All you need to know to buy your first telescope
There are plenty of excellent reasons to own a telescope, and even an inexpensive one will provide great views of the moon and planets from the most light polluted skies (trust me, I live in Los Angeles!). Shopping for telescopes presents a myriad of options and features for a newcommer, but fortunately by following a few simple suggestions your first telescope will be one that you enjoy using over and over again to view the night sky.
TL;DR: Get a reflector style telescope that is 4"-6" in diameter with a manual azimuth-elevation mount. A telescope of that size will only run you couple hundred dollars and is plenty big enough to see craters and mountains on the moon, details on Jupiter and Saturn, and some star clusters and galaxies even from a light-polluted city.
The most important thing to know when buying a beginner telescope is that a bigger diameter will get you better performance. Think of a telescope as a bucket that fills up with light. The bigger the diameter of the bucket, the more light it can collect. And the more light it collects, the better you can see far away objects in the sky. Because diameter is so important, telescopes are typically marketed by their diamter (i.e. a 6" telescope is 6" in diameter).
Although the big diameter telescopes are impressive, you don’t need one of those to get started. Plan to buy something in the 4"–6" range. That will allow you to see craters on the moon, rings around Saturn, the moons of Jupiter, and even some of the brighter star clusters and nebulas in the sky. A 6" telescope will cost a bit more, but you’ll be able to see dim objects like nebula and galaxies better. I don’t think there’s any reason to go bigger than that for a first telescope, I’ve been rockin’ a 6" telescope for years and it does everything I need it to.
There are two main styles of telescopes available: refractors and reflectors.
The difference is how they collect light. A refractor telescope uses a large glass lens to collect and focus the light. This is the same kind of telescope Galileo used 500 years ago and is probably the image you see in your head when you think of a telescope. Refractors have their place but I don’t recommend one for a beginner. It’s challenging to make large precision lenses so refractors are much more expensive for a given diameter.
Reflector telescopes are, by far, the more common variety. Invented by none other than Isaac Newton, reflectors use a curved mirror placed in the back of the telescope to focus light. The light is then redirected out the side of the telescope by a second flat mirror. Large mirrors are easier to make than lenses and don’t suffer from a condition called chromatic aberration which is a problem with refractors.
There are a couple of different flavors of reflectors. The most common type, described above, is a Newtonian reflector. There are more complex configurations called Cassegrain telescopes (of which there are even more subcategories) that redirect light back out the rear of the telescope with a second curved mirror. The added complexity costs money so expect to spend at least a few hundred dollars more for a Cassegrain style. The benefit of Cassegrains is that they can be made shorter than their Newtonian cousins so you might consider a Cassegrain if the storage size is important to you. But I still recommend Newtonians for their relative simplicity and cost efficiency.
There are also two main types of mounting configurations for telescopes: azimuth-elevation (az-el for short) and equatorial.
Az-el mounts are the simpler of the two. They basically have one axis that rotates left-right (the azimuth direction) and another that rotates up and down (the elevation direction). Doesn’t get much simpler than that! I sometimes refer to az-els as point-and-shoot mounts because that’s about all the skill it takes to set one up.
You’ll notice that ‘Dobsonian’ style mounts are popular for larger reflectors. They are simple to use and don’t require a tripod to mount the telescope on top of so I’m a fan. Just note that they function the same way as any other az-el mounts.
The big disadvantage of an az-el is that the rotation axes are not aligned with how the sky moves at night. If you watch the sky long enough you’ll notice that all the stars appear to rotate around a point marked by Polaris, a.k.a the North Star. By pure coincidence, the rotation axis of Earth happens to point at Polaris. In an equatorial mount, one axis of rotation is aligned with the rotation axis of the earth (i.e. the axis points at the North Star), and the other rotates perpendicularly. By doing this, it becomes very easy to follow objects in the sky over time. This is really important if you’re doing astrophotography, but much less so if you’re just looking with your own eyes.
For a beginner, just get an az-el, it’ll be simpler to set up and you’ll probably enjoy using the telescope more because of that.
You might also see mounts with go-to functionality. This means the mount has a computer and some motors so it can point itself anywhere in the sky. That might sound alluring, but they are generally more expensive, more complex, less transportable, take more time to set up, and require a power source. And most importantly, they rob you of one of my favorite parts of amateur astronomy: actually learning where things are in the sky and how they move.
A couple more things to consider: the telescope you use the most is the best one for you. Even if you can afford a big state of the art instrument, if it's hard to assemble and setup you may never end up using it. A smaller telescope that has most of the capability of a larger one, but is easier to use, is often the better choice in the long run.
Lastly, there are a number of well-known amateur astronomy brands including Orion, Celestron, and Meade. For an entry level telescope don’t get too worked up in the quality of one brand versus another. For a given size of telescope they will likely have similar performance at the lower price ranges.
In summary, a simple 4"-6" diameter reflecting telescope will cover about all the bases for a beginner amateur astronomer and won’t break the bank.
I admit I might be a little biased in my conclusion. I’ve owned a 6" diameter Dobsonian telescope for most of my adult life. I’ve looked through plenty of bigger and more capable instruments over the years, but that “little” telescope has been my gateway to the universe. I’ve gone on adventures to the moon, rediscovered the secrets of the outer planets, and flown through immense starfield with that telescope. And frankly, what more could you ask for?
Here are a few places to get started with beginner telescopes that fit my recommendations. These links are only intended to provide some context around what I discussed above. They are not affiliate links, nor do I intend to endorse a particular brand over another.
Here’s a nice little 4.5" Dobsonian style telescope from Orion that checks all the boxes I talked about above. Its small, compact, and easy to use. If you want to scale up there’s a 6" version too. Meade has a similar product line too.
There are some other tripod mounted options that are the same size. I realized while looking for suitable telescopes that most tripod mounted beginner telescopes are either equatorial mounted or have computerized go-to functionality. Like I said above, I’d avoid those features even if you can afford them. Its added complexity you don’t need in a beginner scope.
If you have the money but not a lot of space you might try a 6" Schmidt-Cassegrain style telescope like this one from Celestron. Keep in mind this one doesn’t come with a tripod so that’ll be extra
Evan Hilgemann is a mechanical engineer at NASA’s Jet Propulsion Laboratory and a telescope operator at Griffith Observatory. You might also enjoy Explore & Observe, his email newsletter on modern day exploration of earth and space.
This work was done as a private venture and not in the author’s capacity as an employee of the Jet Propulsion Laboratory, California Institute of Technology. Any views and opinions expressed herein do not necessarily state or reflect those of NASA, JPL, or the California Institute of Technology
