains in the atmo- September 10–17 September 29–October 5 For the second challenge, you can choose a lunar sea, but raphers used film, it costs nothing extra to take 200 images sphere. As hot air rises and cooler air falls, the resulting turbu- October 9–16 October 28–November 4 usually a large, flat-bottomed crater works best. For example, if instead of just one. Examine them, throw away what you don’t lence leads to unstable air — what observers call bad seeing. November 8–15 November 26–December 3 you search the large crater Plato, you’ll find four craterlets on its like, change one or more parameters (including the techniques December 7–15 December 26–January 2, 2011 floor, each about 1.2 miles (2 kilometers) across. Lunar observ- you used to process the images) each time, and shoot some Michael E. Bakich is a senior editor of Astronomy. ers consider seeing these craters a test for a 6-inch telescope. more as you continue to perfect your techniques.