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Star Watch: The Amateur Astronomer's Guide to Finding, Observing, and Learning about Over 125 Celestial Objects
     

Star Watch: The Amateur Astronomer's Guide to Finding, Observing, and Learning about Over 125 Celestial Objects

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by Philip S. Harrington
 

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Your Passport to the Universe

The night sky is alive with many wonders—distant planets, vast star clusters, glowing nebulae, and expansive galaxies, all waiting to be explored. Let respected astronomy writer Philip Harrington introduce you to the universe in Star Watch, a complete beginner's guide to locating, observing, and understanding these celestial

Overview

Your Passport to the Universe

The night sky is alive with many wonders—distant planets, vast star clusters, glowing nebulae, and expansive galaxies, all waiting to be explored. Let respected astronomy writer Philip Harrington introduce you to the universe in Star Watch, a complete beginner's guide to locating, observing, and understanding these celestial objects. You'll start by identifying the surface features of the Moon, the banded cloud tops of Jupiter, the stunning rings of Saturn, and other members of our solar system. Then you'll venture out beyond our solar system, where you'll learn tips and tricks for finding outstanding deep-sky objects from stars to galaxies, including the entire Messier catalog—a primary goal of every serious beginner.

Star Watch features a detailed physical description of each target, including size, distance, and structure, as well as concise directions for locating the objects, handy finder charts, hints on the best times to view each object, and descriptions of what you'll really see through a small telescope or binoculars and with the naked eye.

Star Watch will transport you to the farthest depths of space—and return you as a well-traveled, experienced stargazer.

Editorial Reviews

From the Publisher
* One of the first questions prospective purchasers ask when looking at telescopes is “what can I see with it?” It is certainly a valid question but one that sales staff can only answer in very broad terms with regard to the types of objects and detail visible with a given aperture. Faced with a dark sky and a bewildering number of stars, beginners soon realize that those objects often prove quite elusive and expert guidance at the eyepiece is essential. Star Watch is designed to take the reader by the hand and guide him or her on a memorable journey through the universe.
Encompassing both binocular and small to medium aperture telescope observing, Phil Harrington’s latest book appeals to a wide spectrum of the amateur astronomy community and provides a firm grounding in all aspects of observational astronomy. At some point, most amateur astronomers come to appreciate that one or more facets appeal most and beginners too must discover in which direction their interests lie.
Your journey starts close to home with our nearest neighbour, the Moon. Here, the author splits the lunar month into partial phases with the most prominent features described and accompanied by labeled photographs taken by the author. Virtually all budding astronomers are also interested in the planets. Many years ago, my first views of Saturn and Jupiter knocked me out and whoever was lucky enough to see mars on its closest approach last autumn through a good telescope will not easily forget the brilliant detail visible on the Red Planet. Phil Harrington seems to have pitched the level of information just right for those taking their first views of the planets and also provides useful tips on observing asteroids, comets and the Sun.
The latter two-thirds of Star Watch is devoted to deep sky, a term referring to objects lying outside our solar system. Most of the deep sky objects comprise those within the Messier Catalogue accompanied by a fair sprinkling of some of the most attractive double stars and NGC objects. It is an eclectic mix of clusters, galaxies, nebulae and stars that is sure to please all observers. The list is divided over the four seasons and further sub-divided into Sky Windows, each Sky Window with its own map showing the location of the objects within. I could not find any reference to the limiting star magnitude of the Sky Windows but it seems to be magnitude of the Sky Windows but it seems to be magnitude 7. Serving up the night sky in bite-size chunks is an excellent way keeping the reader focused on a particular area instead of wandering all over the sky. Again, the level of information in the text on where and what to look for is spot on for inexperienced observers and the inclusion of a “WOW!” FACTOR rating indicates how impressive each object is through binoculars, small telescopes and medium telescopes.
I tested some of the summer Sky Windows using my 15 x 50 binoculars and a 90mm telescope and found the objects relatively easily using the principal maps. The all-sky insets are too small to be of any real practical use but do help to correlate the celestial location of a particular Sky Window with the larger seasonal and key maps at the beginning of each chapter.
So, is Star Watch the ideal companion for people starting out in this wonderful hobby, or indeed those with limited observing experience? Yes, it most certainly is! By the time a beginner completes the lunar, planetary and deep sky explorations using this book as a guide, he or she will be an accomplished amateur astronomer ready to delve even deeper into the universe around us and, with a certificate to prove it. Complete the four seasonal lists, record your observations and submit these to the author to obtain your very own numbered and signed Star Watcher certificate!¾Reviewed by Gordon Nason (Astronomy & Space, August 2004)

