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Telescopes open up the night sky; WITH DAVID WARRINGTON Stargazing.

Byline: DAVID WARRINGTON

THE human eye, while a fantastic sensory organ, is not always great for looking at the night sky.

So we often need a bit of optical help when viewing the universe.

Our eyeball only has a small opening at the front, an aperture which doesn't let too much light in. This limits what we can see, since a lot of objects in the night sky are very faint and distant.

The magnification our eyes provide is also fixed and moving closer to the stars isn't a realistic option.

The telescope was designed to overcome both of these limitations.

Optical telescopes, when pointed at distant objects, make things appear closer, larger or brighter to our eyes.

Telescopes have larger apertures than the human eye, allowing us to collect more light from distant objects. This is why telescopes are often referred to as "light buckets".

The bigger the telescope, the more light can be collected and so you're able to view images with much greater clarity.

Telescopes and eyepieces also magnify the image of an object. However, magnification is not something astronomers tend to consider all the time.

Apart from relatively nearby objects in the solar system, most objects in space are so far away that no amount of magnification makes a difference - a star still looks like a point of light in a telescope.

So how do optical telescopes work? They can generally be broken down into two categories - refractors and reflectors.

The refracting telescope uses two lenses and was first invented in 1608 in the Netherlands.

Light passing through the first lens is refracted (the light rays are bent) before being focussed by the second eyepiece lens.

The distance and type of the two lenses, placed at either end of a tube, can be varied to produce different resolutions and magnifications.

Several decades later, scientists started to experiment with the properties of mirrors and the reflecting telescope was introduced toward the end of the 1600s.

A reflector produces an image by collecting light from an object on a curved mirror. This directs the light rays to a second mirror which reflects toward the observer's eye.

The Newtonian reflector, named after its inventor Isaac Newton, was first built around 1670 and is a common type still used today.

Before this, the far less well-known Scots astronomer and mathematician James Gregory designed a reflecting telescope which is now known as a Gregorian telescope.

And 400 years on, many people can affordably own telescopes themselves.

For a budget of under PS300 you can purchase a range of very capable telescopes for occasional use in your back garden and view the Moon and planets in some detail.

| David Warrington, FRAS, is resident astronomer at the Scottish Dark Sky Observatory in Dalmellington, Ayrshire. Find out more at www.scottishdarkskyobservatory.co.uk.

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MOON SHOT A telescope will let you see the Moon in detail

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Title Annotation:Letters
Publication:Daily Record (Glasgow, Scotland)
Date:Jun 11, 2016
Words:483
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