Astronomy

* The electromagnetic spectrum is the range of wavelengths and frequencies of electromagnetic radiation, including gamma rays rays, ultraviolet rays, visible light, infrared, microwaves and radio waves. Telescopes use optical components to observe light from near infrared to near ultraviolet wavelengths.

* The two basic types of telescopes are reflectors and refractors. Reflectors use a mirror tom form an image whilst refractors use lens. Also, there are Schmidt types which are a combination of both. Large telescopes work on the concept of reflection since the use of large lenses produce a distorted image .Also, when light is bent different colours might be seen on the image.

* The most important powers of a telescope are light gathering power and magnifying power.

* Light gathering power is a measure of how bright an image will be in the telescope, and is determined by the diameter of the objective lens or mirror. Large light gathering power is required to make dim objects detectable. The limits are higher cost for larger telescopes and greater engineering difficulties in making precise instruments larger Magnifying power determines how large the image will appear in the telescope. It is useful in examining the fine details of resolved objects. Unfortunately, turbulence in our atmosphere sets a limit on useful magnifications for ground-based observations.

* Many wavelengths of light do penetrate through the atmosphere at all. The only way to observe them is from above the atmosphere. Even visible light, which does penetrate the atmosphere, is blurred by its passage through the atmosphere. Much sharper images can be obtained from orbit. Some light is absorbed at any wavelength, so images in space are always brighter than those seen on the ground.

* Light gather power defines how much light is gathered by the telescope, and therefore, how bright an object will appear in the telescope. This is important to astronomers because greater light...