“…has infectious enthusiasm that makes people want to buy a telescope

Product Details

ISBN-13:
9780471418047
Publisher:
Turner Publishing Company
Publication date:
07/11/2003
Edition description:
First Edition
Pages:
312
Sales rank:
1,196,781
Product dimensions:
7.53(w) x 9.18(h) x 0.72(d)

Read an Excerpt

Star Watch

The Amateur Astronomer's Guide to Finding, Observing, and Learning about Over 125 Celestial Objects
By Philip S. Harrington

John Wiley & Sons

ISBN: 0-471-41804-8


Chapter One

Your Passport to the Stars

Since before the dawn of history, our ancestors have gazed skyward in awe and wonder. At first, the universe seemed cold, inhospitable, and filled with danger. Was the sky populated by gods of the Moon, the Sun, and planets who ruled mortals and could destroy or spare Earth with a mere wave of their hands? Did our very lives depend on their whimsy? As time evolved, curiosity grew about the exact nature of the Sun, the Moon, and other sky objects. The ancient Babylonians, Assyrians, and Greeks were among the first civilizations to study the sky in an attempt to understand how these objects influenced the course of human events. Their studies gave birth to the pseudoscience of astrology but more importantly also laid the basic foundation for the science of astronomy. Indeed, many of the names for stars and star patterns, called constellations, that we still use today trace their origin back to this early epoch.

Perhaps the greatest study of the universe by one of our ancient ancestors was performed by the Greek astronomer Claudius Ptolemaeus, or Ptolemy for short. While living in Egypt in the second century A.D., Ptolemy devised a scheme that predicted the movements of the Sun, the Moon, and planets in our sky with amazingaccuracy. Ptolemy's geocentric system, which placed Earth at the center of the universe, remained the dominant model for more than a thousand years, until the European Renaissance in the sixteenth and seventeenth centuries.

Today, we know the true order of the universe. No longer populated by fearsome gods and goddesses, our universe plays host to stars and galaxies, planets and moons, and many other wonders that beckon us to stare skyward with the same awe and wonder felt by the first astronomers. We know that Earth is not at the center of the universe, and in fact that the universe really has no center at all. Instead, the universe is populated by millions, if not billions, of galaxies (Figure 1.1), each a huge system of stars. With rare exception, all galaxies are seemingly racing away from one another, motions induced by the Big Bang, which created the universe some 15 billion years ago. Some are independently traveling through the universe, while others travel in groups and clusters.

Each galaxy, including our own Milky Way, is made up of millions, if not billions, of individual stars. Many stars exist alone, while others formed in pairs, trios, or larger groupings. The largest star groupings are referred to as star clusters (Figure 1.2). Depending on the type, a cluster may hold anywhere from a dozen to half a million stars!

Interspersed throughout many galaxies are large clouds of gas and dust called nebulae (Figure 1.3). Some nebulae may be thought of as stellar nurseries, marking regions where new stars are forming. Other nebulae are stellar corpses, all that remain of once powerful suns.

Closer to home, our star, the Sun, serves as the focal point of a collection of comparatively small celestial bodies that we collectively call the solar system. In addition to the Sun, the solar system includes the nine planets-Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto-as well as many moons, asteroids, comets, and meteoroids.

All of these objects are waiting for you in the sky. But gazing skyward, trying to identify one from another or simply knowing where to look, can prove to be a daunting task for someone brand-new to the universe! Where is everything? Which star is which? Are there any planets out tonight? I just bought a new telescope; what should I look at first? And how do I use it?

All good questions. Where do you find the answers? I hope you find them here! Think of this book as your passport to places that few of the world's population are even aware exist. You and I are heading off to the farthest depths of space.

The Sky: An Overview

At first glance, the sky appears to be a mishmash of points of light, seemingly scattered at random and impossible to fathom. But the sky isn't as chaotic as it seems at first. It has a clear order that just takes a little time to understand. Let's begin with some basics.

Sky Motions

Watching the stars move silently overhead at night, we can easily see how Ptolemy and other ancient skywatchers came away with the idea that everything circled Earth. Instead, we know that this effect is caused by Earth rotating on its axis, an imaginary line that passes through the center of Earth, with the North Pole at one end and the South Pole at the other. This motion, called daily or diurnal motion (Figure 1.4), causes the Sun, the Moon, planets, and stars to appear as though they rise in the east, move across the sky, and set in the west. Daily motion also opens our sky window toward different stars at different times of the night.

