With Christmas getting close, I thought it would be a good time to do a short series on buying a telescope. This will be aimed at beginners and also someone who wants to buy a telescope for someone but may not be familiar with them. I am going to write this in 3 parts and in a way, I am going to work backwards. This article will explain telescopes, the choices you will have and how to pick the right one. In part 2, I will look at binoculars and why you might want to try a pair of binoculars first. Some people may not be ready to commit to a telescope or binoculars or they may have a child that is showing an interest in astronomy. In this case there are some other cheaper options which might be more suitable to get started. I’ll talk about this in the final part.
Buying a telescope can get very complicated very quickly, as there are a huge variety of choices out there. The first thing to know is that every telescope comes in 3 parts. The image bellow shows an example. At the bottom is the tripod. Most tripods are the same and you don’t need to worry too much about this bit. Once it’s steady it will be fine. Attached to the tripod is the mount. This is the part of the telescope that moves to point the telescope and there are a few types. Finally you have the optical tube of the telescope itself and there are also different options here. You can generally buy any type of tube with any type of mount, so I will cover each part separately.
Optical Tube
Optical tubes come in a many forms but for the beginner you really only need to know two. The reflector and the refractor. Some people think about a telescope as a device for magnifying the view of objects in the sky. To an extent that is true, but what one should really be concerned about is the light gathering power. You will often see 500X written on the box of a cheap telescope. I would avoid this. Really a telescope and the optical tube is designed to gather more light than your eye can and focus it into your eye. The better telescopes are the one with the wider lens or mirror. The picture above is a refractor. It has a lens at one end and an eyepiece at the other. The number you see associated with this is the size of the lens. For example the telescope above is 80mm or 3 inches. The larger the lens size fainter the objects you can see.
The next telescope tube which is pictured below is a reflector. There has an open end, with a large curved mirror at the bottom of the tube. This mirror focuses the light to a second mirror and into the eyepiece. The number associated with these telescopes is the size of the large mirror. The one bellow is 130 mm or 5 inches. In general these tubes are cheaper and similar to the refractor, the larger the mirror size the more light you gather and the fainter the objects you can see.
Refelector vs Refractor
The following table gives you a quick comparison of the different types of tube.
| Reflector (Mirror) | Refractor (Lens) |
| Larger mirror for the same price | Smaller lens for the same price |
| Better for deepsky objects | Better for planets and Moon |
| Better light gathering capacity | Less light gathering power |
| Open tube makes dust and moisture an issue | Closed tube means no dust or moisture |
| Mirrors can go out of alligment | No maintenance required |
| Heavy and bulky | Light and compact |
The Mount
The optical tube is the part you look through and gathers the light. This doesn’t mean we should forget about the mount that carries the telescope. There are two basic types. An alt – az mount and an equatorial mount.
Alt-Az Mount
The alt – az mount is the most simple mount. The mount moves up and down, left and right. An example of telescope on an alt-az mount is shown below. It is similar to a camera tripod.
Equatorial Mount
The other type of mount is called an equatorial mount. These mounts are more complicated. They are tilted at an angle. You set this angle so that the mount is lined up with the north celestial pole. This means that once you are pointing at a star you only need to move the mount in one direction to follow the star. Equatorial mounts are important for astrophotography but are probably over complicated for most beginners so a simple alt-az mount is probably the best choice.
Motorised (Go-To) Mounts
For both of the options above you will have the choice of buying a motorised, Go-To mount. These mounts will point the telescope to the object you want to see and will move the telescope to keep the object in the eyepiece. This can be really useful when trying to find dim objects or when doing astrophotography, when a tracking mount is essential. However, they also have downsides. They are more expensive and they can be very fiddly to set up and align. It will be another system you need to learn and they require power so you will need wither a power pack or extension lead. For beginners, using a manual mount also gives the opportunity to learn your way around the sky. If you know you will want to do astrophotography, and you have the budget then a go-to mount is the way to go. If you are a complete beginner and not sure about photography then I recommend a manual mount.
Dobsonian Telescope
Another type of telescope suitable for a beginner is a dobsonian telescope. This is a reflector type telescope on an a alt-az box style mount. They are very simple to use and are cheaper for the same size of telescope.
Some Things to Consider
There are a number of points to consider when buying a telescope. You should think about what you will use it for. In general the Moon and Planets are more suited to a refractor but deep sky objects are more suited to a reflector. You should also think about where you will use it and how you will get there. If you live in the country, you will likely have dark sky and can use it in your garden. However, if you live in a town you may need to travel some distance to use it. If this is case make sure your new telescope is light and easy enough to get in and out of your car.
Storage space can be an issue for some people. The last thing you want to do is to use it as a coat rack or trip over it and damage something. Resist the urge to buy something over complicated or too big until you get used to the hobby, otherwise you will likely get frustrated and give up. I’d also advise you to set your expectations early. I don’t want to be a downer, but you will never see images like you do in magazines or books with your eyes. No mater how big your telescope is, our eyes are not as sensitive as cameras are. Often the objects you will be looking at are nothing more than a smudge and you have to appreciate them for what they are while trying to tease out any details you can.
Budget can be a concern, particularly if you are only starting out in astronomy or if you have a child that is showing an interest in astronomy. You will need to spend around €200 to get a basic telescope that will give you some good views. It isn’t a good idea to try and buy a cheap telescope to get started. You or your child will get bad views, be disappointed by the view and you will be put off for life. In this case you are much better buying a pair of binoculars or even some books or apps to help you learn the sky first. I will cover both of these topics in part 2 and 3 of this series.
I strongly recommend you don’t purchase a telescope from anywhere other than an astronomy shop. The reasons are, in general the telescopes in toy shops and other high street stores are not good quality. They will likely be handled incorrectly and could be damaged when you get them. Probably the most important reason is that you will get much better advice and aftersales service from an astronomy shop. Best of luck with buying your first telescope!
Paul Smith 