By Jon Stewart-Taylor
Unaided-eye astronomy is the right place for a beginner to start. Why unaided-eye first? Lots of reasons.
First is that it takes almost no equipment. Just get an introductory book and a planisphere or a good set of star charts, and you're ready to go. This means a very low cost to start. If you do get charts, they can be used when you're ready to move up to binoculars or a telescope.
Second, you can observe at any time, any where. Every clear night is a chance to observe, and you don't have to worry about setting anything up, or losing or damaging expensive equipment.
And, the skills you learn are not only satisfying in and of themselves, but they're an important foundation for observing with binoculars and telescopes. There's an awful lot of space out there, and telescopes have a teeny-tiny field of view: about the size of your finger tip held out at arm's length. You'll need to know aproximately where things are so you can find them.
Lots of things. Here are some, and we'll expand each entry with it's own section, or sometimes with another page in The Recreational Astronomer.
The moon is an ideal object to start on. It's easy to find, and you can see more detail on the moon with your unaided eye than you can see on the other planets with amateur telescopes. You can watch its motion through the sky, and observe its phases. Conjunctions between the moon and bright planets or stars are very beautiful. Eclipses of the moon occur a couple of times a year, and are always worth watching. There are many moon-watching projects in Fred Schaff's Seeing the Solar System. Sketching the moon will train your eye to see more detail. The skills you gain will help you see more observing with binoculars or a telescope.
Any time you are out at night, you have an opportunity to learn the sky better. Even if for just a few moments (while taking out the trash, or walking from the car to the house), you can scan the familiar constellations and fit the stars into their patterns. In five or ten minutes, you can learn new constellations and fit new stars into them, or broaden your knowledge of fainter stars in constellations you already know. To see the faintest stars, you will need a location with no lights, and at least 20 minutes to allow your eyes to fully adapt to the dark.
The more you observe, the more the patterns in the sky will become old friends. They will help you welcome the seasons as they change. The stars become guideposts to the constellations and other celestial objects. As the seasons progress, new areas of the sky will become visible, and you can explore new territory.
Although practice observing is the most important thing, you need to know what you are looking at when you go out. A good sky map is a must. There are different types of maps for different uses, and it is helpful if the maps show the stars as they appear during the different seasons of the year. Although small, the maps in Peterson's Field Guide to the Stars and Planets are good. One of the 6th-magnitude charts such as Bright Star Atlas 2000 or Edmund Mag 6 can be used unaided eye now, and in the future if you want to go on to binocular or telscopic observing.
Each season of the year has its signature stars and constellations, but this is only from the viewpoint of a given time of night. As the night passes, the stars appear to move from east to west. if you stay up and observe long enough, you will eventually see the stars of almost every part of the year. A section of the sky will be drowned out by the light of the sun.
One of the best aids for beginners is a planisphere, or star wheel. These can be set to show the sky at any time of the night, for any season of the year. The only drawback is the relatively small size of the charts.
Some of the best star maps showing constellation "pictures" are in The Stars by H. A. Rey (yes, the Curious George author). They have stick-figure patterns for the traditional constellations, and practically anyone can recognize them as what their names imply. The only drawback to the Rey depictions is that in order to form nice pictures he had to use fairly faint stars, some of which aren't visible under suburban conditions.
Planetarium software can be helpful in learing the sky, but of course it requires a computer, which you may be unwilling or unable to drag along when you're observing, while charts are more portable and don't require a power plug or battery.
No matter which charts you use, you'll still face a basic difficulty: the charts are little dots of ink on paper, while the stars are lights on the dome of the sky. You have to learn to translate the image of the charts to the reality of the sky in your head. This is something which only comes with practice. There are some techniques which can help, though.
It's fun, and it isn't hard. There are two basic approaches to learning to identify the constellations. Some people start by learning the names and locations of the brightest stars, then learn the locations of their fainter neighbors. Other people prefer to learn to recognize patterns in the stars first, and learn the bright stars afterward. Some pople find that making geometric patterns such as triangle sand squares helps them. Others prefer to look for patterns based on the constellation name, such as in the Rey book. Whichever method you feel most comfortable with, paractice is the key to learning.