In addition to rotating on its axis, Earth also revolves around the Sun, taking one year to complete the trip. We call this annual motion. It takes Earth 365 days 5 hours 49 minutes to complete a revolution of the Sun, at an average speed of 66,500 miles (107,000 kilometers) per hour or 18.46 miles (29.73 kilometers) each second!

Annual motion also opens our sky window onto different stars and constellations at different seasons of the year. Those stars and constellations seen on winter evenings, for instance, are called the winter stars, and are completely different from those visible on summer evenings. During the summer and winter months, the night side of Earth is aimed toward different portions of the plane of our galaxy, where the gentle rifts of the Milky Way stretch across the sky to give spectacular views of rich star clouds and subtle nebulae. The spring and fall skies open away from the obscuring dust clouds of our galaxy to reveal a universe that is full of other distant galaxies. Figure 1.5 shows Earth in its annual trek around the Sun as compared with the seasonal constellations.

Finally, Earth also wobbles like a toy top in a motion called precession. If you've spun a top, you know that its axis of rotation is usually perpendicular to the surface on which it is spinning. But give it a slight nudge and the top will begin to tip over. Still spinning, the top attempts to right itself, in the process causing its axis of rotation to trace out a circle. The combined effect of Earth slightly bulging at the equator, combined with gravitational nudges from the Sun and the Moon, has nudged Earth enough to set it into a slow wobble. Precession is barely noticeable compared to our planet's rotation and revolution, taking some 26,000 years for Earth to complete just one twist. While this shift cannot be detected with the naked eye over the brief course of a human lifetime, the change is obvious across the span of human history. Right now, the Earth's North Celestial Pole is aimed almost directly at the star Polaris, also known as the North Star. But back in the time of ancient Egypt, the pharaohs saw the night sky turning about the star Thuban in our constellation Draco the Dragon. In 13,000 years, the star Vega in the constellation Lyra will be closest to the North Celestial Pole.

Star Brightness

When astronomers talk about how bright something appears in the sky, they are referring to that object's magnitude. The magnitude system dates back over 2,000 years to the Greek astronomer Hipparchus, who was first to survey the night sky and devise a system for categorizing stars according to their brightness. His method was quite simple. The brightest stars visible to the eye were labeled 1st magnitude, while the faintest stars were 6th magnitude. The remaining stars fell somewhere in between. In the Hipparchus magnitude system, the larger the magnitude number, the fainter the star. The magnitude system in place today is far more precise but still strongly reminiscent of Hipparchus's. We still use the basic 1st-through-6th magnitude designations, but we now specify that a 1-magnitude jump (say from 1st to 2nd, or 2nd to 3rd) corresponds to a change in brightness of 2.5 times. Therefore a 1st-magnitude star is 2.5 times brighter than a 2nd-magnitude star, while a 2nd-magnitude star is 2.512 times brighter than a 3rd-magnitude star. By this method, a 1st-magnitude star is about 6.3 times brighter than a 3rd-magnitude star (2.512 x 2.512 = 6.310), about 15.8 times brighter than a 4th-magnitude star (2.512 x 2.512 x 2.512 = 15.85), about 40 times brighter than a 5th-magnitude star (2.512 x 2.512 x 2.512 x 2.512 = 39.81), and so on. A 5-magnitude jump, say from 1st to 6th magnitude, equals a change in brightness of exactly 100 times.

Astronomers of the nineteenth century refined and expanded Hipparchus's magnitude system to include the very brightest and very faintest celestial objects, so the scale doesn't stop at 1st or 6th magnitude. A zero-magnitude object is 2.512 times brighter than a 1st-magnitude object, while negative-value objects are brighter still. The Sun, for instance, is magnitude -26. At the same time, stars that are too faint to be seen with the naked eye have magnitude values greater than 6th magnitude. As you can see from Figure 1.6, binoculars reveal stars to about 9th magnitude, a 6-inch (15-cm) telescope to 13th magnitude, and larger telescopes deeper still. The Hubble Space Telescope can record stars as faint as 30th magnitude, about 19 billion times fainter than the Sun!

Magnitudes only refer to how bright objects appear in our sky. Just because a star looks bright in the sky doesn't mean that it is big, of course. For example, the Sun is the brightest object in our sky, but pull back an appreciable distance and it quickly disappears into the crowd. The Sun is only bright because it is so close. A star's apparent brightness, or magnitude, depends on two factors: its intrinsic luminosity and distance. To express a star's true brightness, astronomers use the term luminosity. The luminosity scale uses the Sun as its baseline value of 1.0. Stars with luminosities greater than 1.0 are intrinsically brighter than the Sun, while those less than 1.0 are dimmer. Sirius, the brightest star in the sky, has a luminosity of 24, meaning that it is 24 times more luminous than the Sun, while the star Deneb in Cygnus has a luminosity of 24,000. So why does Sirius look brighter in our sky than Deneb? Measurements show that Sirius lies only 9 light-years away, while Deneb is more than 3,200 light-years from us.

