Choosing Your First Telescope
Thursday, 11 May 2017 | Neil Parker
Choosing Your First Telescope
If you have never had a telescope of your own you can be forgiven for finding the range of choice bewildering. However, with a little help you will soon find that the choices are easy to understand and that you don't need to be an expert to get a lot of enjoyment from a telescope.
Telescopes for Astronomy
If your primary interest is to look at the night sky then the best option is to choose a telescope designed specifically for astronomy. This will offer better value for money and better performance than a terrestrial telescope. If your main use is for bird-watching or other terrestrial interests then you should consider a field scope. These can also be used for astronomy within certain limitations.
The three most important criteria for a good astronomical telescope are its light-gathering power, the quality of its optics and the mounting. In addition you will want to consider portability, where you will keep and use the telescope, and, of course, the price.
With a few exceptions, all the objects you will want to observe in the sky will be very faint so the ability of the telescope to collect as much light as possible is important. This is the reason why astronomical telescopes tend to be bigger and bulkier than their terrestrial counterparts. Telescopes can be divided into three main types depending on how they collect and focus the light. The first type use a lens and are called refractors; the second type use a mirror and are called reflectors; the third type use a combination of mirrors and lenses and are called catadioptrics. Each type has its own advantages and disadvantages but all types can be used for general astronomy.
Reflectors generally provide the greatest light-gathering power for a given amount of money and are often the preferred choice when viewing faint deep-space objects such as galaxies and nebulae (dust clouds). Refractors are often preferred for planetary observation where good contrast and the ability to show fine details are more important than light-gathering power. Catadioptrics are often the most compact telescopes and are becoming increasingly popular, especially with built-in computer control.
This is perhaps the hardest factor for a beginner to assess, but it is extremely important. In general terms, the more you pay the better the optics are likely to be, but this is only true when buying quality brands from specialist retailers. More expensive telescopes tend to be purchased by experienced users who know how to assess quality so there is little opportunity for poor quality products to make an impact in the higher price ranges. Unfortunately, in the lower price ranges where most people start, there are lots of poor quality products around. These often attract first-time buyers because they are widely available. This is a pity because the disappointing results can put people off for good.
Many of the poorer quality telescopes are sold through department stores, catalogue shops and other non-specialist retailers. These telescopes offer the retailer better profit margins than the quality brands, and this can only be achieved by higher prices or cheaper-quality products.
So how do you ensure you will get the quality of optics you need? The best way is to discuss your requirements with a reputable supplier. His or her aim should be to help you choose the telescope that is best for you within your budget. If you don't feel you are getting good advice, or aren't confident that the sales assistant knows the subject well, then try somewhere else. You can also get good advice from your local astronomy club. These are generally friendly places where people are only too happy to discuss the merits of different makes and models. Try to talk to several people and avoid taking the advice of someone who thinks the only good telescope is the one that he or she owns. It may not be the right one for you.
Telescope mounts come in many different forms but can be grouped into two main types, alt-azimuth and equatorial. Both have two axes to rotate the telescope around. In an alt-azimuth mount the main axis is vertical but in an equatorial mount the main axis is tilted over to be parallel to the Earth's axis of rotation. Alt-azimuth mounts are simpler and cheaper; equatorial mounts are easier to use for tracking objects. (But see the section on Computer Control)
If your interest is very casual and you only want to look at the Moon and perhaps see the Galilean moons around Jupiter and Saturn's rings, then you may want to consider a very simple and inexpensive telescope on a light-weight alt-azimuth mount.
For more serious use an equatorial mount is much easier to use, although at first sight it looks more complicated. These mounts are often fitted with slow-motion controls which are very convenient for making small adjustments, particularly at high magnifications.
One type of alt-azimuth mount deserves a special mention. This is the Dobsonian mount which has become very popular in recent years, particularly for home-built telescopes. It is designed to be used with reflecting telescopes and is very cost-effective for larger ones. Many home-builders are happy to swap ease of use for its low cost.
