Stargazing by wk98255

Hobbies & Leisure

Stargazing

published by Barnes & Noble

Know what’s out there. Like a great work of art, the night sky is even more fascinating if you’re able to appreciate the features within it. So step outside and demystify the universe—one tiny speck of light at a time—with this all-encompassing guide to: • Basic tools and techniques you’ll need for effective stargazing • Stars, planets, and galaxies you can see through binoculars or a telescope • Special astronomical events—meteor showers, eclipses, comets, and more

What Is Stargazing? Stargazing means a whole range of things: simply watching the night sky, identifying celestial objects (such as stars, planets, and distant galaxies), understanding and predicting their motions, and appreciating their beauty. Some people stargaze out of interest in the science of astronomy, some seek the challenge of locating faint and distant objects, and others enjoy sensing the vastness of space and their own place in the universe. All you have to do to stargaze is step outside, look up at the night sky, and start asking questions: Where do the stars rise and set? What constellations can I see? Are all stars white, or do they have different colors? How can I tell a star from a planet? The more you learn and practice, the more rewarding your experience will be.

How to Get Oriented in the Night Sky You don’t need to be on a remote mountaintop with a fancy telescope to enjoy stargazing. These five steps will help you get started anywhere with just your naked eye:

1. Know Where You Are What you can see in the night sky depends on where you are on Earth. If you’re in Seattle, for example, you can see the Big Dipper circle slowly above you in the sky at any time of the night, at any time of the year. In Miami, however, the Big Dipper rises in the northeast and sets in the northwest during the summer, and can’t be seen at all in the winter. This is because latitude—how far north or south you are—affects what stars you see. (On the other hand, longitude—how far east or west you are—does not.) You can find your latitude on a map or look it up online. It’s also important to know which way is north so you can get your bearings in the sky. If you’re not sure what direction you’re facing, look at a compass or remember that the Sun will have set in the west. With practice, you’ll be able to find north just by looking at the stars.

2. Look Up When you go outside, always wait a minute for your eyes to adapt to the dark before you get started—this will help you see fainter stars. Look at the ground for a few minutes until you feel adjusted, and avoid looking at streetlights or headlights or using flashlights while you stargaze.

• Zenith and nadir: In stargazing terms, the highest point in the sky directly above you is called the zenith, and the point directly below you (under your feet) is called the nadir. It’s important to note that, unless you’re standing at exactly the North or South Pole, the sky does not rotate precisely around the zenith. • Stars vs. planets: At first, the night sky may look vast and intimidating, with what seems like an infinite number of stars. The human eye, however, can see only about 6,000 stars, even in the best observing conditions. The first objects you’ll see are the brightest ones—and these are often planets, not stars. A good way to tell planets from stars is with the “twinkle test”: stars twinkle, whereas planets appear to shine steadily.

The Big Dipper and Little Dipper The Big Dipper is one of the brightest and easiest asterisms, or clusters of stars, to spot in the night sky. (It’s not technically a constellation, as it makes up only part of the full constellation Ursa Major.) Four stars make up the Big Dipper’s “bowl,” and another three make up its “handle.” The two stars at the end of the Big Dipper’s bowl are pointers—if you join these with an imaginary line and extend that line from the bottom of the bowl upward, you find the North Star. Or, if you can spot the less bright Little Dipper, which has the same shape as the Big Dipper but is upside-down, you can also find the North Star at the end of its handle. Big Dipper

3. Find the North Star The North Star, or Polaris, is a good first star to identify— it’s the only star that’s always in the same spot in the sky, no matter what time of night or time of year. There are two ways to find it:

Polaris Mizar

The Hand Scale The North Star is always straight above the north horizon, and its height in the sky is the same as your latitude. For example, in Phoenix (latitude 33°N), the North Star is 33° above the horizon looking due north.

1°

30°

Alcor

Little Dipper

4. Know How the Sky Moves The motion of the night sky is caused by the Earth rotating west to east on its axis, an imaginary line between the north and south poles. The Sun, Moon, stars, and planets all seem to rise in the east and set in the west due to this rotation.

The Celestial Sphere

20°

north celestial pole

zenith

10°

If you hold your arm out straight, you can use your hand as an approximate scale to measure degrees in the sky: a clenched fist is 10°, and the width of an index finger is 1°. Start with the bottom of one fist lined up with the north horizon then stack your other fist on top, then move your bottom fist on top of that one, counting 10° with each fist. In Phoenix, for example, if you stack three fists and count 30°, then stack three index fingers to reach 33°, the North Star should be right above your top finger.

cel est ial

horizon equ ator

To help visualize these motions in the sky, stargazers imagine the Earth at the center of a giant spinning celestial sphere that’s covered with all the stars. If you extend the Earth’s axis from the north pole until it hits the celestial

Stargazing

www.quamut.com sphere, you find the north celestial pole. All stars rotate counterclockwise around this point, which, conveniently, is also the location of the North Star. Only stars that lie on the celestial equator will rise/set exactly in the east/west. Stars that lie between the North Star and the horizon will stay above the horizon all night long.

