Next, suppose that without changing the hour of observation he changes the date, and instead of observing on the 20th of March he observes on the 5th. Then he will notice precisely the same difference that was manifest when his observation was made an hour too early on March 20th—i. e., some of the eastern stars on the chart will not yet have risen, and other stars, not on that particular chart, will be visible in the west. Although at first all this may be a little confusing to the beginner, he will soon find that he can make due allowance for the changes of aspect. The whole matter becomes very simple when it is remembered that the heavens have a double revolution toward the west; one of these revolutions, due to the earth’s rotation on its axis, being effected in twenty-four hours, and the other, due to the earth’s revolution round the sun, requiring an entire year. One hour of the daily revolution (represented by an hour of right ascension) produces the same effect on the position of the stars as two weeks of the annual revolution; or two hours of the first correspond to one month of the second.
If the observations are made at a later date or a later hour than those indicated on the chart, the changes will occur in the reverse order—i. e., western stars will have disappeared and eastern stars will have come up into view.
I particularly wish to impress upon the beginner the needlessness of being troubled about these discrepancies. He can avoid all possibility of perplexity by fitting his observations to the exact times of the charts. As I have already said, a difference of a few degrees in his latitude on the earth may be disregarded. The charts, with a slight allowance for the shift of position of the extreme northern and southern stars, are available for any of the middle latitudes of the northern hemisphere. And if the effects of a change of hour or date prove in the least confusing, the beginner has only to await the given date and the given hour, and all will be clear. Then, as soon as he has become familiar with a few of the leading constellations, the others, which in themselves are not so easily recognizable, will fall into their proper places, after which there can be no possibility of confusion. In fact, much less effort is required to become familiar with the aspect of the starry sky than is demanded for a similar acquaintance with the fundamental data of botany, mineralogy, geology, or any other of the observational branches of natural science.
It was at first the intention to indicate the course of the Milky Way on the circular charts by dotted outlines, but this was abandoned in view of the restricted space. Any one can easily trace the meanderings and branchings of this starry scarf, the contemplation of which carries the mind to greater heights of intellectual perspective than any other phenomenon of the world of matter. If the reader has the good-fortune to be situated where artificial lights do not interfere with the splendor of the heavens, he can observe the course of the Milky Way on any clear night; and, if he possesses skill in delineation, he may make charts of it and its offshoots which will be of real value. Better still if he has the means of photographing it. Here is a non-mathematical field of astronomy which is ripe for the harvest, and in which the laborers are few. The Milky Way is so full of wonders that centuries of observation and study cannot exhaust them. There is nothing more impressive than to see how it often follows curves of lucid stars as if some mysterious attraction were drawing it toward them; and yet it itself consists of stars.
A few more words of practical advice to the beginner. Let him, at first, confine himself to the bright and conspicuous stars and the striking groups shown in the charts, assigning each to its proper constellation. When he has become familiar with these in their broadest aspects, he can turn to the charts at the end of the book and familiarize himself with the constellation boundaries. After that, if he wishes to go further, as he almost certainly will, he can obtain a large star atlas, furnish himself with a telescope, and open up a new side of his life which will make him rejoice to be, for a few short years, a dweller on a planet inhabited by beings intelligent enough to lift their eyes above the horizon and to feed their minds with the inspirations of the universe.
Yet another thing, which may be a novelty to many, and which is sure to afford unexpected pleasure—when you have fairly learned the constellations, take a mirror and study them by reflection. This is a counsel of intimacy. Orion will seem less remote and more comprehensible when his living image is enclosed in a frame, which you can hold on your lap like an album. There is something startling in the sight of the starry heavens under your feet. I once enjoyed the sensation in perfection while stalking deer in a boat at midnight on the placid bosom of a forest pond. The water was as motionless as so many acres of black glass, and I forgot to look for the deer, in the shaft of light from the hooded “flare” at the bow, when we seemed to be drifting out into an ocean of ether, in the middle of the sky, with stars below as well as stars above. When we silently crossed the pond, and got far from the shores, the sensation was overpowering; it took one’s breath away. We drifted right over the Milky Way, and Vega, Altair, and the “Northern Cross” gleamed beneath the keel. Be sure that your mirror is freshly silvered and clean, and remember the reversals of position which all reflections produce. If you hold the mirror before you inclined downward, the position of objects in the sky will be reversed top for bottom; if you hold it inclined upward, so as to see objects behind your head, they will be reversed right for left. With these precautions you will find the mirror a great convenience for studying constellations which are nearly overhead. It is the principle of the “diagonal prism” employed with telescopes, and of the hand-mirrors used by many visitors at the Vatican Palace to view with comfort the ceiling pictures of Michael Angelo in the Sistine Chapel. Thus the sky becomes an atlas, and you can study its living charts at leisure.
ROUND THE YEAR WITH THE STARS
I
THE EVENING SKY AT THE VERNAL EQUINOX
The year has its morning no less unmistakable in its characteristic features than the dawn of the day. The earth and all of its inhabitants feel the subtle influences of the dawning year, and Nature awakes at their touch. This annual morning comes when the sun transits the equator, moving north, at the beginning of his long summer tour, about the 20th of March. This is the epoch of the Vernal Equinox, when the springs of life begin, once more, to flow. Then the sun truly rises on the northern hemisphere. Then the mighty world of the north, which Providence has made the chief abode of vital organisms on this planet, rouses itself and shakes off the apathy of winter, and men, animals, and plants, each after their manner, renew their activities, and in many cases their very existence. This annual reawakening is one of the profoundest phenomena of nature, and there are secrets in it which science has not yet penetrated.
Bliss Carman has beautifully pictured the terrestrial charms of the vernal season in his “Spring’s Saraband”: