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.
With the aid of the Nautical Almanac and the charts the amateur will find no difficulty, after a little practise, in keeping track of any of the planets.
In the back part of the Nautical Almanac will be found two pages headed "Phenomena: Planetary Configurations." With the aid of these the student can determine the position of the planets with respect to the sun and the moon, and with respect to one another.

The meaning of the various symbols used in the tables will be found explained on a page facing the calendar at the beginning of the book.

From these tables, among other things, the times of greatest elongation from the sun of the planets Mercury and Venus can be found.
It may be added that only bright stars, and stars easily seen, are included in the charts, and there will be no danger of mistaking any of these stars for a planet, if the observer first carefully learns to recognize their configurations.