Diurnal and Annual Motion Because of the Earth’s rotation, all stars rotate around the north celestial pole once each day. This is called diurnal motion. The Earth also moves in its orbit around the Sun— finishing a complete cycle in one year—which causes the stars to rise and set an average of about four minutes earlier each night. Called annual motion, this adds up to about a half hour each week, or two hours each month. Annual motion is what allows us to see different stars at different times of the year. Note that planets, though, don’t follow the same motions of the celestial sphere. Instead, they follow a different path called the ecliptic (see The Planets).

5. Locate Prominent Constellations Once you’ve found the North Star, find a prominent constellation to use as a landmark. You’ll then be ready to find more objects using a star chart (see Stargazing Tools) and move on to more advanced stargazing. Different prominent constellations are visible at different times of the year.

Prominent Summer Constellations/Asterisms • Summer Triangle: Lyra This large triangle Aquila Vega is made of three of the brightest stars Altair in the sky: Vega, in Saggitta the constellation Lyra Deneb Cygnus (the Lyre); Deneb, in the constellation Cygnus (the Swan); and Altair, in the constellation Aquila (the Eagle). To find the Summer Triangle, look high overhead on most summer nights. If it’s dark enough to see the bright belt of the Milky Way, that belt will cut straight through the Summer Triangle.

Weather When it’s cloudy, rainy, or snowy, it’s best to save stargazing for another night. Sometimes you can observe the Moon or bright planets through a very thin cloud cover, but if there’s a chance of any precipitation, you shouldn’t use telescopes or expensive binoculars. The online Clear Sky Clock (www.cleardarksky.com/csk) can help you predict how observing conditions may change over the course of a night.

Prominent Spring Constellations/Asterisms • Ursa Major (Big Dipper): “Ursa Major” is Latin for “big bear.” The Big Dipper comprises just part of the bear— the back of its body and its tail. To find Ursa Major, see “3. Find the North Star” earlier in this section. • Ursa Minor (Little Dipper): “Ursa Minor” is Latin for “little bear.” The Little Dipper and Ursa Minor are the same thing—the North Star is located at the end of the bear’s tail. To find Ursa Minor, see “3. Find the North Star,” earlier in this section. • Leo: Leo is a lion with his mane defined by bright stars that look like a backward question mark. Leo is directly below the bowl of the Big Dipper. To find Leo, draw an imaginary line south (away from the North Star) through the two stars that make the left edge of the bowl, and you’ll hit Regulus, a star on Leo’s chest.

Urban Areas and Light Pollution Stargazing in cities can be difficult because light pollution from streetlights, buildings, and cars creates a glow that blocks the night sky. To cut down on light pollution outside your home, close all your drapes and blinds, and turn off any exterior lighting. If you live in a densely populated area, your best bet is to find a city park or to drive to a more rural area for darker skies. Even if you can’t get away from light pollution, though, you should still be able to see the brightest stars, and the major constellations will be easier to pick out.

Stargazing Tools A variety of tools can enhance your stargazing by helping you locate objects in the sky and see them in more detail.

Star Charts Star charts are road maps for the sky: they show the locations of stars, galaxies, nebulae, and clusters, as well as directions (north, south, east, west) and degrees to help you find them. A good starting point is a planisphere, a circular map that lets you adjust the view depending on the season. There are different planispheres for different latitudes, so make sure to get one that matches your location.

When and Where to Stargaze Your stargazing experience will be much better if you have good observing conditions.

Full Moon vs. New Moon

Prominent Autumn Constellations/Asterisms • Pegasus: This mythical winged horse includes four bright stars, the Great Square of Pegasus, that outlines its body. To find Pegasus, first find the star in the bowl of the Big Dipper that’s closest to the handle. Now draw an imaginary line from this star through Polaris, and you’ll hit a corner of the Great Square. • Cassiopeia: This mythical queen sitting on her throne is marked by a pattern of five bright stars that look like a big “W.” To find Cassiopeia, follow the first star in the handle of the Big Dipper through Polaris.

Prominent Winter Constellations/Asterisms • Orion: The mythical hunter, Orion, is outlined by a rectangle of bright stars with three bright stars in the middle representing his belt. Betelgeuse, the star at his left shoulder, has an orange-red color. Far to the lower left of his belt is Sirius, the brightest star in the sky. To find Orion, look south for three bright stars in a short, straight line—Orion’s belt. The two bright stars above the belt are Orion’s shoulders; the stars below the belt are his knees and feet.

Pegasus Cassiopeia M31 Segin Perseus Algol

The Full Moon is very bright and tends to wash out a good portion of the sky. Though it’s fun to observe the Moon and easy to observe planets and bright stars while the Moon is up, the best time to observe faint objects in the sky is during the New Moon, when the Moon is not visible at all. The Moon progresses from Full Moon to New Moon and back over a 29.5-day cycle (see The Moon), and you can find the monthly New Moon dates on most calendars.

How to Use a Star Chart

Atmosphere and Temperature

Star charts never look exactly like the night sky and can be confusing at first. To get used to using them, try these tips:

The atmosphere has a big effect on how clear the stars and other objects appear. At sea level, the air is relatively thick, and turbulence causes stars to blur and twinkle (an effect that astronomers call seeing). At higher altitudes and in drier locations, though, the thin air and low water vapor make for much better observing conditions (which is why most big observatories are built on mountaintops). Cold air also improves visibility because it’s stiller than warm air.

