What are the 3 Main Types of Optical Telescopes 2021?

types of optical telescopes

There are many different types of telescopes, classified according to their design, features, and location of placement. For example; 

  • Optical telescopes, 
  • Radio telescopes, 
  • Infrared telescopes,
  • X-ray telescopes, 
  • Gamma-ray telescopes. 

Above mentioned telescopes use their different wavelength/frequency of the electromagnetic spectrum. Such as Radio telescopes use radio frequency and Optical telescopes use visible lights in the band of the electromagnetic spectrum. 

Some of these telescopes are also classified into sub-categories; such as there are 3 main types of optical telescopes:

  • Refractor type telescope – it uses lenses.
  • Reflector type telescope – it uses mirrors.
  • Compound or Catadioptric type telescope – it uses lenses and mirrors.

Some telescopes are categorized according to the task they perform; such as ‘solar telescopes’ are mainly used to observe the sun. But here in this article, we have explained about “types of optical telescopes” that are commonly used by people. 

Simple Meaning of Telescope

A telescope is a device that makes distant-objects appear bigger and nearer so that we can explore farther objects clearly. Basically, telescopes observe objects by emission, absorption, or reflection of different radiations present on the electromagnetic spectrum. 

The telescopes detect and collect electromagnetic lights. But their types depend on what type of frequency/wavelengths astronomers are collecting in the band of the electromagnetic spectrum. And according to this, there may be different types of telescopes; such as X-ray telescopes, Ultraviolet telescopes, Optical telescopes, Radio telescopes, etc. 

Types of Optical Telescopes

There are 3 main different types of optical telescopes:

  1. Refracting telescope
  2. Reflecting telescope
  3. Catadioptric or compound telescopes 

These three main types of telescopes also have been divided into their sub-types according to the area of performance. They have their own separate benefits and can be used by professionals as well as amateurs (beginners). 

Refracting Telescope

A refracting telescope is also known as a refractor or a dioptric telescope. It uses lenses to refract light and form an image. 

The first invented telescope was a refracting type telescope. Its patent was submitted to Netherland Government by a spectacle maker ‘Hans Lippershey’ in 1608. Though the actual inventor is unknown. 

Galileo Galilei heard about this telescope and he created his own refracting telescope.

refracting telescopes

Advantageous of Refractor

  1. For the same quality of images, the refractor would be smaller in size. It forms a steady and sharp image when compared to the same size of a reflector telescope. 
  2. It needs less or almost no cleaning. 
  3. The set up of a refractor type telescope is very easy. 

Disadvantageous of Refractor

  1. One of the main disadvantages of a refractor telescope is that it creates ‘chromatic aberration’. It happens because the lens refracts or bends the lights. Chromatic aberration or chromatic distortion is a phenomenon of a lens, not able to focus all colors at a single point. This effect produces deviation in colors or a rainbow of colors around the image. 

Reflecting telescope

A reflecting telescope is also known as a reflector or a catoptric telescope. It uses mirrors that reflect light and form an image. 

Soon after the discovery of a refracting telescope, the scientists thought to use a mirror instead of a lens for the Objective (light-gathering element). Isaac Newton built the first reflecting type telescope in 1668 and thus it is known as a Newtonian Reflector.

reflecting type telescopes

Advantageous of Reflector

  1. A reflector type telescope does not have the effect of ‘chromatic aberration’ because it uses mirrors. The used mirror reflects the light in the same direction. 
  2. The objective mirror is on the backside so it can use a larger mirror easily. 
  3. This type of telescope is cheaper compare to a refractor type of the same size. 

Disadvantageous of Reflector

  1. As its tube is open, so a reflector needs frequent cleaning.

Catadioptric telescope

Catadioptric telescope is also known as a compound telescope. It uses a combination of mirrors and lenses to form an image. It gets used because it removes errors caused by lenses and mirrors. 

Which types of telescopes beginners should use?

If you are a beginner and looking for a telescope for astrophotography or viewing planets then you should consider the following points according to your need. 

Must check it:- 5 Best Celestron Telescopes for Beginners 2021

Reason to select a Reflector:-

You can go for a reflector telescope because it is cheaper (cost-effective). But it needs more maintenance and cleaning. 

Reason to select a Refractor:-

It is compact in size and does not need adjustment of the lens. But it is costlier.  


So these were the 3 main types of optical telescopes. If you are willing to purchase for celestial photography, then must check above mentioned reasons before buying a telescope.