Asterisms are another aid to identifying stars and constellations. Asterisms are groups of stars in readily recognizable patterns that either sub-parts of constellations, or share member stars from more than one constellation. Some of the more prominent asterisms are:
| Season | Name | Constellation | Description |
|---|---|---|---|
| Spring | Sickle | Leo | The "reverse-question-mark" depicting the mane of Leo |
| Head of Hydra | Hydra | 5 stars marking the head of Hydra. | |
| Summer | Teapot | Sagitarius | stars make quite a good teapot, with the Summer Milky way as steam rising from the spout. |
| Summer Triangle | Cygnus, Lyra, Aquila | Three of the brightest stars in the summer sky. | |
| Northern Cross | Cygnus | 5 stars making up the body and neck of the swan | |
| Keystone | Hercules | 4 stars in a trapezoid. | |
| Fall | "Y" | Aquarius | 4 stars arranged in a "Y" pointing east. |
| Great Square | Pegasus, Andromeda | The four brightest stars in Pegasus and Andromeda. | |
| Winter | Pleiades | Taurus | Also known as the 'seven sisters', in the shoulder of Taurus. |
| Hyades | Taurus | "V"-shaped group: The head of Taurus, with the reddish-orange bright Aldebaran as the eye. | |
| Circumpolar (All year) | "W" | Cassiopeia | May also look like an "M" or an "E" depending on orientation. |
| Head of Draco | Draco | 4 stars in a lop-sided trapezoid |
The number of stars you can see is affected by the amount of light in your immediate surroundings. Under city skies, only a handful of stars may ever be visible. In the darkest skies, you may have trouble finding even well-known constellations among the unfamiliar thousands of stars. Most people will ordinarily have to deal with something in between. Regardless of your conditions, the first stars you will be able to identify individually will usually be the brightest stars. About a dozen are listed below by season (check your star map or planisphere for their locations and the constellations they belong to).
| Winter | Spring | Summer | Autumn |
|---|---|---|---|
| Aldebaran | Capella | Vega | Vega |
| Capella | Castor | Deneb | Deneb |
| Rigel | Pollux | Altair | Fomalhaut |
| Betelgeuse | | Antares | Capella | |
| Sirius | Spica | Fomalhaut | |
| Procyon | Arcturus | ||
| Castor | |||
| Pollux |
Although these are all first magnitude stars, they vary in brightness and color. Hues range from the pure white of Altair and blue-white of Sirius to the yellow of Pollux and the red of Antares. Their seasons, brightness and colors should allow you to learn to recognize them with out too much trouble. Everybody's eyes perceive color differently, and some people have difficulty seeing any color in the stars at all. Most people will be able to distinguish the stars from one another by color, even if they can't agree what color it is.
Two types of objects may be mistaken for bright stars by a beginner. During very short observing sessions, distant airplanes can seem to remain stationary, giving the momentary appearance of a bright star. Or, if you're familiar enough with the constellations to know their customary patterns, an airplane might seem to be a planet.
The planets , while interesting in their own right, can also cause confusion. Of the six planets visible with the unaided eye, four are bright enough to be mistaken for bright stars. Venus is usually unmistakable due to its intense brightness. Jupiter and Saturn are not quite as bright, and have distinctive yellow or amber shades. Mars can vary considerably in brightness, but it's red or orange hues normally make it easy to identify except when it's near one of the red giants such as Aldebaran or Antares.
The planets are also good subjects for unaided-eye observing. you can follow their locations and movement among the stars. Their colors are importatnt clues in identifying them, and also make the very pretty. The book Seeing the Sky has many lunar and planetary obseving projects using just your eyes.
Unaided eye astronomy is the right place to start. It's very low cost and can be done from anywhere without fancy equipment. Learning the sky is important if you plan to start using equipment such as binoculars or a telescope. The moon, the planets, constellations, asterisms, and individual stars are all targets for unaided eye observing. Unaided eye observing is fun, and there's lots of beautiful things to see in the night sky.
© 2006 Jon Stewart-Taylor