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A Field Book of the Stars.
by William Tyler Olcott.
Considering the ease with which a knowledge of the constellations can be acquired, it seems a remarkable fact that so few are conversant with these time-honored configurations of the heavens. Aside from a knowledge of "the Dipper" and "the Pleiades," the constellations to the vast majority, are utterly unknown.
To facilitate and popularize if possible this fascinating recreation of star-gazing the author has designed this field-book. It is limited in scope solely to that purpose, and all matter of a technical or theoretical nature has been omitted.
The endeavor has been to include in these pages only such matter as the reader can observe with the naked eye, or an opera-gla.s.s.
Simplicity and brevity have been aimed at, the main idea being that whatever is bulky or verbose is a hindrance rather than a help when actually engaged in the observation of the heavens.
The constellations embraced in this manual are only those visible from the average lat.i.tude of the New England and Middle States, and owe their place in the particular season in which they are found to the fact that in that season they are favorably situated for observation.
With this brief explanatory note of the purpose and design of the book, the author proceeds to outline the scheme of study.
SCHEME OF STUDY.
The table of contents shows the scheme of study to be pursued, and to facilitate the work it is desirable that the student follow the therein circ.u.mscribed order.
A knowledge on the part of the reader of Ursa Major, or "the Dipper"
as it is commonly called, and "the Pleiades," the well-known group in Taurus, is presupposed by the author.
With this knowledge as a basis, the student is enabled in any season to take up the study of the constellations. By following out the order dictated, he will in a few nights of observation be enabled to identify the various configurations making up the several constellations that are set apart for study in that particular season.
A large plate, showing the appearance of the heavens at a designated time on the first night of the quarter, is inserted before each season's work. This should be consulted by the student before he makes an observation, in order that he may obtain a comprehensive idea of the relative position of the constellations, and also know in what part of the heavens to locate the constellation which he wishes to identify.
A knowledge of one constellation enables the student to determine the position of the next in order. In this work, the identification of each constellation depends on a knowledge of what precedes, always bearing in mind the fact that each season starts as a new and distinct part to be taken by itself, and has no bearing on that which comes before.
The diagrams, it will be observed, are grouped under the seasons, and they indicate the positions of the constellations as they appear at 9 o'clock P.M. in mid-season.
To facilitate finding and observing the constellations, the student should face in the direction indicated in the text. This applies to all constellations excepting those near the zenith.
The four large plates are so arranged that the observer is supposed to be looking at the southern skies. By turning the plate about from left to right, the eastern, northern, and western skies are shown successively.
On many of the diagrams the position of nebul is indicated. These are designated by the initial letter of the astronomer who catalogued them, preceded by his catalogue number, as for instance 8 M. signifies nebula number 8 in Messier's catalogue.
The magnitudes a.s.signed to the stars in the diagrams are derived from the Harvard Photometry. When a star is midway between two magnitudes the numeral is underlined, thus _2_, indicates a star of magnitude 2.5.
If a star's magnitude is between 1 and 1.5 it is regarded as a first-magnitude star. If it lies between 1.5 and 2 it is designated second magnitude.
THE CONSTELLATIONS OF SPRING.
[Ill.u.s.tration: Map showing the princ.i.p.al stars visible from Lat. 40 N. at 9 o'clock April 1st.]
URSA MAJOR (ersa ma-jor)--THE GREAT BEAR. (Face North.)
LOCATION.--Ursa Major is probably the best known of the constellations, and in this work I presuppose that the reader is familiar with its position in the heavens. It is one of the most noted and conspicuous constellations in the northern hemisphere, and is readily and unmistakably distinguished from all others by means of a remarkable cl.u.s.ter of seven bright stars in the northern heavens, forming what is familiarly termed "The Dipper."
The stars a and are called the pointers, because they always point toward the Pole Star, 28 distant from a.
Alioth is very nearly opposite Shedir in Ca.s.siopeia, and at an equal distance from the Pole. The same can be said of Megres, in Ursa Major, and Caph, in Ca.s.siopeia.
The star ? is at the tip of the Bear's nose. A clearly defined semicircle begins at ? and ends in the pair ? and ? at the extremity of the Bear's right fore paw. This group of stars resembles a sickle.
Note little Alcor close to Mizar. This star was used by the Arabs as a test of good eyesight.
Mizar and Alcor are known as the horse and his rider.
This plate shows the Bear lying on his back, his feet projected up the sky; three conspicuous pairs of stars represent three of his four feet.
The Chaldean shepherds and the Iroquois Indians gave to this constellation the same name. The Egyptians called it "The Thigh."
a and ? are moving through s.p.a.ce in a contrary direction to the remaining five stars in "The Dipper."
[Ill.u.s.tration: URSA MAJOR]
URSA MINOR (er-sa mi-nor)--THE LITTLE BEAR. (Face North.)
LOCATION.--The two pointer stars in Ursa Major indicate the position of Polaris, the North Star, which represents the tip of the tail of the Little Bear, and the end of the handle of the "Little Dipper." In all ages of the world, Ursa Minor has been more universally observed and more carefully noticed than any other constellation, on account of the importance of the North Star.
Polaris is a little more than 1 from the true pole. Its light takes fifty years to reach us.
A line joining Ca.s.siopei, and Megres, in Ursa Major, will pa.s.s through Polaris.
At the distance of the nearest fixed star our sun would shine as a star no brighter than Polaris which is presumably about the sun's size.
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