How Telescopes Works

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The introduction to how telescopes work

Maybe you've been out looking at the stars in the night sky, searching for constellations; or maybe you've already learned your way around the constellations, and now you'd like to take a closer look -- at ­objects like the moon, planets or stars -- with the aid of a telescope.


How they work 


A telescope is an amazing device that has the ability­ to make faraway objects appear much closer. Telescopes­ come in all shapes and sizes, from a little plastic tube you buy at a toy store for $2, to the Hubble Space Telescope, which weighs several tons. Amateur telescopes fit somewhere in between, and even though they are not nearly as powerful as the Hubble, they can do some incredible things. For example, a small 6-inch (15 centimeter) scope lets you read the writing on a dime from 150 feet (55 meters) away!

If you had a "bigger eye," you could collect more light from the object and create a brighter image, and then you could magnify part of that image

The objective lens (in refractors) or primary mirror (in reflectors) collects lots of light from a distant object and brings that light, or image, to a point or focus.


Telescope Mounts

Telescopes must be supported by some type of stand, or mount --

otherwise you would have to hold it all of the time. The telescope mount allows you to:

keep the telescope steady

point the telescope at the stars or other objects (birds)

adjust the telescope for the movement of the stars caused by the Earth's rotation

free your hands for other activities (focusing, changing eyepieces, note-taking, drawing)

There are two basic types of telescope mounts: Alt-azimuth
Equatorial