• Remember that star charts are meant to be held upside down, so unlike regular maps, west will be on the right, and east will be on the left. • Hold the chart so that north on the chart faces the north horizon (see How to Get Oriented in the Night Sky). • Bigger dots on a star chart represent the stars that are brightest (and easiest to spot), so try finding these first.

The information contained in this and every Quamut guide is intended only for the general interest of its readers and should not be used as a basis for making medical, investment, legal or other important decisions. Though Quamut makes efforts to create accurate guides, editorial and research mistakes can occur. Quamut cannot, therefore, guarantee the accuracy of its guides. We disclaim all warranties, including warranties of merchantability or fitness for a particular purpose, and must advise you to use our guides at your own risk. Quamut and its employees are not liable for loss of any nature resulting from the use of or reliance upon our charts and the information found therein.

Photo Credits: Page 1: Ian McKinnell/Alamy; Page 2: Scott B. Rosen/Bill Smith Studio; Page 3: 7x50 ED Astronomical Binoculars/Courtesy of William Optics/http://www.williamoptics.com (photo 1), Courtesy of Celestron (photos 2-4), Page 4: NASA, ESA and AURA/Caltech (photo 1), Stocktrek Images/Getty Images (photo 2), Courtesy of USGS (photo 3), © CalculatorCat.com (photos 4-11); Page 5: MPI/Hulton Archive/Getty Images (photo 1), Corbis (photos 2 and 8), NSSDC and NASA (photos 3-6), NASA/JPL-Caltech (photo 7), Space Frontiers/Hulton Archive/Getty Images (photo 9), Kanwarjit Singh Boparai/Shutterstock (photo 10); Page 6: Roger Ressmeyer/Corbis (photo 1), Courtesy of SOHO (ESA & NASA) (photo 2), Norbert Rosing/National Geographic/ Getty Images (photo 3), NASA/JPL-Caltech/STScI (photo 4). Illustrations by Precision Graphics.

Stargazing

www.quamut.com • Don’t use a regular flashlight to view your star chart, because that will make it hard for your eyes to readjust to the dark. Cover your flashlight with a red filter (such as red cellophane) or use a dim flashlight specifically designed for stargazing purposes. • Note that objects not on the celestial sphere—planets, comets, asteroids, and satellites—don’t always appear on star charts. (To find them, see “Planet-Finding Charts” and “Ephemerides,” later in this section.) • Don’t expect every star on your chart to be visible if you’re observing an urban sky (or if it’s near Full Moon), and don’t expect every star in the sky to be on your chart if you’re observing a very dark sky.

• 7×50: magnifies 7 times and has a 50mm aperture (front lens size) • 8×35: magnifies 8 times and has a 35mm aperture

Magnitude

Telescopes

Star charts indicate how bright objects in the sky are, using a magnitude system. The lower an object’s magnitude, the brighter the object is, and the easier it is to find. A decrease of 5 magnitudes means a 100x increase in brightness. Most stars and galaxies have positive magnitudes, whereas brighter objects such as planets and the Moon have negative magnitudes. The following chart lists a few objects of various magnitudes, from brightest to dimmest.

Telescopes are essentially buckets for collecting light— the bigger the telescope, the more light it will collect, and the better you’ll be able to see faint, distant objects. Telescopes can be pricey, though, so before you buy one, put careful thought into which type is best for you. There are three main categories of telescopes: refractors, reflectors, and catadioptrics.

Magnitude

Example

–27

Sun

–12

Full Moon

–5

Venus (the brightest planet)

–1

Sirius (the brightest star)

Vega (a prominent star in the Summer Triangle, around which the magnitude system is based)

3.5

Limit of what you can see with the naked eye in urban locations

6.5

Limit of what you can see with the naked eye in dark locations

Limit of what you can see with binoculars in dark locations

Limit of what the world’s largest telescopes have observed

The 8×35 magnifies more powerfully but collects less light than the 7×50, so the 8×35 is not as good for observing very faint objects. High-end binoculars (so-called supergiant binoculars) range up to 20×100 or above and look more like twin telescopes than standard binoculars. Your hands will shake when holding any type of binoculars, making fainter objects difficult to see. It’s best to prop your binoculars up on something steady, or get a binocular holder or a tripod.

Telescope Type Advantages Refractor (uses lenses only)

Planets don’t move with rest of the sky but instead follow the path of an invisible line called the ecliptic. As a result, you can’t depend on landmarks such as the North Star or constellations to locate them. In a given evening, a planet might be visible for all of the night or part of the night, or it might not be visible at all. Each planet is visible within a fixed schedule that may not change much over a few days but will be drastically different after a few weeks. Planet-finding charts, found in astronomy magazines or online (see Stargazing Resources), give you a rough idea of where to find planets at different times of year. They usually will point you to the constellation nearest to the planet.

Ephemerides Ephemerides (singular ephemeris) are tools professional astronomers use to locate the exact positions of planets, asteroids, comets, the Moon, and other satellites. They are tables or data files containing the celestial coordinates of an object at regular intervals throughout the night. You can generate ephemerides easily online (see Stargazing Resources).

