Reflecting Telescope Explained

Reflecting Telescope Explained

Astronomy is a fascinating hobby to get into. However, you can only go so far with an app on your phone.

To become a true astronomy hobbyist, you will eventually need to get your own telescope. 

However, there are hundreds of telescopes out there. How do you choose one?

If you are a bit overwhelmed by your choices, you have come to the right place.

This guide will cover everything you need to know about reflector telescopes. 

A reflecting telescope is an optical instrument that produces magnified images of distant objects.

More specifically, it is a type of telescope that uses mirrors to collect and reflect light to form an image. 

In this guide, you will learn what a reflecting telescope is and how it works.

We will cover all the different parts of the telescope and compare it to different models you will find on the market. 

Lastly, learn how to use a reflecting telescope in a few easy steps. If you are ready to learn more, keep on reading. 

What Is a Reflecting Telescope

What Is a Reflecting Telescope

A reflecting telescope is a type of optical instrument that uses a mirror or a series of mirrors to collect and reflect light to form an image.

Reflecting telescopes allow you to see faraway objects in the night sky up close. 

In the 17th century, Isaac Newton invented the reflecting telescope, which is why many people also call this instrument the Newtonian telescope. 

This instrument has adopted the name of a reflecting telescope because the mirrors reflect the light back towards the focal point instead of refracting it.

People also call this model an open telescope since the mirrors are exposed to the outside air, dust and humidity. 

Due to this feature, users will need to clean the telescope more frequently than other models.

However, reflecting telescopes are popular since they are easy to build and are very affordable.

When it comes to the optical quality of the instrument, reflecting telescopes have a bit more power.

Unlike other telescopes, you can explore short and long wavelength regions as well as the electromagnetic spectrum’s visible region.

In other words, you can see a lot more with a reflecting telescope. 

Due to this reason, most professional astronomers use reflecting telescopes. As a hobbyist, you can pick up a reflecting telescope for around $300 to $500.  

How Does It Work

How Does It Work

Now that we know what a reflecting telescope is let’s see how it works.

While it may seem a bit daunting to use one as a beginner, this section will help break down the technology behind the instrument.

Light reflection works in a very predictable way. When light hits an object that it can’t pass through, it reflects and bounces back.

When that object or surface is smooth and flat, the light reflects almost in the exact same way at the same angle every time.

Reflector telescopes take advantage of this phenomenon.

Inside the body of a reflector telescope, you will find a series of curved mirrors (or simply a single mirror). These mirrors bend the incoming light and create parallel light rays.

The instrument then converges these light rays into a single focus beam. 

With these light rays, the telescope can produce an image. There are a few different kinds of reflectors that you will find in different models. 

While most reflector telescopes have the same basic components, there are many different kinds of mirrors that are different shapes.

It all depends on the model. Let’s take a look at some of the most common types of reflectors. 

Types of Reflectors 

  • Newtonian reflector: Newtonian reflectors use a flat mirror to reflect the light rays back and out towards the telescope’s eyepiece. 
  • Cassegrain reflector: Cassegrain reflector telescopes use two mirrors. The primary mirror has a hole in the middle, while the secondary mirror is convex. 
  • Coude reflector: Similar to Cassegrain reflector telescopes, Coude reflectors have two mirrors. The primary mirror is angled, while the secondary mirror is convex. The telescope uses these mirrors to reflect the light away and towards a focal point. 

Parts of the Reflecting Telescope 

In this section, we will review all of the parts of a reflecting telescope.

Seven essential parts play major roles: the tube, mount/tripod, eyepiece, primary mirror, secondary mirror, counterweight, and motor. Let’s take a look. 

The Tube

The telescope tube is the main body of the telescope. Some of the most important components are inside the tube, such as the primary and secondary mirrors.

Telescope tubes are typically different sizes from one model to another, but many tubes will have a diameter of around 8 inches. 

A telescope tube also plays an important role in the focal length. Users can use the knob on the body of the tube to improve the focal length. 

The Mount and Tripod

The telescope mount and tripod arguably have the most important job; to support the instrument. These components are what allow you to move the telescope up and down and left to right.

Furthermore, the tripod stabilizes the telescope, which allows you to use it hands-free.

The Eyepiece

Another important component of the reflecting telescope is the eyepiece. The eyepiece is where you look to see the magnified image of the object you are viewing. 

Not only do you look through the eyepiece to see the telescopic image, but the eyepiece also determines the magnification power of the telescope. 

Furthermore, you can also switch out the eyepieces for different pieces. There are many different kinds of eyepieces that you can use that will give you different magnification powers.

Lastly, on most eyepieces, you can also adjust the piece to focus the image. 

The Primary Mirror

The primary mirror, located inside the telescope tube, reflects light back towards the eyepiece. These mirrors typically have a parabolic shape or are concave.

When this mirror reflects the light that enters the telescope, it produces and inverts the image. 

You can usually find the primary mirror near the back end of the telescope. The front of the mirror is coated with a thin layer of metal while the back is glass. 

The Secondary Mirror

Not all reflecting telescopes have secondary mirrors. Many of them will only have a single mirror. However, for the ones that do, the main job of a secondary mirror is to re-direct light. 

The secondary mirror is located in the pathway that the primary mirror sends the light down.

When the light is re-directed, the light ends up being extended, and the secondary mirror modifies the final magnified image. 

The Counterweight 

Many telescopes will also have counterweights. The main job of the counterweight is to prevent the instrument from leaning downwards due to gravity.

