Chapter I: Preface

By the introduction of a complete series of star maps, drawn specially for the use of the amateur and distributed through the body of the work, thus facilitating consultation, it is believed that this book makes a step in advance of its predecessors. The maps show all of the stars visible to the naked eye in the regions of sky represented, and, in addition, some stars that can only be seen with optical aid. The latter have been placed in the maps as guide posts in the telescopic field to assist those who are searching for faint and inconspicuous objects referred to in the text. As the book was not written for those who possess the equipment of an observatory, with telescopes driven by clockwork and provided with graduated circles, right ascensions and declinations are not given. All of the telescopic phenomena described are, however, represented in the maps. Star clusters are indicated by a conventional symbol, and nebulæ by a little white circle; while a small cross serves to mark the places where notable new stars have appeared. The relative magnitudes of the stars are approximately shown by the dimensions of their symbols in the maps, the smaller stars being represented by white dots and the larger by star-shaped figures.

In regard to binary stars, it should be remembered that, in many cases, their distances and angles of position change so rapidly that any statement concerning them remains valid only for a few years at the most. There is also much confusion among the measurements announced by different authorities. In general, the most recent measurements obtainable in 1900 are given in the text, but the observer who wishes to study close and rapid binaries will do well to revise his information about them as frequently as possible. An excellent list of double stars kept up to date, will be found in the annual Companion to the Observatory, published in London.

In the lunar charts the plan of inserting the names of the principal formations has been preferred to that usually followed, of indicating them only by numbers, accompanied by a key list. Even in the most detailed charts of the moon only a part of what is visible with telescopes can be shown, and the representation, at best, must be merely approximate. It is simply a question of what to include and what to omit; and in the present case the probable needs of the amateur observer have governed the selection--readiness and convenience of reference being the chief aim.

It should, perhaps, be said here that the various chapters composing this book--like those of "Astronomy with an Opera-glass"--were, in their original form, with the single exception of Chapter IX, published in Appletons' Popular Science Monthly. The author, it is needless to say, was much gratified by the expressed wish of many readers that these scattered papers should be revised and collected in a more permanent form. As bearing upon the general subject of the book, a chapter has been added, at the end, treating on the question of the existence of planets among the stars. This also first appeared in the periodical above mentioned.

In conclusion, the author wishes for his readers as great a pleasure in the use of the telescope as he himself has enjoyed.

G. P. S.

BOROUGH OF BROOKLYN, NEW YORK, _January, 1901_.

CONTENTS

CHAPTER I PAGE

THE SELECTION AND TESTING OF A GLASS 1

How to get a good telescope--Difference between reflectors and refractors--How a telescope is made achromatic--The way to test a telescope on stars.

CHAPTER II

IN THE STARRY HEAVENS 19

Orion and its wonders, Lepus, Canis Major, Argo, Monoceros, Canis Minor, and the Head of Hydra.

CHAPTER III

FROM GEMINI TO LEO AND ROUND ABOUT 38

The zodiacal constellations Gemini, Cancer, and Leo, and their neighbors Auriga, the Lynx, Hydra, Sextans, and Coma Berenices.

CHAPTER IV

VIRGO AND HER NEIGHBORS 57

Crater and Corvus, Hydra, Virgo, the "Field of the Nebulæ," Libra, Boötes, and the great Arcturus, Canes Venatici, and Corona Borealis.

CHAPTER V

IN SUMMER STAR-LANDS 75

Scorpio and its red-green gem, Ophiuchus, Sagittarius, Scutum Sobieskii, Capricornus, Serpens, Hercules, Draco, Aquila, and Delphinus.

CHAPTER VI

FROM LYRA TO ERIDANUS 97

Lyra and its brilliant Vega, Cygnus, Vulpecula, Aquarius, Equuleus, Pegasus, Cetus, and Eridanus.

CHAPTER VII

PISCES, ARIES, TAURUS, AND THE NORTHERN MARS 117

The first double star ever discovered, the Pleiades and their photographic wonders, the Royal Family of the Sky, Andromeda, Cassiopeia, Perseus and Cepheus, Ursa Major, Camelopardalus, Ursa Minor, and the Pole Star.

CHAPTER VIII

SCENES ON THE PLANETS 139

Jupiter, its belts and its moons--Saturn, the ringed planet--Saturn's moons and Roche's limit--Mars and its white polar caps and so-called seas and continents--Venus and her atmosphere--The peculiar rotations of Venus and Mercury.

CHAPTER IX

THE MOUNTAINS AND PLAINS OF THE MOON AND THE SPECTACLES OF THE SUN 156

Peculiarities of the lunar landscapes--The so-called seas, the craters, the ring mountains, the inclosed plains, the mountain ranges, Tycho's mysterious streaks, and other lunar features described--How to view the sun and its spots.

CHAPTER X

ARE THERE PLANETS AMONG THE STARS? 183

Significance of Dr. See's observations--Why our telescopes do not show planets circling around distant suns--Reasons for thinking that such planets may exist--The bearing of stellar evolution on the question.

PLEASURES OF THE TELESCOPE