Binoculars Binoculars are an inexpensive, lightweight alternative to telescopes. With a good pair, you can spot objects as faint as magnitude 10. The most popular types of binoculars used for stargazing are:

Disadvantages • Not good for deep-space objects • Can show chromatic aberration (colored fringes around bright objects) • Expensive • Can be very long • Can be heavy • Can have distortion (coma) near the edges of the field of view • Mirrors can become mis aligned and require adjustment

Reflector (uses mirrors only)

• Relatively inexpensive • Good for beginners • Stable • Yields high image quality • Good for faint objects

Catadioptric (uses lenses and mirrors)

• Can be • Compact expensive • Portable • Shows a slight • Great for loss of contrast photography • Good compro- • Can require a number of mise between accessories a refractor and reflector

Most planispheres show only objects that are brighter than magnitude 4.5, whereas larger star charts show objects brighter than magnitude 6 or so.

Planet-Finding Charts

• Durable • Easy to set up • Yields pristine image quality • Good for viewing the Moon and planets

Telescope Accessories There are countless telescope accessories you can buy to aid your stargazing ventures. Some are absolutely necessary, and others are essential only for professionals. • Mount: An essential accessory, a mount holds the telescope steady and lets you aim it at different points in the sky. There are two types of mounts: azimuth, which allows you to move the telescope up and down and in lines parallel to the horizon, and equatorial, which is aligned with the celestial poles. Azimuth mounts are best for beginners. • Eyepiece: An eyepiece, which determines your field of view, is also essential for telescope stargazing. Most telescopes come with an eyepiece, but rarely a good one. Eyepieces are categorized by focal length (in mm) and barrel size (1.25" is standard). Larger focal lengths mean wider fields of view, and larger barrel sizes make better eyepieces.

• Filter: Though not absolutely essential, a filter reduces glare, increases contrast, protects your eyes, and increases the definition of what you see through the telescope. The most popular filters are lunar filters, planetary filters, and solar filters. You should never observe the Sun without using a proper solar filter. • Drive system: A drive system makes the telescope track the sky and keeps objects from drifting out of your field of view. It isn’t essential, but you’ll need one if you plan to use your telescope for astrophotography. This requires you to align the telescope to the Earth’s polar axis, however, which can be time-consuming. • Computer-driven mount: This type of mount allows you to tell the telescope what you want to observe, and the computer then finds it for you. Many expensive telescopes come with a computer-driven mount, which makes it quick and easy to find faint objects in the sky and may even let you control the telescope from a laptop. The flip side, though, is that a computerdriven mount takes some of the fun and challenge out of stargazing. • Dew shield: An optional accessory, a dew shield is a long tube that slips over the front of the telescope to slow the condensation of harmful moisture (dew) on the telescope, which often happens on damp nights. • Barlow lens: A Barlow lens is another optional accessory that connects to the eyepiece and can bump up magnification by 2x or more. It’s important that the Barlow lens be the same barrel size as your telescope’s eyepiece. Also note that any objects you view become dimmer the more they’re magnified.

Tips for Using Telescopes Telescopes can be tricky to use, and it takes a lot of practice to become completely comfortable with them. You’ll be at an advantage, though, if you remember a few tips: • Know that refractor and catadioptric telescopes make objects appear upside-down. Most objects you’ll be viewing will be roughly symmetrical, so this won’t seem obvious at first. It might disorient you, though, when you start to move the telescope, and it can make using a Moon map a bit confusing. • Know that reflector telescopes make objects look backward. This can also be disorienting, especially after you’ve been looking through other types of telescopes. • Practice star hopping. Point your telescope on a star you recognize, and with the help of a star chart, identify a trail of stars that lead to the faint object. You can then “hop” from star to star along this trail with your telescope—the smaller the hops, the better—and end up at the object you were searching for. • Don’t forget that the Earth is constantly rotating— which means that objects in the sky appear to move (see How to Get Oriented in the Night Sky) and will drift out of your telescope’s field of view, often faster than you’d expect. If you don’t have a drive system, you’ll need to nudge your telescope every few minutes to follow an object. • Use averted vision: when trying to view very faint objects, look a bit to the side of where the object is, and you’ll actually see it better. The edges of your retina are better at detecting faint objects than the center, which is more sensitive to color than to brightness. • Never use a dirty cloth to clean your telescope. Telescope lenses and mirrors can easily be scratched or damaged, so use chamois leather or a clean, soft cotton handkerchief. And be careful with glass-cleaning cloths—some types of cloths can actually rub off the special coatings from telescope mirrors. • If you wear eyeglasses, take them off. You’ll see better if you put your eye right up to the eyepiece, and you can simply adjust the telescope’s focus knob to compensate for your vision.

Stargazing

www.quamut.com Stars, Nebulae, and Galaxies The objects you can see in the sky with your naked eye are mostly stars and sometimes planets, but with binoculars or a telescope, many other types of objects become visible. That being said, if you just have a small, basic telescope, don’t expect to see a lot of spectacular detail and colors— most of the published photographs of beautiful, multi colored deep-sky objects were taken with the Hubble Space Telescope or by professional observatories.

Stars Stars are large balls of burning gases, like our Sun, for example. They can have different colors depending on their temperature (hotter stars are whitish-blue, cooler stars are red, and intermediate stars can be orange or yellow). • What you need to see them: The brightest stars can be seen with the naked eye even in urban areas. • Examples to look for: If you look carefully, you can see the color variations between different stars. For example, Betelgeuse (the left shoulder of Orion) looks orange-red, whereas Rigel (the left foot of Orion) is much hotter and looks blue.