To use the counterweight, you attach it to the extension bar on the telescope. To perfectly balance the weight, the counterweight needs to weigh the same as the telescope tube. 


Not all telescopes will have motors, but some will. A motor is a powered component that allows you to track a star or other terrestrial objects with your telescope.

The motor will account for the earth’s rotation and automatically follow whatever object you are aiming at. 

How To Use a Reflecting Telescope 

How To Use a Reflecting Telescope 

Now that you are familiar with all of the parts of a reflecting telescope, it is time to learn how to use one.

You will need a few things, including your telescope, eyepieces, tripod, star charts, and a light source.

Something to keep in mind is that you will need a solar filter if you want to use your telescope during the day.

It can be dangerous to look through one without a filter. 

  • Review the owner’s manual of your telescope. The first thing you should do is review the owner’s manual of the telescope. Each telescope is different and has a lot of parts. Reviewing the manual will help you become familiar with the main components of the machine. 
  • Practice using the mount, tripod, and knobs. Before heading out to your location, make sure to practice using the different parts of your telescope, including the mount, tripod, and focus knobs. Practice setting up the tripod and moving the telescope on the mount. Furthermore, try to play with the focus knobs and practice attaching different eyepieces and locking them. 
  • Become familiar with the finderscope. The next thing you need to do is to get familiar with the finderscope. Ensure you know where all the screws are since you might be adjusting it out on the field. 
  • Study star charts. When you are out on location, you won’t want to do anything that will re-adjust your eyes. To see the stars clearly at night, you shouldn’t use a bright light source to look at start charts either on your phone or with a flashlight. For this reason, it will be a good idea to study star charts ahead of time, so you won’t have to refer to them a lot. 
  • Find the perfect location. Now that you have everything you need, you need to find the perfect location. Try to find a remote area away from city lights. Make sure no tall trees or buildings are blocking your view. However, try to find a spot where you can see the moon. The moonlight will help you set up your telescope in the dark.
  • Set your telescope up. Set up your tripod, mount your telescope, and remove the lens cap. Then, point it towards the sky.
  • Attach the lowest powered eyepiece to your telescope. If you have multiple eyepieces, attach the lowest powered eyepiece. If you only have one eyepiece, don’t worry about this step. 
  • Choose an object to study. Now you can look at the sky and choose the object you want to observe. Once you find one, point your telescope towards it. 
  • Use the finderscope to focus on the object. Now you can use your finderscope and adjust it so that the object is in the center of the lens. 
  • Look through the eyepiece and observe. Everything is set up now. Look through your telescope and enjoy the view. If you find that the object is out of focus, simply adjust the focus knob until it is clear. 
  • Replace the eyepiece. If you have multiple eyepieces, attach the high-powered piece if you want to look at something more closely. 

How Does It Compare to Other Telescopes? 

How Does It Compare to Other Telescopes? 

Many astronomers use reflecting telescopes to study the night sky. However, there are a few different kinds of telescopes out there.

So how do reflecting telescopes compare to other models on the market? 

Let’s look at a few factors such as price, technology, image quality, and how they compare to others. 


Compared to other telescopes, reflecting telescopes are some of the most affordable optical instruments available.

You can buy a good-quality one for around $300 to $500 and a high-quality one for above $500. 

The other main kind of telescope is called a refractor telescope. These telescopes cost anywhere from $500 to $1500. 

Comparatively speaking, if budget is an important factor for you, a reflector telescope will be a good choice.

You will be able to invest in a good-quality instrument for an affordable price. 

One of the main reasons why reflective telescopes are so affordable is that the mirrors are cheap to make compared to the lenses you find in other telescopes.


As we mentioned above, reflecting telescopes work with mirrors. Mostly all types of telescopes either use mirrors, lenses, or a combination of both. 

Refractive telescopes, the other main type of telescope, generally have two lenses; an objective lens and an eyepiece lens. Instead of reflecting light, these lenses refract and magnify light.

The objective lens collects the light and converges it to a main focal point. The eyepiece lens is responsible for determining the magnification power of the telescope. 

Something similar between the two kinds of telescopes is that you can replace the eyepieces. This feature is helpful when you want to change the magnification power and look at objects more close-up. 

Optical Quality 

While reflecting telescopes do not experience chromatic aberration, a type of coloured image distortion, you may see some fuzzy images while using a reflective telescope.

Since the mirrors are open to the elements, some air currents could travel through the tube and cause some image blur. 

However, these models let in a lot more light than other types, producing images with more detail. 

When it comes to the optical quality of refractor telescopes, you will notice that the image has very high contrast and sharpness.

However, you may notice some image distortion due to chromatic aberration. 

Ease of Use 

For a beginner, reflector telescopes may be difficult to maintain. Since the mirrors are open to the air, dust and humidity, the mirrors may become less reflective as the years go by.

Telescopes that use lenses instead of mirrors will be easier to maintain. 


A reflecting telescope uses a mirror or a series of mirrors to collect and reflect light back to the eyepiece.

It then uses this light to form a magnified image of a terrestrial object. 

Isaac Newton invented the reflective telescope in the 17th century, and it is now one of the most widely used models for studying the night sky.

These telescopes use a concept called light reflection. When light hits an object that it can’t pass through, it simply bounces back in a predictable direction.

The mirrors inside reflective telescopes bend the incoming light rays and converge them into a single focus beam to form an image. 

Compared to other telescopes, reflecting telescopes are more affordable. Instead of lenses, they use mirrors, and they can collect a lot more light than other models.