--------+---------+---------+---------+---------+---------+--------- Day of | July | August |September| October |November |December Month | | | | | | --------+---------+---------+---------+---------+---------+--------- |_m_ _s_ |_m_ _s_ |_m_ _s_ |_m_ _s_ |_m_ _s_ |_m_ _s_ 1 |S 3 28 |S 6 10 |S 0 6 |F 10 8 |F 16 18 |F 11 3 6 |S 4 24 |S 5 46 |F 1 31 |F 11 41 |F 16 17 |F 9 3 11 |S 5 11 |S 5 8 |F 3 13 |F 13 4 |F 15 56 |F 6 51 16 |S 5 46 |S 4 15 |F 4 58 |F 14 16 |F 15 13 |F 4 30 21 |S 6 9 |S 3 9 |F 6 45 |F 15 13 |F 14 10 |F 2 2 26 |S 6 11 |S 1 51 |F 8 29 |F 15 54 |F 12 45 |S 0 28 31 |S 6 12 |S 0 24 |F 10 8 |F 16 16 |F 11 3 |S 2 55 --------+---------+---------+---------+---------+---------+--------- As we have seen in Chapter X every day of the year is exactly 24 hours long by our clock time. The time by the Sun is usually either ahead or behind local clock time. The difference between clock time and Sun time is called the _equation of time_, and a table to show how many minutes and seconds the Sun is fast or slow, according to clock time, is given above, taken from “The New Astronomy,” by Professor Todd, who has kindly permitted me to use it here. In the table =S= means that the Sun is slow, that is, that the Sun does not cross the meridian until after the clock shows noon, and =F= means that the Sun is fast, that is, that the Sun has crossed the meridian before the clock shows noon. =m= means minutes, and =s= means seconds above the figures. The table gives the average values of the equation of time, which may differ by a few seconds from the values for any particular year. APPENDIX M THE KULLMER STAR FINDER The star finder shown in the picture was invented by Dr. C. J. Kullmer, of Syracuse, N. Y., and has been highly praised by many great astronomers. [Illustration: FIG. 186.—KULLMER STAR FINDER.] You should own one if possible, for you do not need to know anything about the stars to operate it. It is mounted on the principle of a big telescope, but it is a naked eye instrument, an arrow taking the place of the telescope. The finder is placed on a table, or other level surface, with the dial facing north. Then the pointer and dial are set for the day and hour when you want to find the position in the sky of a certain constellation. The indicator is turned to the name of the constellation on the dial, and this also tells the direction to set the arrow. This is all there is to it and the arrow points right at the group of stars you want, whether they are above the horizon or not.