Double Stars Double stars are pairs of stars that appear to be very close together. Sometimes this is an illusion, and one star is actually hundreds of light-years behind the other. Other times they are binary stars that orbit around each other. • What you need to see them: Some double stars can be distinguished with the naked eye, but most look like a single star until you use binoculars or a telescope. • Examples to look for: The middle star of the Big Dipper’s handle is actually a double star: Mizar and Alcor can be distinguished without a telescope on a very clear night. With a small telescope, you’ll see that Rigel in Orion is also a double star.

Open Clusters Open clusters are loose aggregations of stars that look like several individual stars in close proximity. • What you need to see them: You don’t need any tools to see many open clusters, but you can see more of their stars with binoculars. • Examples to look for: The Pleiades (the Seven Sisters), shown above, are an open cluster with at least six stars visible to the naked eye.

Globular Clusters Globular clusters are aggregations of hundreds of thousands of stars so tightly concentrated that they look like a continuous patch of light. • What you need to see them: You’ll need binoculars or a small telescope to get a good look. • Examples to look for: M13, in the constellation Hercules, is the best-known globular cluster.

Planetary Nebulae Planetary nebulae are glowing regions of gas that have been ejected from a dying star. They look like faint, irregul arly shaped, fuzzy smudges, some of which are ring-shaped. • What you need to see them: You’ll need a small telescope to view most nebulae. The bigger the telescope, the more detail you’ll be able to see. • Examples to look for: The Ring Nebula in the con stellation Lyra is probably the best known planetary nebula. You can spot it most easily in the summer.

Diffuse Nebulae Diffuse nebulae are large regions of gas where new stars are in the process of forming. Like planetary nebulae, they look like fuzzy splotches. • What you need to see them: Use a small telescope. • Examples to look for: The Orion Nebula in Orion’s belt is easy to spot.

Galaxies A galaxy is a system of billions of stars spin ning around a glactic center (where there is often a black hole). Through a small telescope, most galaxies look like fuzzy circles or ovals (or fuzzy lines if seen edgeon), but some have visible spirals. • What you need to see them: A small handful of galaxies can be seen with the naked eye and binoculars, but to see their structure you’ll need a telescope—the bigger, the better. • Examples to look for: On a clear, moonless night, the Andromeda Galaxy (also called M31) can be seen with the naked eye. With a telescope, you’ll get an edge-on view of this spiral galaxy.

The Milky Way The Milky Way is our own spiral galaxy—we are located in a spiral arm about two-thirds of the way out from the galactic center. The plane of the galaxy’s disk looks like a bright band across the sky, stretching from horizon to horizon. This part of the Milky Way looks brightest because it’s where most of the galaxy’s stars are located.

times. Only a few people (the astronauts who orbited the Moon for NASA’s Apollo Program, for example) have seen the far side of the Moon. The rest of us always view its near side. The Moon actually wobbles a bit in its orbit (an effect astronomers call libration), so over the course of a month, it’s possible to view up to 59% of the Moon’s surface.

Lunar Phases and When to Moongaze Half of the Moon (the side facing the Sun) is always lit, while the other half usually looks black in the night sky. Sometimes the dark side of the Moon becomes dimly visible from earthshine (sunlight that bounces off the Earth and hits the Moon). The sunlit face sweeps across the near side of the Moon in a 29.5-day cycle, so at different times of the month, we see different lunar phases. There are a few key terms astronomers use to talk about phases: • • • • • •

Waxing: The Moon is getting fuller Waning: The Moon is getting less full Quarter: The Moon is half full Crescent: The Moon is less than half full Gibbous: The Moon is more than half full New Moon: The Moon is not visible, as its orbit places it between the Earth and the Sun • Full Moon: The entire near side of the Moon is lit Before you plan to moongaze on a given night, make sure you know the current lunar phase. A Full Moon is actually a bad time for observing features on the Moon itself. Craters and mountain chains (see “Features of the Moon,” below) pop out in highest definition near the terminator (the line where the lit side of the Moon meets the dark side), so Quarter and Gibbous Moons are the best times to moongaze. If you know when the last New Moon occurred, you can use the table below to predict the phase: Days Into Lunar Cycle

Moon Phase

When the Moon Is Visible

1 day

New

Not visible

4 days

Waxing Crescent

8 a.m. to 10 p.m.

You can find the locations of many more stars, clusters, nebulae and galaxies with a detailed star or the online Messier Catalog. (For more resources, see Stargazing Resources.)

7 days

First Quarter

11 a.m. to 1 a.m.

The Moon

10 days

The Moon is often the biggest and brightest object in the night sky, and many of its surface features can be seen with the naked eye. It’s one of the most interesting celestial bodies to observe, whether through binoculars or a telescope.

Waxing Gibbous

2 p.m. to 4 a.m.

14 days

Full

5 p.m. to 7 a.m.

18 days

Waning Gibbous

8 p.m. to 10 a.m.

22 days

Last Quarter

11 p.m. to 1 p.m.

26 days

Waning Crescent

2 a.m. to 4 p.m.

• What you need to see it: On a clear night away from light pollution, the Milky Way is easily visible to the naked eye. • Examples to look for: The bright band of the Milky Way passes through the constellations Cassiopeia and Crux (the Southern Cross), and is brightest in the direction of Sagittarius (toward the galactic center).

