Refractors: The 'traditional' type of telescope with a 'big' lens at one end and a small lens, the eyepiece, at the other. However, most reputable makes also include a diagonal ( mirror or prism) which diverts the light at right angles into the eyepiece. Saves you having to lie on your back when looking at something overhead.
Reflectors: A typical reflector would be a Newtonian or Dobsonian. These use a 'big' mirror to gather the light at the bottom of the telescope which is then reflected back to a small mirror at the top of the tube which reflects the light at right angles out of the side of the tube into the eyepiece.
Catadioptrics: These are telescopes which use a combination of mirrors and lens. The main mirror collects the light and reflects that back to another small mirror or lens which is itself 'attached' to a collector plate. This mirror or lens then reflects the light back through the main mirror on to another mirror (diagonal) which reflects the light at right angles into the eyepiece. This arrangement results in a much shorter tube length for any given aperture. The most common type are the SCT's (Schmidt- Cassegrain) followed by the
Maksutov-Cassegrain and other variations.
Thanks to Brian Cox and Stargazing Live there has been a big surge in interest in astronomy. And the manufacturers haven't been slow to take advantage of this. One result has been big increase in the bottom end of the market of small, cheap scopes for £100 or less. Disregarding these for the moment let us look at the Skywatcher SynScan GOTO telescopes. This range includes Refractors, Reflectors and Catadioptrics and range in size (aperture) from 70mm up to 130mm. Celestron, Meade, Orion and Bresser have similar ranges.
How much? From about £200 to just under £400. All of these scopes will show you the Moon, the planets and some of the more obvious, interesting objects in the sky. And with the larger aperture ones you will start to be able to see the fainter deep sky objects, split more double stars, etc. , always assuming that the viewing conditions are good and there isn't too much light pollution.
But the smallest only has a 70mm (2.75 in) lens, so that no matter how many objects you choose from their databases - some will claim 40,000 or more objects - most of them will be invisible.
For around £250 or so you can get a 114mm (4.5 in) Celestron 114LCM catadioptric Newtonian. The Swansea Astronomical Society purchased one for use at Star Parties and as a recommended entry level telescope for beginners. It is a computerised GOTO telescope (see later) but you will need a power tank to go with it, which brings up the cost to around £300.
The slightly larger 127mm Maksutov-Cassegrain Telescope costs around £400.
Many of these are excellent for what astronomers call Grab-and-Go Scopes. This covers situations where you haven't the time or energy to spend a lot of effort setting the scope up, or for travel on holidays or to the local Star Party, and so on.
Please note that all prices quoted are approximate, subject to change
and for guidance only
102mm Refractor - StarTravel SynScan GOTO
130mm Reflector - Skywatcher Explorer SynScan GOTO