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TELESCOPES

6

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A CLOSER LOOK AT REFLECTORS

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NEWTONIAN REFLECTORS

The greatest advantage to Newtonian reflectors is their cost per millimeter of aperture (size). Another great advantage is the ability to put the large ones

onto a simple and inexpensive mount like the Dobsonian

mounts.

It is more important to place a refracting telescope onto a equatorial mount

(dimensions).

The long focal lengths

because of their long focal lengths

give the refractor a narrow field of view which needs more tracking assistance from the mount than a reflector. The reflector generally comes in shorter focal lengths which have wide fields of view. So what I'm saying is the money you spend on a refractor with an equatorial mount can be used to buy a reflector on a Dobsonian mount which will give you a telescope three

TELESCOPE LINKS:

Basics

Mounts

Light Gathering Power

times the size for same money.

This means awesome

light gathering power.

Closer Look At Refractors

Dimensions

A reflector's mirror is a lot simpler and cheaper to make (do one at home if

Balancing

you wish through

BYOT - Build Your Own Telescope)

than the specialised,

Eyepieces

highly accurate figuring of high quality glass to make an achromatic lens.

The mirror of a reflecting telescope is completely free from chromatic abberation, unlike the refracting telescope. However the eyepieces used to magnify the image are of the refracting type so there could be some abberation if cheaper eyepieces are used.

Cleaning

Tips

Astrophotography

Build your own telescope

Build your own telescope
for schools

Binoculars

A frequently asked question about reflectors is, can they be used during the day? The answer is yes! Reflecting telescopes provide wide field , bright and clear pictures during the day, but the image is upside down and the other way around (back to front). This could quite annoy some people, but the people who use them during the day and myself discover we look at the picture for what it is and not be bothered if it's backwards or upside down.

Reflecting telescope mirrors which gather the light are just a parabola curved surface with with a coating of aluminium placed on it. It's this aluminium coating that does all the work of gathering the light, whereas the shaped glass is only there to support it. Telescope mirrors can be made out of anything hard really, and have the aluminium coating put on them, but glass is easy to grind and polish to a accurately flat surface. Also glass has fairly low expansion rate so it will not warp much when placed into a different temperature like taking the telescope from inside a warm house to outside in the cold. Other materials can be used for making the reflective mirror, but are more expensive and harder to grind, especially at home. eg. Pyrex or fused silica.

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