Apennine Mountains

Plato crater

Mare Imbrium Oceanus Procellarum

Kepler crater

Mare Serenitatis

Mare Crisium

Mare Tranqilitatis

Copernicus crater

Tycho crater

What the Moon Looks Like

Features of the Moon Mare Nectaris

The Far vs. Near Side of the Moon Because the Moon is locked with the Earth’s orbit, the same side of the Moon—the near side—faces the Earth at all

Even when you look at the Moon with your naked eye, you’ll discern that there are two types of surfaces: bright ones (highlands, which are covered in craters) and darker ones (lowlands, which are filled with smooth, dark, volcanic rock). The “Man in the Moon” that some people see is a collection of lowlands that make up the eyes and mouth of a jolly cartoon face. With strong binoculars or a small telescope, you can see more features in good detail:

Stargazing

www.quamut.com • Craters: Holes of all sizes left from asteroids, mete oroids, and sometimes comets that impacted the Moon’s surface. These often have raised edges and central peaks (mountainous regions in the middle). • Maria: Large, dark, flat “seas” where lava has covered older, cratered surfaces. Maria is pronounced “MA-reeuh”; the singular is mare, pronounced “MA-ray.” • Rays: Bright lines radiating from craters. These rays are made of pieces of the lunar surface that were ejected when the crater was formed. The most prominent rays are visible around the Tycho crater. • Mountain ranges: Chains of mountain peaks that stretch across the surface of the Moon. The largest, the Apennines, can be seen with the naked eye near the terminator during the First Quarter Moon. • Rilles: Small valleys of lava flow that wind hundreds of miles across the Moon’s surface.

The Planets Planets are often the brightest objects in the sky and are easy to identify because, unlike stars, they don’t twinkle. All planets orbit the Sun, and all their orbits lie within the same plane—which means that all planets more or less follow the same path in the sky, close to the ecliptic. Some planets, such as Mars, seem to move backward along the ecliptic at certain times, a phenomenon called retrograde motion. If you see a bright object far from the ecliptic (near the constellation Cassiopeia, for example), it’s definitely not a planet. To learn which planets are visible on a given night, use a planet-finding chart or ephemeris (see Stargazing Tools).

Mercury Mercury has a heavily cratered surface like the Moon, but you won’t be able to see it clearly—it just looks like a bright dot. • Where it is: Closest to the Sun. The farthest Mercury ever gets from the Sun is 28°, so you can view it only during twilight, right after sunset or right before sunrise, barely above the horizon. • What you need to see it: Under good conditions you can spot Mercury with the naked eye, but usually you’ll need a telescope. Make sure there are no obstacles blocking the horizon in the direction of the Sun.

• What you need to see it: It’s easy to spot Mars with the naked eye by its orange-red color, but the planet is best observed through a small telescope.

Jupiter Jupiter is far from the Earth, but its colossal size makes it very bright. You can spot its larger moons all in a line, and if you observe several nights in a row, you’ll notice how the moons move with respect to the planet. Jupiter has a striped appearance due to its cloud belts, which have spots and irregularities—you can watch them rotate with Jupiter over the course of a night (Jupiter rotates once every 10 hours or so). • Where it is: Jupiter takes 12 years to make one orbit around the Sun, so its location in relation to the stars will be roughly the same over a year’s time. Just look up its current location in a planet-finding chart. • What you need to see it: You can find Jupiter easily with the naked eye, and you see up to four of its largest moons simply with a good pair of binoculars. A small telescope is best for viewing Jupiter’s atmospheric features, including the Great Red Spot (a giant swirling storm system).

There are a huge number of objects within our solar system besides planets. Composed mostly of rock, ice, and dust, they can be larger than Pluto or as small as a grain of sand.

Asteroids Asteroids are small, rocky bodies, most of which are located in the asteroid belt between Mars and Jupiter. They are very faint, and you’ll need a good ephemeris to find them with a small telescope. Of the thousands of known asteroids, Vesta is the easiest to observe and can sometimes been seen with the naked eye.

Comets are generally much farther away from the Sun than asteroids, but their elongated orbits bring them close to the Sun for short periods of time. Comets with shorter orbits—such as Halley’s comet, which returns every 76 years—pass the Sun more often than others. When comets come near the Sun, they grow two tails: a dust tail and an ion tail (which is less visible). Comets with clear tails are rarely visible to the naked eye. On any given night, more than a dozen comets can be seen through a telescope.

• Where it is: Saturn is farther out than Jupiter and also has a very long orbital period (almost 30 years). • What you need to see it: Saturn is bright to the naked eye, but you’ll need a small telescope to see its rings.

Uranus is faint, with cloudlike belts similar to Jupiter’s and Saturn’s. These belts are usually only visible with large, professional telescopes, though.

• Where it is: The next planet out from the Earth and, about every 26 months, the closest one to us.

Asteroids, Comets, and Meteors

Comets

Uranus

Mars looks like a bright red dot, and through a telescope you can spot its white polar caps and some of its distinct, dark surface markings.

• Where it is: Farthest from the Sun. • What you need to see it: You’ll spot Pluto only with a very powerful, professional telescope.

