Beginners’ Guide to Telescopes

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 3.  A telescope needs a ‘mount’ or mounting, to hold it steady and enable you to steer it around the sky.  Make sure any telescope you buy comes complete with the mount and a tripod or stand to which you bolt the mount.   A sturdy, firm tripod or stand is very important to minimise the vibration a telescope will suffer when you touch it to focus or move position.  Avoid flimsy tripods even though they may be lighter and more portable. 

Starter scopes will come complete with a mount in one of three flavours:

 

Altazimuth or ‘alt-az’ mount – this is the simplest up-down, left-right mount, just the same as a pan and tilt photographic camera mount.  They are the easiest to use, don’t need any special set-up, and are probably the most portable, but the hardest to keep the target in view and can become annoying for this reason — the sky appears to be moving continuously and an object will quickly drift out of the small field of view of a telescope, so you need to move the mounting to follow it across the sky and keep it in view.  It’s not possible to fit motors to traditional alt-az mounts but there is now a type of motorised alt-az called an ‘autotrak’ or ‘supatrak’.   A ‘Dobsonian’ or Dob is actually a cheap but effective way of mounting a Newtonian reflector on an alt-az mount.    It can be tricky to follow an object across the sky with a non-motorised alt-az mount or Dob but easier with an ‘equatorial’

 

 

 

Equatorial or EQ mount.   These allow the telescope to be moved ‘left-right’ parallel to the celestial equator, thus following the apparent path of a star or planet more easily.  Control knobs called ‘slow motions’ are fitted which you turn to adjust the mount up-down and left-right.  Equatorials need to be set-up at the correct angle equal to the latitude of your observing location, and with the mount aligned pointing at the celestial pole (ie north in the northern hemisphere).  This isn’t all that difficult to do for casual observing and, once you’ve learned how to set it up, an equatorial mount can be less annoying to use than an alt-az. One ‘but’ — the eye-piece, controls and finder can end up in difficult positions to use as you track across the sky during a session with an EQ mount.  Equatorials can be fitted with small electric motors (integrated on some models) to drive them across the sky and help keep targets in view.  They are preferred if you plan ultimately to do any astro-photography.

 

 

A ‘GO-TO’ mount – the easiest of all to use once you’ve done the set up.  These can be types of alt-az or equatorial mounts driven by battery-powered motors controlled by a tiny on-board computer that has a database of star and planet positions.  You use a hand-held controller to select the target and the telescope moves itself to where it thinks the target is, and then keeps tracking automatically.  Set-up can be tricky but they usually have good instructions and once you’ve mastered it a go-to should be the easiest to use.  They’re also the most pricey (of course).

You can now also buy go-tos with built-in GPS satellite positioning technology (like the sat-nav found in some cars).  These can automatically align themselves north and make set-up a lot easier.  As you might guess, at present they cost more than the starter budget, but you may feel like pushing the boat out one day!

 

As well as the mount and tripod or stand, a starter scope should also include one or two eye-pieces (essential), and a small finder telescope (or red-dot finder) which attaches to the side of the main telescope and is important to help you get the scope pointed at the target.   Most starter scopes come complete with all this stuff but do make sure, otherwise you’ll need to buy the missing bits.

 

Altazimuth Mount

Dobsonian Mount

Equatorial Mounting

GO-TO Mounting

Overview p2 / 4

Overview