To me, a telescope is the single most important purchase you can make (that’s right, even more than a house, car or a TV) and I want to make sure you get the right one. The biggest mistake people make when buying a telescope is buying one that doesn’t fit them. They end up spending WAY too much money on something they end up never using.
A telescope is a tool, just like a computer or a hand saw. When using any tool, you need to have some idea of what you want to do with it. The astronomical telescope’s core job is to do one thing: gather photons from faint sources and focus them into an image bright enough for your eye to see or a camera to record.
Since there is a vast array of objects that can be focused on in the universe, there is no ideal type of telescope that does a good job of imaging all celestial objects available.
For example, planets are best viewed through refracting telescopes where the focal lengths are longer, magnifications are higher and the optics provide generally sharper views. Galaxies and nebulae, on the other hand, are very spread out and dim compared to planets; they are best viewed through larger aperture telescopes where more photons are collected in order to make these very dim objects as bright as possible. Because large aperature lenses are expensive, the larger diameter telescopes tend to have mirrors in them (which cost much less to manufacture).
Planets are much brighter than nebulae so you don’t need a large diameter lens to collect more photons. Here you’re more interested in detail so you can see things like the bands of Jupiter or the polar caps on Mars. For this, optical quality and good, solid mounts are more important. Refractors are generally used in planetary observing although there are many that are well suited for deep sky objects.
On the other hand, galaxies, star clusters and nebulae are spread out across the sky; in some cases they are larger than your thumb held out at arms length. They are also very, very dim. To observe these objects, you need to collect as many photons of light that come from these things as you can and to do that, you need a light bucket – as big as you can afford (light bucket is just a term for large diameter). Large reflectors are best for these objects and magnifications are usually much lower because you’re more interested in covering as much sky as you can to see the whole galaxy or nebula. These telescopes are also shorter than refractors because they focus the light into an image in a much shorter distance.
Because of the variety of celestial objects that can be seen, most sky-nerds (like myself) have many telescopes, each one better suited to all the different things you can see and each with their own strengths and weaknesses.
If I want to observe the planets, I use my refractor because I want crisp, sharp images for detail. If I’m trying to see the Orion nebula, I want a reflector that shows as much of the sky as possible and collects lots of light so I see a bright image.
If you are considering your first telescope purchase I urge you to think about what exactly you want to see through one. Also put this purchase in the context of the kind of person you are.
- Do you have a casual interest in the sky or has the astronomy bug bitten you hard?
- How familiar are you with the night sky? Do you know much about where these objects are or do you need help? Do you need a telescope to find planets, galaxies, etc. for you?
- Are you lazy? This is a big one for me. I’ll sometimes feel like going out and observing but if it’s a big hassle to set up my scope, I just forget it. If it weren’t for my easy-to-use scopes, I wouldn’t go out anywhere near as much.
Most people reading this are probably waiting for me to tell them what telescope to buy.
My first piece of advice is to take your time. Don’t be in a hurry to buy the wrong telescope. If you’re all that anxious, go outside and try to find some naked-eye objects like a planet or the Orion nebula.
The universe isn’t going anywhere (if it is, then you have bigger problems to think about that what telescope to buy) and a little time taken to think about these issues will pay off, I promise. I’ve seen way too many people spend thousands of dollars on a great telescope that just sits in the garage.
I’m not going to give specific recommendations until I’ve had you think about these questions:
- Are you more interested in planets or deep-sky objects like galaxies?
- Are you good with computers and technical stuff? If yes, then you can consider a computer controlled telescope. If no, get something simple, like a Dobsonian (I’ll go over the different telescope types in another article, for now, just think about these questions).
- Are you impatient? Observing through a telescope is a peaceful, serene activity. While many, many amateur astronomers try to whip through as many objects as they can on a given night, beginners should always strive to take their time. Beginners are on a learning curve – they are learning the night sky, its rhythms and cycles, the celestial objects it contains and their positions as well as how to handle the telescope and find things through it. There’s a lot going on and to learn it all, you must be patient.
- What are your goals? Do you just want to see cool stuff or are you genuinely interested in learning about the night sky and how to use a telescope? If you just want to see cool stuff, go to NASA’s web site, the Astronomy Picture of the Day site, or buy a planetarium program for your PC. Nothing you see through a telescope in your backyard will ever compete with that. You should buy a telescope because you want to personally connect with the universe.
You're on a wonderful journey, one that ends with you owning a telescope, a tool that will put the farthest reaches of the universe right on your retina. I want to make sure tool does its job and makes you happy, because there's no greater activity to pursue on a Sunday night than exploring the universe we live in. Even if Game of Thrones is on.