Collecting Light and Making Images Sharper
Introduction
Telescopes collect light from distant objects. They collect more light than a human eye can and make objects look brighter and sharper.
When a lens is used to collect the light, the telescope is called a refractor. When a mirror is used, it is called a reflector.
Refractors
The light enters the larger objective lens, which bends the light to a focal point. The secondary lens redirects the light to the eye or a camera (first image). The Newall Telescope is a 9 metre long refractor (second image).
A simple refracting telescope uses lenses to help us see faraway objects. Credit: NASA/JPL-Caltech
Reflectors
The light is collected and focused by the primary mirror. A series of further mirrors are used in different telescopes to redirect the light to scientific instruments or the eye.
The Herschel Reflecting Telescope was designed by William Herschel, who discovered the planet Uranus.
A simple reflecting telescope uses mirrors to help us see faraway objects. Credit: NASA/JPL-Caltech
Basic Instructions for Visitors
This interactive station has three separate sections to experiment with. One is situated on the end of the right hand side of the table, and you will need to be stood around the right-hand end of the table to interactive with it. This is Station 1. Then, the other two (Station 2 and 3) are side-by-side along the front of the table. They are both inside a metal-framed box. Station 2 is the one on the right and Station 3 is the one on the left.
WARNING: never look directly into laser beams, risk of eye damage.
Station 1 - Look through a refracting telescope
Look through the smaller lens towards the larger lens.
What can you see by looking through both of these lenses at the same time?
Move both lenses along the track until the view looks clear and focussed.
Station 2 - Light through a refractor
Move the small lens and large lens along the track. Do not attempt to move anything else.
Get the three laser beams to cross in the middle of the red block.
Make small adjustments until the three lasers are centred on the target on the screen.
Station 3 - Light through a reflector
Move the circular mirror along the track. You can also rotate the circular mirror with the handle. Do not attempt to move anything else.
Get the three laser beams to cross in the middle of the red block.
Make small adjustments until the three lasers are centred on the target on the screen.
Detailed Instructions for Visitors
This interactive station has three separate sections to experiment with. One is situated on the end of the right hand side of the table, and you will need to be stood around the right-hand end of the table to interactive with it. This is Station 1. Then, the other two (Station 2 and 3) are side-by-side along the front of the table. They are both inside a metal-framed box. Station 2 is the one on the right and Station 3 is the one on the left.
Station 1 - Located on right edge of table.
There is a metal track running along the table. On this track are two poles with lenses attached to the top of them. These poles can be moved along the track. Visitors are asked to look through both lenses, with their eye closest to the lens at the edge of table. Looking through these lenses there is a space picture in the distance. The lenses need to be moved along the track to get the image into focus.
Station 2 - Right hand side box.
This interactive demonstrates how the light travels through a basic refracting telescope. A refracting telescope uses lenses, like the model for Station 1. On the right hand-side of this box is a tray with some pieces of paper. These contain tactile diagrams to help demonstrate the light as it travels through the telescope models demonstrated in Station 2 and Station 3. You can pull these out and feel the raised lines on the diagrams. Please place them back when you have finished.
You can carefully put your hand inside the box along the bottom, underneath the plastic screen. You can feel four poles. The first pole, on the left, holds three lasers at the top and can not be moved. The second pole from the left holds a lens on the top and can be moved along the track. The third pole holds a red resin box and can not be moved. The final pole holds a second lense and can be moved.
The idea of this station is to watch how the lenses re-direct the laser beams. The three lasers beams start parallel to each other and pass through the first lens. They then converge (come together) in between the two lenses. This can be seen inside the red resin block then the lenses are in the correct position. After this convergence point, the laser beams diverge (come apart) before the second lens. After the second lens the laser beams are parallel again. This demonstrates how light is focussed by a refracting telescope.
Station 3 - Left hand side box.
This interactive demonstrates how the light travels through a basic reflecting telescope. A reflecting telescope uses mirrors. There are many different designs and this is just one example.
You can carefully put your hand inside the box along the bottom, underneath the plastic screen. There are five fixed square-shaped poles inside this box that do not move. There is one cylindrical pole which can be moved along the track and also rotated. This pole contains a concave mirror (curved in) which is what focuses the light in this telescope model. It does the same job as the larger lens in the refracting telescope model.
In this model the parallel laser beams start on the left, bounce off the mirror and start to converge (come together). This can be seen in a red resin box on top of one of the square pole. The laser beams then diverge (come apart) bounce off a flat mirror, before finally going through a small lens.