Note well, also, these particulars about the charts:  Chart No. 1 includes the first four hours of right ascension, from 0 h. to 4 h. inclusive; Chart No. 2 includes 4 h. to 8 h.; Chart No. 3, 8 h. to 12 h.; Chart No. 4, 12 h. to 16 h.; Chart No. 5, 16 h. to 20 h.; and Chart No. 6, 20 h. to 24 h., which completes the circuit.  In the first three charts the line of 0 deg., or the equator, is found near the bottom, and in the last three near the top.  This is a matter of convenience in arrangement, based upon the fact that the ecliptic, which, and not the equator, marks the center of the zodiac, indicates the position of the tracks of the planets among the stars; and the ecliptic, being inclined 23 deg. to the plane of the equator, lies half to the north and half to the south of the latter.

Those who, after all, may not care to consult the ephemeris in order to find the planets, may be able to locate them, simply from a knowledge of their situation among the constellations.  Some ordinary almanacs tell in what constellations the principal planets are to be found at various times of the year.  Having once found them in this way, it is comparatively easy to keep track of them thereafter through a general knowledge of their movements.  Jupiter, for instance, requiring a period of nearly twelve years to make a single journey around the sun, moves about 30 deg. eastward among the stars every year.  The zodiacal constellations are roughly about 30 deg. in length, and as Jupiter was in Sagittarius in 1901, he will be in Capricornus in 1902.  Saturn, requiring nearly thirty years for a revolution around the sun, moves only between 12 deg. and 13 deg. eastward every year, and, being in conjunction with Jupiter in Sagittarius in 1901, does not get beyond the border of that constellation in 1902.

Jupiter having been in opposition to the sun June 30, 1901, will be similarly placed early in August, 1902, the time from one opposition of Jupiter to the next being 399 days.

Saturn passes from one opposition to the next in 378 days, so that having been in that position July 5, 1901, it reaches it again about July 18, 1902.

Mars requires about 687 days to complete a revolution, and comes into conjunction with the earth, or opposition to the sun—­the best position for observation—­on the average once every 780 days.  Mars was in opposition near the end of February, 1901, and some of its future oppositions will be in March, 1903; May, 1905; July, 1907; and September, 1909.  The oppositions of 1907 and 1909 will be unusually favorable ones, for they will occur when the planet is comparatively near the earth.  When a planet is in opposition to the sun it is on the meridian, the north and south line, at midnight.

Mercury and Venus being nearer the sun than the earth is, can never be seen very far from the place of the sun itself.  Venus recedes much farther from the solar orb than Mercury does, but both are visible only in the sunset or the sunrise sky.  All almanacs tell at what times these planets play their respective roles as morning or as evening stars.  In the case of Mercury about 116 days on the average elapse between its reappearances; in the case of Venus, about 584 days.  The latter, for instance, having become an evening star at the end of April, 1901, will become an evening star again in December, 1902.