Saturn is a favorite among stargazers because of its rings. At different times of the year, you can catch the rings faint and close to edge-on, but most times they are brighter and more face-on. Even with a large telescope, you won’t be able to see structures within the rings. Saturn’s surface is covered by cloud belts, but less prominently than Jupiter’s.

Venus is often the brightest object in the sky—it emits a glowing, bluish-green light. Its atmosphere is so thick that you can’t see its surface, even with a telescope.

Mars

Even viewed through the Hubble Space Telescope, Pluto doesn’t look like much more than a bright dot. In 2006, the International Astronomical Union “demoted” Pluto from full planet status—it is now officially classified as a dwarf planet, though astronomers continue to debate its status.

Saturn

Venus

• Where it is: Closer to the Sun than the Earth. Venus is sometimes called the Morning Star or Evening Star because it stays relatively close to the Sun, and you can see it at dawn or dusk. • What you need to see it: You don’t need anything to spot Venus—not even dark skies. Venus is one of the few objects (besides the Sun and the Moon) that you can spot before the Sun has set or after it has risen.

Pluto

• Where it is: Very far from the Sun (19 times farther than the Earth). • What you need to see it: You’ll need binoculars to find Uranus among the stars, and a professional telescope to see its atmosphere. A modest telescope will reveal its pale, greenish sphere.

Neptune Neptune is very faint and looks featureless, except through the largest professional telescopes. • Where it is: Very far from the Sun (30 times farther than the Earth). • What you need to see it: You’ll need a small telescope to see Neptune at all. A modest-sized telescope will reveal it as a pale, bluish dot.

Meteors and Meteor Showers So-called “shooting stars” aren’t stars at all—they’re meteors, pieces of rock floating in space (most of which are smaller than a grain of sand) that burn up when they hit the Earth’s atmosphere, making bright streaks across the sky. Meteors hit the Earth all the time but are visible only at night. Occasionally, swarms of meteors hit the Earth, resulting in a close succession of shooting stars. These events are known as meteor showers, the most impressive of which are the Leonids (because they appear near the constellation Leo), which occur every year in November. During that time, you can spot up to 70 shooting stars in one hour.

Special Events in the Sky Most celestial objects can be seen on any given night, but some of the most spectacular events occur only rarely, and you’ll need to be well prepared in order to observe them.

Lunar Eclipses When the Moon is exactly on the opposite side of the Earth from the Sun (in the Earth’s shadow), sunlight passing through the Earth’s atmosphere will cast an eerie, reddish glow on the surface of the Moon. This event is a lunar eclipse and happens only during the Full Moon.

Stargazing

www.quamut.com Solar Eclipses When the Moon passes between the Earth and the Sun, it can block out some or all of the Sun for a moment. These events are called solar eclipses. There are a few varieties of solar eclipses, all of which occur only during the New Moon: • Total eclipse: In a total eclipse, the silhouette of the Moon completely covers the disk of the Sun. You may be able to see the solar corona, a halo of light surrounding the Sun. Because this totality can only been seen from a few locations on the surface of the Earth during each eclipse, some stargazers travel long distances to experience the best viewing conditions. • Annular eclipse: In an annular eclipse, the Sun and the Moon are exactly in line, but the Moon’s angular size is slightly smaller than the Sun’s. A bright ring of sunlight will be visible around the silhouette of the Moon. • Partial eclipse: In a partial eclipse, the Moon covers only a portion of the Sun. Observe solar eclipses with great care: looking directly at the Sun, even during an eclipse, can damage your eyes permanently. Regular sunglasses will not protect you, as they don’t filter harmful infrared light. Only a solar filter allows you to view an eclipse safely; you can also view an eclipse indirectly using a pinhole camera (a cardboard box with a small hole in it). NASA’s Eclipse Home Page describes how to make one and also provides a wealth of other information about when and where to view eclipses.

Occultations and Transits Occultation occurs when one celestial object passes directly in front of another. (Technically, solar and lunar eclipses are occultations.) Occultations of planets or the Moon passing in front of stars are neat to observe but require good planning: you can find a list of upcoming occultations on the website of the International Occultation Timing Association. Transits are occultations in which a smaller object passes in front of a larger one, such as Venus or Mercury passing in front of the Sun. These planetary transits look like small black circles moving across the disk of the Sun and, like solar eclipses, must be observed through a solar filter.

Sunspots Not all stargazing happens at night—the Sun is fascinating to observe during the day if you’re wearing proper eye protection. With a solar filter and small telescope, you can see sunspots (dark splotches on the Sun where the magnetic field is particularly strong). The number of visible sunspots changes over an 11-year solar cycle: you’ll see the most sunspots during solar maximum (while during solar minimum, you may not see any).

Aurorae (Northern and Southern Lights) Aurorae, stunning displays of colored lights that dance across the sky, are seen only at high latitudes near the poles. Depending on the hemisphere you’re in, aurorae are known as either the aurora borealis (northern lights) or aurora australis (southern lights). Aurorae occur when

charged particles from the Sun (the solar wind) hit the Earth’s upper atmosphere near the poles and cause it to glow. You’ll see better aurorae after stronger solar winds.

