The night sky
Anyone with a keen interest in astronomy may want to acquire their own telescope. There is a large range of good telescopes on sale in most countries, with Europe and North America being particularly well supplied. The amateur astronomer can use a great variety of instruments and techniques, and even build an observatory to professional standards given the money and enthusiasm. In this section our aim is to answer a few of the basic questions on choosing and using an instrument.
The first thing to do before buying any instrument at all is to find your way around the night sky. It is not at all difficult to pick out a few of the brighter constellations and memorize them. The star charts in this book will enable you to recognize the more prominent patterns, and eventually the fainter constellations. If you live in the northern hemisphere learn to recognize Ursa Major (part of which is called the Big Dipper or the Plough), Cassiopeia, Ursa Minor, Cygnus, and Auriga. Southern observers have the glorious constellation Carina, as well as Crux Australis (the Southern Cross), Centaurus, and Scorpius. Orion, the splendid group on the equator, is visible in both hemispheres. Owing to Earth rotation and motion round the Sun, the night sky changes from hour to hour and season to season, so you cannot see all the constellations at one time. It is also useful to remember the names of some of the brighter stars, such as A returns. Sinus, Canopus, Betelgeuse and Vega. By identifying one or two constellations and stars each clear night you will soon become familiar with a great many of them; and they become mueh more interesting once you know where to find them all! A useful aid to elementary star recognition is a small map, not more than 25em in size, that can be used easily outside. A torch covered with red paper can be used to examine the map in the dark; without any filter most torches are so bright as to affect the adaptation of the human eye to the darkness of the night sky.
Once the main features of the night sky are well known, it is time to think about an instrument. It is important to appreciate that the very cheapest telescopes are little more than toys and are no good for amateur astronomy. True, they will show the Moon’s craters, Jupiter’s moons, and the crescent of Venus, after a fashion, but not much more. The cheapest instrument that the amateur astronomer should consider buying is a good pair of binoculars. As these are produced in much greater numbers than astronomical telescopes, economies of scale govern the production costs. Consequently a modest sum of money spent on good binoculars is much better value than a telescope at a similar price.