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Buying Your First Telescope

By , Saturday 9th November 2013 in How-To Guides

Buying your first telescope can be a daunting task. We show you what you should look for and how to quickly get up and running.

Depending on your previous astronomical experience, you may already have a good idea of what you are after in your first telescope. If you are just starting out, you are probably just as confused as I was when I started.

Don't Buy a Telescope! At least not one of those £20 telescopes that appear in toy shops or around Christmas time. As with everything, you get what you pay for, and in these cases it'll be very disappointing. Read this guide to find out what you want from a telescope, spend the little extra and get one that will last you for years to come.

When you're buying a car you want to know how fast it can go, how big it is and whether it's going to be any good for what you want. Your first telescope is no different, so let's look at some of the specifications you'll need to know.

First off, don't be fooled by claims of massive magnification. That's not the measure of a good telescope. Even poor telescopes can magnify many times. What's really important is the quality of the lenses and the size of the telescope's lens or main mirror (its aperture, measured in millimetres).

The bigger the mirror or lens, the more light can be captured and the brighter a distant celestial object will appear. You'll also encounter the 'f' number, which is the focal ratio of the scope. This tells you what the scope is good for. A lower focal ratio of around f/5 is great for observing large, faint objects like galaxies, while higher focal ratios around f/10 are good for looking at brighter things like the planets. Also, the higher the focal ratio, the narrower the field of view that you see in the eyepiece. So if you want to study small features on the Moon, then a scope with a high focal ratio is for you.

What type of telescope should I buy?

The simple answer is, it depends on what you want to look at in the night sky. Each of the different designs of telescope have their advantages and disadvantages. You have to weigh up each one and decide on the overall best telescope for you. Many astronomers have more than one telescope, but to start off with, I believe its best to invest in one good quality telescope, than two lesser quality telescopes.

Newtonian Telescopes

Newtonian Telescope
Newtonian Telescope
A good all-round beginner's telescope is the Newtonian reflector. These reflecting telescopes were invented by Sir Isaac Newton, and use a specially curved main mirror to collect celestial light. The light gathered by the large primary mirror is focussed and aimed at a smaller secondary mirror, which in turn focuses the light into the eyepiece. It's a simple design and is relatively cheap for the size of mirror you'll get for your money - ideal if you're just starting out. A Newtonian reflector with a 6 inch (150mm) mirror will give you good views of the brighter galaxies and nebulae, and should also perform well when looking at the Moon and planets.

 

Refractor Telescopes

Refractor Telescope
Refractor Telescope
A refractor the oldest and perhaps the most recognisable of all designs. The refractor telescope was type used by Galileo to record the phases of Venus among other things. Refractors have a curved lens at the front, which focuses the light down the tube directly into the focuser. A star diagonal is often added between the focuser and eyepiece to make viewing more comfortable. Refractors are great for observing the Moon, planets or rich star clusters.

 

Dobsonian Telescope

Dobsonian Telescope
Dobsonian Telescope
The Dobsonian telescope is another type of reflecting telescope, but mounted on a simple altazimuth mount popularised by amateur astronomer John Dobson in the 1960s. If you want to chase faint galaxies and nebulae, this type of telescope has a much larger mirror for its price compared to any other design because it has a simple mount, however you can't track objects across the sky.

 

Catadioptric Telescopes

Catadioptric Telescope
Catadioptric Telescope
Finally, there are the catadioptric telescopes, or compound telescopes, which use a combination of corrector lenses and mirrors. Their compact size makes them relatively portable and their large focal ratios mean that they're ideal for lunar and planetary observing. Popular designs include the Schmidt-Cassegrain and Maksutov-Cassegrain.

 

What is the mount?

The mount is the most important part of the telescope. A telescope with superb optics will always be let down by a poor-quality mount. If you can't keep the optics stable, your view of the night sky will be completely ruined, so make sure that the mount is sturdy. The heavier the mount the better, because it will be a solid platform for the telescope, but you have to weigh up the benefits of a heavier mount with portability and ease of setting it up - its weight has obviously got to be offset by how portable you want your telescope to be. It shouldn't have any flimsy plastic parts and under no circumstances should it flex or wobble noticeably when set up.

There are two main types of mount that you'll come across: the altazimuth (alt-az) and the equatorial (eq). Altazimuth and Alt-az stand for altitude and azimuth and is the simplest of all mounts. The telescope moves on a base parallel to the ground up and down (in altitude) and left and right (in azimuth).

The equatorial mount (typically the German equatorial mount, or GEM) is different; one of its axes is tilted to your latitude and the other is parallel to the celestial equator. It moves in units of Right Ascension and Declination, which are similar to longitude and latitude and mapped onto an imaginary sphere on the sky. Most Newtonians come on a German equatorial mount.

Is it worth considering a computerised Go-To Mount?

Go-To telescopes come with an inbuilt computer and handset that, provided they are set up correctly, automatically aims the telescope and tracks an object. Although this is helpful, i'd recommend that you opt for a mount without Go-To as your first-time buy. If you aren't familiar with using a telescope, setting up a scope without Go-To is much easier. A non-Go-To is also much cheaper and will be a gentler introduction to how telescopes work as well as helping you to get to know the nights sky.

From personal experience, my Go-To mount has proven invaluable in light polluted areas which cause deep sky objects to be near impossible to see, but long exposures with a camera can pick them up. The Go-To mount makes finding these objects much easier, often within 30 seconds, opposed to an hour of star hopping and trial and error with the camera.

How much should I spend on my first telescope?

A good Newtonian on a sturdy mount costs around £200 in the UK, while a good refractor costs around £300. A 6-inch Dobsonian can cost as little as £155.

What's most important is that you buy from a reputable astronomical dealer, or a major retainer, and above all avoid the cheap, poor-quality models you sometimes see in mail order catalogues or high street stores.

The best brands to buy include SkyWatcher and Celestron at the lower end of the market, Orion and Meade are towards the higher end with Takahashi generally regarded as being among the best. Personally I have two SkyWatcher telescopes and have been very pleased with them. I've used Celestron and they are very similar to SkyWatcher.

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About the Author

Tim Trott

Tim is a professional software engineer, designer, photographer and astronomer from the United Kingdom. You can follow him on Twitter to get the latest updates.

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One thought on “Buying Your First Telescope”
  1. Gravatar
    Gary Sonnenberg

    Hi Tim,

    Thanks for the overview, but it seems to me that you're talking about a lot of advanced features here. Isn't there something more basic for the beginner to look at?

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