Manmade Satellites There are thousands of manmade satellites orbiting the Earth, many of which are too faint to see unaided by a telescope. However, some of the larger ones, such as the Space Shuttle and the International Space Station, are easy to spot: they look like bright, unblinking dots moving steadily across the sky more slowly than meteors but a little more quickly than airplanes. They’re most visible during the first and last hours of the night, when they emerge from the Earth’s shadow. On any given night, you can expect to see several satellites, and there are several good websites to help you figure out when and where to look (see Stargazing Resources).

Southern-Hemisphere Stargazing If you’re in the southern hemisphere, you’ll be able to see some the most spectacular objects in the sky, many of which are never visible in the northern hemisphere.

Rethinking Sky Motions In the southern hemisphere, the sky moves in the opposite way as in the northern hemisphere: the stars appear to rotate clockwise around the south celestial pole. Whereas the north celestial pole is marked by the North Star, there is no visible star right on the south celestial pole, so finding due south is a little more difficult than finding due north.

Southern Stars and Constellations If you’re stargazing in the southern hemisphere for the first time, you may be surprised to see the Moon and many familiar constellations upside-down. Orion, for example, looks as if he’s standing on his head. You’ll also get a chance to spot stars and constellations you’ve never seen before, such as: • Crux (Southern Cross): The best-known constellation in the southern sky, the Southern Cross looks more like a kite because its four stars are close together. You can use the Southern Cross to locate the south celestial pole: draw an imaginary line from the top of the cross through the bottom, and extend it about 30° (for help, see How to Get Oriented in the Night Sky), and you’ll be in the general area of the south celestial pole. • The Pointers: These are two very bright stars—Alpha Centauri (which is actually a triple star system, its three stars being the closest stars to the Earth) and Beta Centauri. The Pointers also lead to the south celestial pole: draw an imaginary line connecting them, and another line that cuts perpendicularly through the middle of this line. Where this second line intersects a line drawn through the long axis of the Southern Cross is roughly the location of the south celestial pole. You can also locate many more objects in the southern hemisphere by using a planisphere (see Stargazing Tools).

Magellanic Clouds On a good night, you can easily spot the stunning Magellanic Clouds with only the naked eye. They look like two small, wispy clouds (one slightly brighter and larger than the other) but are actually dwarf galaxies orbiting our own Milky Way. Both clouds are several times larger in the sky than the full Moon, and you can use your hand (see How to Get Oriented in the Night Sky) to measure their impressive sizes (the Large Magellanic Cloud is about 10° long, while the Small Magellanic Cloud is roughly 5° long). January is the best time to view them.

Stargazing Resources There is a large amount of literature on stargazing and astronomy, available in most bookstores and libraries. If you want improve your stargazing skills, it’s a good idea to subscribe to a magazine such as Sky & Telescope or Astronomy, which contain star charts, planet-finding charts, astrophotographs, and observation tips.

Amateur Astronomy Clubs Joining a local astronomy club is a great way to learn from experienced stargazers, try out new equipment, and get discounts on magazines and books. Most clubs hold regular observing sessions on weekends near the New Moon. To find a club in your area, see Sky & Telescope’s “Clubs & Organizations” page.

Astronomy Software Software packages make it easy to plan your stargazing efforts by looking up Moon phases, planet movements, and positions of stars and other objects, for any point in time— past, present, or future. Some software packages even allow you to control your telescope and an attached camera. Popular programs include: • Starry Night® (by Imaginova): A planetarium program with different versions for amateurs of different levels • RedShift™ (by Maris Technologies): A planetarium program with telescope control • SkyMap Pro (by SkyMap Software): A planetarium program and comprehensive collection of star charts • MaxIm DL™ (by Diffraction Limited): A camera control and astronomical imaging program

Online Resources These websites will help you figure out when and where you can find a variety of objects and events in the night sky: • International Occultation Timing Association: The best site for information about upcoming occultations. See www.lunar-occultations.com/iota/iotandx.htm. • Heavens Above: Info on locating manmade satellites and spacecraft. See www.heavens-above.com. • Clear Sky Clock: A tool to predict how clear the sky will be in your location during the course of a night. See www.cleardarksky.com/csk. • JPL Horizons System: A tool for generating ephemerides of planets, satellites, asteroids, and comets. See ssd.jpl.nasa.gov/?horizons. • This Week’s Sky at a Glance: A weekly description of Moon phases, visible planets, and transient objects, issued by Sky & Telescope magazine. See www. skyandtelescope.com/observing/ataglance. • Clubs & Organizations: A database provided by Sky & Telescope magazine to help you search for amateur astronomy clubs, museums, planetariums, observatories, and other organizations in regions across the world. See www.skyandtelescope.com/ community/organizations. • Telescopes 101: This guide to telescopes provides good information for when you’re trying to decide which telescope and accessories to buy. See www. telescopes.com/info/help.cfm. • Messier Catalog: A guide to locating nebulae, clusters, and galaxies. See seds.lpl.arizona.edu/messier. • Aurora Forecast: A site, run by the University of Alaska’s Geophysical Institute, that provides daily predictions of the solar wind and advice on when to catch good displays of the northern lights. See www. gedds.alaska.edu/AuroraForecast. • NASA’s Eclipse Home Page: Information about the times and best viewing locations of future (and past) eclipses, as well as information about how to view them safely. See sunearth.gsfc.nasa.gov/eclipse/ eclipse.html.