HOW TELESCOPES WORK

Optical telescope use lenses or minors to make distant objects look bigger and brighter. Lens telescopes are also called refractors. Mirror telescopes are called reflectors. Most large astronomical telescopes for looking at stars are reflectors.

The first experiment shows you how to make a reflecting telescope’s main mirror is curved, so that light rays bounce off at an angle. The refracting telescope in the second experiment uses lenses. There are difficulties involved in making big lenses, which is why most of the telescopes used in astronomy are reflectors. Our brains work out how big an object is by analyzing the angle of the light rays from it as the rays enter our eyes. Telescopes use lenses or minors to change this angle. Bending light rays from distant objects makes them seem larger than they would appear to the naked eye.

YOU WILL NEED

• Make a single-mirror reflecting telescope:
  Desk lamp, thick purple paper, marker pen, scissors, tape, small mirror, nonhardening modeling material, magnifying glass.
  
  
• Make a refracting telescope:
  Desk lamp, thick red paper, marker pen, scissors, tape, two magnifying glasses, nonhardening modeling material.

STEP 1
Draw a circle around the font of the desk lamp on a sheet of purple paper. Cut it out. Then cut out an arrow in the middle. Stick the circle onto the front of the lamp.

STEP 2
Set up the desk lamp and mirror so that the mirror reflects the light from the lamp onto a nearby wall. Use modeling material to help support the mirror, if necessary.

STEP 3
Set up the magnifying glass, so that light reflecting from the mirror passes through it. The lens magnifies and focuses the light, projecting an upside-down arrow.

STEP 1
Draw around the front of the desk lamp on a sheet of red paper. Using scissors cut out a star in the middle of the circle. Then cut out the circle, as shown.

STEP 2
Using tape, fasten the circle of paper securely over the front of the desk lamp. Make sure that it does not touch the bulb, because this could cause the paper to burn.

STEP 3
Position the desk lamp so that it shines on a nearby wall. Adjust the angle of the lamp if necessary. Make sure that the lamp’s base is stable, to prevent it from tipping over.

STEP 4
Position a magnifying glass between the lamp and the wall. To support the glass and fix it in place, take the handle and wedge it firmly in a lump of modeling material.

STEP 5
Turn on the lamp. Adjust the magnifying glass, so that the light passing through it appears as a blurred patch of light on the wall. The glass acts like a telescope’s objective lens.

STEP 6
Position the second lens behind the first lens. This acts as an eyepiece lens. Adjust the eyepiece lens, until the light is focused to form the sharp image of the star.