There is another crater mountain which you should by all means know and that is Copernicus[2] (pronounced Ko-per´-ni-kus). Look through your glass at the southeastern end of the Apennines and you will see a crater that is larger in diameter than Tycho, though it is not so deep. Tycho, Copernicus and the Apennines will serve you well as landmarks if you follow up the explorations of the Moon which you have so well begun. [Footnote 2: Copernicus—Polish, astronomer. Born 1473. Before his time it was believed that the Sun, Moon and stars revolved round the Earth. Copernicus showed that the Earth was a planet and, with the others, that it revolved round the Sun.] =The Sun.=—You can see the spots on the Sun quite well with your glass, and sunspots are always interesting. Do not try to look at the Sun through your glass without covering the eyepiece either with a thickly smoked or dark-colored glass. You must also use smoked or colored glasses over your eyepiece when you are looking at an eclipse of the Sun. You should look for sunspots this year, 1920, for they are decreasing in number and size and in a few years there will be scarcely any. After that there will be more of them again. =The Planets.=—After you have seen the mountains on the Moon and the spots on the Sun you should next turn your glass on the planets. While you will probably say that the planets loom up very small—the largest, Jupiter, appearing about the size of the head of a large pin—yet they are wonderful to look at even through the smallest telescope. =Mercury.=—This is a planet not easy to see even with the aid of a glass so if you see it you can think that you are lucky or skillful or perhaps a little of both. =Venus.=—Venus can be seen very much better with your small glass than Mercury, but you will only be able to see it as a little disk and not as a crescent for your glass is of too low a magnifying power. It is a brilliant object though even through the smallest glass. =Mars.=—While you cannot see the canals of Mars with your glass you can see it as a bright disk of light and this is well worth while. Mars is believed to be peopled and the thought that it may be makes it a mighty interesting object to look at. Look at it through your glass and think it over. =Jupiter.=—On account of his great size you will be able to see Jupiter better than any of the other planets. His disk will show clear and distinct and if you have good eyesight and your glass is fairly good you will be able to see one and perhaps two of his nine moons which will appear as little points of light close to the planet. =Saturn.=—The rings of Saturn cannot be seen with a glass magnifying less than four times. His rings are at this writing (1915) in the best position to be seen as the flat side of the rings is toward us now. In 1921 the edge of his rings will be in a line with the Earth and then it will be very hard to see them even with a much larger telescope.