Galileo pioneered modern explorations in the early 1600's by using a device originally invented for naval operations to explore the heavens. The device he used, of course, was the telescope , an instrument used to gather and focus light. Our atmosphere prevents most of the electromagnetic radiation from reaching the ground, allowing just the visible band, parts of the radio band, and small fractions of the infrared and ultraviolet through. The development of space technology has enabled astronomers to put telescopes above the atmosphere and explore all of those places out there using the full range of the electromagnetic spectrum. This chapter covers the basics of telescopes and the effects of the atmosphere on images.
Vocabulary terms are in boldface .
There are two basic types of telescopes, refractors and reflectors. The part of the telescope that gathers the light, called the objective , determines the type of telescope. A refractor telescope uses a glass lens as its objective. A reflector telescope uses a mirror as its objective. The refractor telescope uses a lens to gather and focus light.