As we mentioned above, astronomical telescopes can be big and bulky so you need to consider where you will keep yours and how easy it will be to get it out. Remember the old maxim that 'a small telescope outdoors collects more light than a big one in the cupboard". This is one area where the catadioptrics provide an advantage. Their combination of mirrors and lenses tends to produce more compact packages that are easier to handle.
The best way to assess whether a telescope will be manageable is to see it for yourself and feel the weight. This is where a specialist retailer with a good selection of different telescopes can provide invaluable assistance.
If you plan to have a permanent installation you will be able to cope with a larger telescope, but if, like most people, you will need to get the telescope out when you want to use it, make sure you can handle it safely and comfortably, preferably by yourself. If it requires two people to handle the telescope you will find that it doesn't get used as often.
There are several highly-portable telescopes available which have excellent optical performance and are well-worth considering. Some of them can be carried conveniently on holiday and are small enough to travel as cabin baggage.
If you live in an area with a lot of background light from street lights, or your view is severely restricted by trees or buildings then you may want to consider a telescope that will be easy to transport to a better site. Choose something that will travel comfortably in your car. If you have to travel by public transport then an ultra-portable may be more appropriate.
Computer-controlled mounts are becoming widely available, even on entry-level telescopes. They are proving very popular, particularly with beginners who value the help that computer control provides. It is like having a friendly expert alongside you to help find objects and show you where in the sky they are. Also, many of the computer controllers contain information about the objects which they will display for you while you are observing.
Computer control does not usually involve linking your telescope to a PC. Most computer control systems consist of a small handset linked to the telescope by a short cable. Motors and encoders are either built into the mount or are attached to it, making the telescope self-contained. Power is usually supplied by batteries (most commonly 12 volts) but cables to connect to car cigarette lighters and mains power supplies are also available. If you plan to use a mains power supply, remember that things get damp outdoors at night so make sure your supply is suitable for this. At the very least you must use it with an earth-leakage circuit breaker and protect it from the damp. A better alternative is to use a rechargeable battery pack. Neat units that will power your telescope for several nights are available with cigarette lighter sockets.
Most computer-controlled telescopes for beginners come with alt-azimuth mounts. These are lighter and easier to set up than equatorial mounts. In the section on mounts we said that equatorial mounts are easier to use, but with a computer to handle the tracking, the alt-az is easier.
Because it is light and compact, the alt-az mount is often coupled with a compact telescope tube. Good examples are the ETX range from Meade and the NexStar range from Celestron. Most of these are catadioptric telescopes but both manufacturers also offer short-tube refractors on computer-controlled mounts. These are particularly suitable for beginners and have many of the advantages of large binoculars without the disadvantages.
When you consider the quality of the optics in good astronomical telescopes and the amount of engineering going into them they represent very good value for money. With prices starting from less than £100 there is something to suit most pockets. But how much do you need to pay?
When I first wrote this web page I included some price ranges for guidance but telescope prices have fallen so rapidly it soon got out of date. For example, a four-inch refractor on a sturdy equatorial mount now costs less than £300 compared with over £500 just a few years ago.
Our on-line catalogue shows a wide range of telescopes and we recommend you browse through it to get an idea of what is available. Within the catalogue we have identified some of the more popular telescopes which you may find helpful in narrowing the range of choices.
In this brief introduction we have over-simplified the range of choices and there are many more combinations of price, type and quality than we have been able to include. However, our experience is that most people are able to decide for themselves which telescope is right for them with a little bit of help and guidance. The aim of this introduction has been to raise some of the issues you will need to consider and to help you frame the questions you will need to ask when talking to a retailer. For further information on some of the telescopes mentioned here please take a look at our on-line catalogue.
We also recommend looking at OUR RECOMMENDATION section in the online catalogue. It may help you narrow down the range of choices.
If you would like to discuss your own requirements we offer free, friendly advice and would be delighted to see you if you call in at Green Witch. Alternatively, give Lee a ring in Birstall on 01924 477719 or Neil in Gransden on 01767 677025, or send us an email. and we'll do our best to help.