Are Telescopes Concave Or Convex?

A telescope is a device that magnifies distant objects. The image produced by a telescope is called a telescopic image.

Telescopes come in two types: refractors and reflectors. Refractors focus light using lenses, whereas reflectors use mirrors.

Are Telescopes Concave Or Convex

The first known telescope was built in the 15th century by Chinese astronomers.

It consisted of an objective lens and a tube with a mirror at one end to direct the image onto a screen.

This type of telescope is still used today for observing planets and stars.

A modern telescope consists of several parts: (1) a primary mirror; (2) a secondary mirror; (3) a focusing mechanism; (4) eyepieces; and (5) a computerized mount.

The optics of a telescope can be made from glass or plastic.

Glass telescopes are more expensive than plastic ones because they must be ground into shape and polished.

Plastic telescopes have no moving parts, so they are less expensive to make. They also tend to be lighter and easier to carry around.

The focal length of a telescope refers to the distance the light travels through the scope from one end to the other, and it has a drastic effect on the nature of the image before you.

A longer focal length will give you a smaller field of view, but greater magnification, while a shorter focal length offers up a wide FoV (awesome for stargazing) but a limited magnification.

The most important parts of a telescope are the primary mirror and the secondary mirror as they are what allow you to see into the stars, magnifying everything. 

Whether these mirrors are concave or convex is the question…

Concave Vs. Convex


In astronomy, a concave mirror is a curved surface that reflects incoming light rays back towards the source.

In contrast, a convex mirror is a curved surface that bends incoming light rays outwards.

Both types of mirrors are commonly found in optical instruments such as telescopes.

A concave mirror has its center of curvature located closer to the observer than does a convex mirror.

When light enters a concave mirror, it is reflected off the innermost portion of the mirror’s surface.

On the other hand, a convex mirror has its center of curve located farther from the observer than does a concave mirror.

Light entering a convex mirror is reflected off the outermost portion of the mirror.

As a result, a concave mirror produces sharper images than a convex mirror.

Refractor Vs. Reflector

A refractor is a telescope that uses lenses instead of mirrors to form an enlarged image of the sky.

Refracting telescopes produce much clearer images than reflecting telescopes do.

However, refractors require more skill to operate than do reflecting telescopes.

A reflector, on the other hand, is capable of gathering a lot more light than a refractor, which makes them the ideal choice for observing deep space objects!

Refractors use lenses to focus light on a small spot called the “image” where the light then travels to your eye.

Refractors usually cost less than reflectors, but they’re not as easy to use.

Reflectors use mirrors to create an enlarged image.

These telescopes are the more user friendly of the two, but if you want pristine precision, a refractor’s the one for you.

These lenses can also be either concave or convex

Are Telescopes Concave Or Convex?

Are Telescopes Concave Or Convex?

Within a telescope, there are two mirrors. Typically the mirrors in a telescope are convex.

That means that they bend the path of light outward. This makes objects appear larger. 

However, there are some exceptions. Some telescopes have a concave mirror as well as a convex one.

The reason for this is that the light coming from the star goes straight through the lens, then turns 90 degrees before hitting the mirror.

This allows the light to go straight through the lens without being bent by the mirror.

This type of telescope is known as a catadioptric. Catadioptric telescopes are used primarily for observing planets.

Telescopes must have at least one mirror that is convex. This is because when light hits a convex mirror, it is reflected in all directions.

If the mirror were flat, only half of the light would hit the next mirror.

Catadioptric Telescopes

The first catadioptric telescope was invented by Galileo Galilei in 1610. It consisted of a convex and a concave mirror inside a tube.

In 18th century Europe, astronomers began using a new kind of telescope. They built them with a concave mirror and a convex mirror.

This allowed them to see double stars (stars that are close together).

Later, engineers started building telescopes with three mirrors: a concave primary mirror, a convex secondary mirror, and a third mirror that was convex.

This design made it possible to observe very faint objects.

Modern telescopes often include many different kinds of lenses. For example, you might find a telescope with a convex lens, a concave lens, and a spherical lens.

Each of these lenses focuses light onto a point. In addition, each lens bends the light in a certain way.

By combining several lenses, you can make a telescope that will magnify distant objects.

Types Of Lenses

Lenses come in many shapes and sizes. There are four main types of lenses: spherical, cylindrical, plano-concave, and plano-convex.

Spherical lenses are round. Spherical lenses are best for making large telescopes.

Cylindrical lenses are shaped like cylinders. Cylindrical lenses are best for making microscopes.

Plano-concave lenses are shaped like a plane with a curved edge. Plano-concave lenses are best for making binoculars.

Plano-convex lenses are shaped like a flat plane with a curved edge on both sides. Plano-convexes are best for making eyeglasses. 

Telescope Types

As well as the catadioptric telescope, there are many different types of telescopes. Here we’ll take a brief look at three of them:


Refractors use lenses to gather light and focus it onto a small spot called the image. Refractors are very popular among beginners.

They are usually quite expensive and quite tricky to get to grips with.

They produce a sharp image, that perhaps isn’t as bright as the image seen through a good reflector.


Reflectors use mirrors to gather light and focus onto a small spot called an image.

Reflectors are normally more affordable than refractors, and they’re easier to use too.

Though they may provide a bright image, it won’t be as crisp as the image provided by a refractor.

Cassegrains – Cassegrain telescopes are similar to reflectors.

They both use mirrors to gather light. But Cassegrains differ from reflectors in that they use a secondary mirror to collect the light.

This reduces glare and creates a brighter image.

The most common type of telescope is a Newtonian reflector.

It’s the cheapest way to get started with astronomy. It’s also the easiest to use.

You just need to know how to hold the telescope properly.

The second most common type of telescope, the refractor, is slightly more complicated to use. But once you’ve mastered it, you will see amazing things.

Final Thoughts

So now you know that telescopes must always have at least one convex lens/mirror.

The convex lens/mirror is the most important base for reflecting back on the stars.

However, the second lens/mirror can be concave. If you want to make your telescope even more powerful, add a third lens/mirror.

Finally, if you want to make your scope even more powerful, add another lens/mirror.

Gordon Watts