Star Sizes and Distances

The sizes of stars, planets, and other objects are referred to in two different ways. One is a measure of their actual size. The Moon, for instance, measures 2,159 miles across (3,476 kilometers), while the Sun is 864,400 miles (1,392,000 kilometers) in diameter, and so on.

Apparent size, or how large something appears in the sky, is expressed in angular degrees, which can be further divided into arc-minutes and arc-seconds. Figure 1.7 offers an example. The Andromeda Galaxy apparently spans 5º in length in photographs. This is considerably more than the Moon or Sun, each of which measures half a degree, or 30 arc-minutes (abbreviated 30'). Sky objects that are even smaller than 1 arc-minute are measured in arc-seconds. There are 60 arc-minutes (60') in 1 degree and 60 arc-seconds in 1 arc-minute.

Values in miles and kilometers quickly become too cumbersome to use when talking about the actual distances to the stars, so astronomers refer to distances in light-years. One light-year is equal to the distance that a beam of light would travel in space in one Earth year, more than 5.87 trillion miles (9.45 trillion kilometers), or 186,000 miles per second (300,000 kilometers per second)! The Andromeda Galaxy, usually regarded as the most distant object visible to the naked eye, lies about 2.9 million light-years away. That means the light we would see from it tonight, traveling at 186,000 miles every second, took 2.9 million years to get here! That translates to a distance of 17 billion miles (27.4 billion kilometers)!

Astronomers use very precise tools to measure apparent sizes of and distances between objects in the sky with great accuracy, but you and I were born with a handy tool that we can use to approximate those same values. It's your hand! Take a look at Figure 1.8. It turns out that the ratio of the size of the human hand to the length of the arm is proportional for everyone, regardless of age or gender. For instance, at arm's length, your fist covers 10º. Your middle three fingers extended as in a Scout salute cover 5º of sky, the same span as the pointer stars at the end of the bowl of the Big Dipper. The span between your pinky finger and forefinger equals 15º, while the span between your thumb and pinky equals 25º. (Note that some people can stretch their hands more than others, which may throw this last measurement off a bit. To find out your hand span, hold it up against the Big Dipper. If your finger and thumb can cover its length fully, your span is 25º; a little less, and it's probably closer to 20º.)

When you get to the later chapters that discuss each seasonal sky, remember this "handy" method for finding distances between stars and constellations. It makes getting around the sky much easier.

Star Positions

If you were to give me directions to your home, you might take me from a major highway or thoroughfare to a secondary road, and finally to your street and house number. That is pretty much how most amateur astronomers find objects in the sky. They begin at a major constellation, travel to a particular star in the pattern, then follow fainter stars to the target itself. This technique, called star hopping, is discussed later in this chapter.

While these methods work fine out in the field, they can be cumbersome when trying to list either an earthly location or celestial object in a data catalog. Instead, geographers have divided up Earth into a north-south and eastwest coordinate system called latitude and longitude, respectively. Astronomers have similarly divided up the sky into a north-south, east-west coordinate system. Rather than use longitude and latitude, celestial coordinates refer to right ascension and declination.

Let's look at declination first. Just as latitude is the measure of angular distance north or south of the Earth's equator, declination (abbreviated Dec.) specifies the angular distance north or south of the celestial equator. The celestial equator is simply the projection of Earth's equator up into the sky. If we were positioned at 0º latitude on Earth (the equator), we would see 0º declination pass directly through the zenith, while 90º north declination (the North Celestial Pole) would be overhead from the Earth's North Pole.

Continues...


Excerpted from Star Watch by Philip S. Harrington Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

Meet the Author

PHILIP S. HARRINGTON is a contributing editor for Astronomy magazine and has been published in most leading astronomy periodicals. He is also the author of Star Ware, Touring the Universe through Binoculars, and Eclipse!, all published by Wiley.

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Star Watch: The Amateur Astronomer's Guide to Finding, Observing, and Learning about Over 125 Celestial Objects 1.5 out of 5 based on 0 ratings. 2 reviews.
Anonymous More than 1 year ago
She grins. "I will never say it."
Anonymous More than 1 year ago
"And what would that be?"