Monday, March 13, 2006
Observing the Moon for beginners
Beginning backyard-astronomers often ask me “what do I need to start observing the Moon”. Basically you only need two things to start off with lunar observing: a small telescope (or binoculars) and a map of the Moon. You also should know a few other things: when to observe the Moon and what to observe (as a beginner). In this article I will try to answer these questions. In the near future I will write an article for those wo are past the beginning stage, the "intermediate" observer. This article however, is meant for the beginning lunar observer.
You can use any telescope with good optical quality to observe the Moon. A 70mm or 80mm refractor or a 4-inch reflector will be just fine for starters. When you already own a pair of binoculars, use them! There is no need to rush to the nearest astro-store and buy a telescope right away.
I will not discuss (the quality of) telescopes and binoculars in this article. There are many good other resources on the web and in astronomy magazines that can help you on deciding which telescope or binoculars to buy. You can find some useful links in my beginner's pages and equipment links on my old website, backyard-astro.com. The best advice I can give you before buying any astronomy related equipment: take your time, go to a local astronomy club or visit a star party and look through different instruments yourself, before you decide what to buy. In the end, this will save you a lot of disappointment and money.
Map of the Moon
You need a map of the Moon because you will be visiting a place that (until now) is unknown to you. You need a "roadmap" to find your way around. There are many lunar maps available from bookstores and from Internet stores like Amazon and Sky Publishing, but for outdoor use my favourite is the “Field Map of the Moon” from Sky and Telescope. This map is laminated, so it can be used outdoors under all weather conditions. You will find about 1,000 features labelled (and indexed) on the map. The map is made by Antonin Rukl, who (IMHO) is the best lunar cartographer around right now. You can get this map in two versions, the "normal" naked eye view version, and a mirror-reversed version. Before ordering, check which one you need for using with your particular binocular or telescope. This depends on the type of instrument you are using for observing the Moon. Just have a look at the three images below (click to enlarge).
Compare the views of the Moon through your telescope/binocular with these images. If you see the Moon as shown in the first two images, you will need the standard map (for naked-eye-views, binoculars and reflectors). If you see the Moon as shown in the third image, you will need the mirror-reversed map (for telescopes that work with a star-diagonal, like refractors, maksutovs and cassegrains). If you’re not 100% sure which one you need, just contact Sky and Telescope before ordering.
A lunar map will help you to identify the different lunar features, so it is one of the basic things you need when you start observing the Moon. When comparing your telescopic views of the Moon with a lunar map for the first time, you’ll probably wonder where to find east, west, north and south. The image below should help you finding your way around. I highlighted four key-features that should help you to get the directions right: Mare Imbrium (north), Mare Crisium (east), Tycho (south) and Mare Humorum (west).
When is a good time to observe the Moon?
The answer to this question is very simple. Whenever the sky is clear and the Moon is visible. The Moon always has some interesting features to observe, even the full Moon. The bright lunar rays for example, are at their best when the Moon is full. A full Moon is also very useful to train your lunar orientation and find your way around as a beginner. Try to identify all the dark area’s, the Maria or seas, when the Moon is full.
What can you observe as a beginner?
When observing the moon through a telescope or binoculars for the first time, you will probably notice two things: there are large bright and dark areas on the lunar surface and the views along the line that separates the dark and light hemispheres of the Moon are the most spectacular.
1. Dark and light areas on the Moon, the Maria and Terrae
Roughly, the lunar landscape can be divided in two types of surface, the dark areas or Maria and the light areas or Terrae. The Maria, or seas, are the grey smooth plains on the lunar surface. The Terrae, better known as highlands or uplands, are the bright and rugged areas of the Moon, full with craters, mountain-ridges and other interesting features. The image below, should give you an idea about the dark seas and bright highlands. It is heavily processed to bring out the contrast between the two types of terrain. Anyway, trying to identify the different dark and light areas is a very good starting point for a beginning lunar observer.
Dark and light areas, Maria and Highlands
2. Highly detailed lunar features along the terminator
You will be amazed by the amount of detail you can observe along the terminator, the line that separates the light from the dark hemispheres of the Moon. When you observe the moon on a few consecutive nights you will notice that the terminator creeps over the lunar surface from east to west, changing the views not only from day to day, but also from hour to hour. You can see craters, mountains, rilles, domes, wrinkled ridges and more. I shot the image below on the 28th of March 2004. It shows part of the terminator of a 7-day-old Moon. As you can see, the amount of detail is simply overwhelming.
The lunar terminator
You can try to identify some of the larger craters for starters. If you need some kind of guideline or list of features to observe, follow this link to the Lunar Club of the Astronomical League. They have an observing list of lunar features, which will keep you busy for a while.
So if you want to observe the Moon, get a map, a pair of binoculars or a small telescope, and start with simply enjoying the views you get from this wonderful object. Try to identify the different mare and highland areas, and if you’re up to it, maybe some craters or other interesting features along the terminator. Maybe you get hooked and want to learn more about the Moon, start imaging the Moon, get into lunar geology, or just simply enjoy the views. No matter what you do, keep in mind that the single most important thing about amateur astronomy (and in fact every hobby) is that you are having fun and enjoy what you are doing.