Through the Telescope

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James Baikie. Through the Telescope

Through the Telescope

Table of Contents

PREFACE

LIST OF ILLUSTRATIONS

THROUGH THE TELESCOPE

CHAPTER I

CHAPTER II

CHAPTER III

CHAPTER IV

CHAPTER V

CHAPTER VI

CHAPTER VII

CHAPTER VIII

CHAPTER IX

CHAPTER X

CHAPTER XI

CHAPTER XII

CHAPTER XIII

CHAPTER XIV

CHAPTER XV

APPENDIX I

APPENDIX II

INDEX

A

B

C

D

E

F

G

H

I

J

K

L

N

O

P

R

S

T

U

V

W

Y

Z

Отрывок из книги

James Baikie

Published by Good Press, 2022

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FIG. 12.—8-INCH REFRACTOR ON EQUATORIAL MOUNTING.

As a matter of policy, one can scarcely advise the beginner to make his first essay with a reflector. Its adjustments, though simple enough, are apt to be troublesome at the time when everything has to be learned by experience; and its silver films, though much more durable than is commonly supposed, are easily destroyed by careless or unskilful handling, and require more careful nursing than the objective of a refractor. But, having once paid his first fees to experience, the observer, if he feel so inclined, may venture upon a reflector, which has probably more than sufficient advantages to make up for its weaker points. First and foremost of these advantages stands the not inconsiderable one of cheapness. A 10½-inch reflector may be purchased new for rather less than the sum which will buy a 4-inch refractor. True, the reflector has not the same command of light inch for inch as the refractor, but a reflector of 10½ inches should at least be the match of an 8-inch refractor in this respect, and will be immeasurably more powerful than the 4-inch refractor, which comes nearest to it in price. Second stands the ease and comfort so conspicuous in observing with a Newtonian. Instead of having almost to break his neck craning under the eye-piece of a telescope pointed to near the zenith, the observer with a Newtonian looks always straight in front of him, as the eye-piece of a reflector mounted as an altazimuth is always horizontal, and when the instrument is mounted equatorially, the tube, or its eye-end, is made to rotate so that the line of vision may be kept horizontal. Third is the absence of colour. Colour is not conspicuous in a small refractor, unless the objective be of very bad quality; but as the aperture increases it is apt to become somewhat painfully apparent. The reflector, on the other hand, is truly achromatic, and may be relied upon to show the natural tints of all objects with which it deals. This point is of considerable importance in connection with planetary observation. The colouring of Jupiter, for instance, will be seen in a reflector as a refractor can never show it.

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