Beginners’ Guide to Telescopes

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Choices:  Types of Telescope & Mount


Use lenses — typical aperture (lens diameter) on such a starter scope is from 60mm to 120mm


Use mirrors — most common type is the ‘Newt’ (Newtonian—pictured) where the eye-piece is at the top (front) of the scope.  Typical aperture (mirror diameter) on such a starter scope is from 114mm to 150mm

Maksutov or ‘Mak’ (catadioptrics)

Use both mirrors and lens (corrector plate) in combination in a sealed tube.  Most common types are the ‘Mak’ (Maksutov-Cassegrain —pictured) and the Schmidt-Cassegrain ‘SCT’ which both use the Cassegrain mirror system where the eye-piece is at the bottom (back) of the scope.  Typical aperture (mirror diameter) on such a starter scope is from 80mm to 127mm

Altazimuth Mounts

Most intuitive to use — allow movement up-down (altitude), and left-right (azimuth).  Also convenient for terrestrial use (eg bird-watching).  Movement is needed in both axes (altitude & azimuth) to track a star or planet. Can now be bought in motorised ‘autotrak’ versions.

Equatorial Mounts (EQ)

Less intuitive to use than the alt-az but more convenient to track planets and stars.  They mount the scope parallel to the Earth’s axis of rotation and allow movement left-right, parallel to the celestial equator (R.A. or right ascension) and up-down, across it (Dec. or declination).  Only movement in one axis (the R.A.) is mostly needed for tracking, and this can be done by fitting a motor drive.  Need to be set-up with the polar axis pointing at the celestial pole.

GO-TOs and GPS/auto-aligns

use computer control to drive a motorized alt-az or fork mounting automatically, to find the particular star, planet, or deep-sky object selected in the hand-held control panel.  The latest GPS auto-align systems will perform automatic set-up and polar alignment.  Simpler ‘Go-to’ systems require an alignment procedure during set-up.

Tripod stand

Used on almost all typical starter scopes.  Easy to erect, but look for a robust, firm tripod that won’t shake and won’t break

Pillar Stand

seen on some scopes.  Look for a stable, robust stand that won’t shake or break

Types of Telescope

Types of Mount

Dobsonian or ‘Dob’

A very cost-effective way of mounting a Newtonian reflector on a simple type of alt-az mount.   Offers more aperture (light-gathering power) for your money.  You can now also buy Dobs on mounts wired with a hand controller read-out to guide you to selected targets — called ‘push-tos’

What are my choices?  What different kinds of small telescope are there?