Go Out:  Look Up!

A Guide to the Sky, Telescopes, and Telescope Programs

Home How a Scope Works Using a Scope Note to Parents Aiming a Scope Using a Finder Eyepieces Using a Zoom Fun Equipment

How Reflectors Work
How SCT's Work

How a Telescope Works


  • Gather More Light - See Fainter Objects
  • Magnify Objects

How a Scope Gathers More Light

Let's start with the eyes.

In the dark, the eye's pupil widens to let more light in.  About 10 times more light  can enter the eye when the pupil is fully-dilated compared to when it is most narrow.

One purpose of a telescope is to get more light into the eye.


Refracting Telescopes

Glass can bend light.  A lens is specially shaped to bend light to a point - like an eye.  A six-inch lens can bend the equivalent of 576 eyeballs worth of light into your eyeball.

This is the essence of what all telescopes do. 

The schematic above shows how a refractor works.  Curved mirrors can be also be used to get more light into your eye and are detailed on the next page.

Next: How Reflectors Work



Questions or comments? Email:Jeff Martin