How to Choose A Telescope for Astronomy

Telescopes are one of the most amazing technologies ever created by humans. First invented at the beginning of the 17th century, they have become affordable high-tech masterpieces that allow you to explore the wonders of the universe right from your backyard. Get ready to watch stars, planets, galaxies, nebulae and much more!

The Three Types of Telescopes

There are three basic types of telescopes: Refractor, reflector, and compound. All three types are designed to gather lots of starlight but go about that task in slightly different ways, giving each unique advantages and disadvantages.

Refractor Telescopes


refracting telescope

This is the telescope shape you’re
probably most familiar with. It has a big
lens at the front which passes light
directly into a mirror at the back
and into the eyepiece.


PROS:

+ Simple design, easy to use.

+ Works for objects on earth.

+ Sealed tube protects optics.

+ Sturdy and no maintenance.


CONS:

- Not ideal for faint objects.

- Can be heavy and bulky.

- Less value than reflector.

 

Reflector Telescopes


reflecting telescope

As the name suggests, this telescope
has a mirror at the end of its tube
which gathers light, before sending it
through another mirror
into the eyepiece.


PROS:

+ Great for viewing faint objects.

+ Very high image quality.

+ More value than refractors.

+ Compact and light weight.


CONS:

- Open tube can collect dust.

- Requires some maintenance.

- Doesn't work for earth objects

 

Compound Telescopes


sct telescope

This type of telescope is also called
catadioptric or
"Schmidt-Cassegrain" telescope.
It features two mirrors (one in the back and
one in the front) plus a lens.


PROS:

+ Great for viewing faint objects.

+ Works for objects on earth.

+ Sealed tube protects optics.

+ Great for astrophotography.


CONS:

- Usually more expensive.

- Bulky appearance.

- Second mirror reduces brightness.

 

✔ I want a beginner telescope: Refractor or reflector
✔ I want a rugged telescope that requires little or no maintenance: Refractor
✔ I want to also observe objects on earth (e.g. birds): Refractor or compound
✔ I want to view faint, deep sky objects: Reflector or compound
✔ I want the best image quality: Reflector or compound
✔ I want the biggest bang for my buck (value): Reflector
✔ I want to do astrophotography: Compound

 

Telescope Basics

There are four key things to look for when buying your telescope: Aperture, focal length, magnification, and computer control.

 

aperture   focallength

Aperture

Aperture is the diameter of the telescope’s mirror or lens. This is the single most important factor determining how much you can see with your telescope. In general, the bigger the telescope’s aperture the better! A bigger scope will let in more light allowing you to see fainter objects.

Takeaway: The bigger the aperture, the more light you can see. So get the biggest aperture within your budget.

 

Focal length

Focal length is the distance from the “focal point” of your telescope to the lens or mirror. It's not as important as aperture. But, the longer the focal length, the bigger objects will appear. So keep an eye on this. When in doubt, choose a telescope with both large aperture and focal length.

Takeaway: Focal length is less important than aperture, but it's still smart to chose a large focal length.

 
maginifcation   computercontrol

Magnification

Magnification is determined by your telescope’s focal length (see above) and your eyepiece. We have included the magnification you get with each reviewed telescope below. The bigger, the better. Tip: You can always upgrade to an eyepiece with more magnification later.

Takeaway: Magnification determines how big objects appear. Start with your telescope's included eyepiece. Later you can easily upgrade to a higher magnification eyepiece.

 

Computer Control

Lots of modern telescopes offer a built-in computer control which automatically points the telescope to interesting objects. It's a great feature which allows you to track down the celestial highlights you’re interested in quickly, track moving objects (i.e. for astrophotography), and more.

Takeaway: Computer control is the way to go. You can still manually find objects if you like, but computer tracking makes it easy to quickly find celestial highlights.

 

Telescope Mounts

The mount is almost as important as the optical tube itself. An unstable mount will hinder even the best telescope from delivering a quality image.
A mount that is too light will be jostled by the wind and cause your images to bounce.

Below is a quick overview of the four types of telescope mounts.
 
 
Alt-azimuth Mount
 
The simplest type of mount, it moves up, down, left, and right.
 
Dobsonian Mount
 
The least expensive type of mount, a Dobsonian mount is often combined as a set with reflector telescopes. The tube sits loosely in the mount, making it easy to carry the two parts. Amateur telescopes that are more than 16 inches across sit in a Dobsonian mount.
 
Equatorial Mount
 
This mount allows the telescope to follow the stars as they move across the sky. Originally, one of the mount's axes was aligned parallel to the Earth's axis and moved with a weight-driven clock drive. Today, many equatorial mounts use a motor to move them.
 
Go-to Mount
 
Using motors and an onboard computer, this type of mount will find and track a celestial target. These highly accurate, and expensive, systems often have large databases full of thousands of objects.