A telescope is an optical instrument which is used to magnify and enhance the view of distant objects. The objects could be either astronomical or terrestrial.
There are two types of telescopes: the reflecting and refracting telescopes. Both the reflecting and refracting telescopes differ from each other in their way of manipulating the incoming light rays so as to magnify the image.
Reflecting vs Refracting Telescopes
The main difference between Reflecting and Refracting Telescopes is that a reflecting telescope has a single or a combination of curved mirrors in order to reflect the light rays and form an image. On the other hand, an refracting telescope has a lens as its objective lens to form an image.
In a reflecting telescope, the main component is a mirror which bounces the light rays and then focuses it into a small area. On the other hand, a refracting telescope uses lenses to focus the light rays as it travels towards the other end of the telescope.
Comparison Table Between Reflecting and Refracting Telescopes
| Parameters of Comparison | Reflecting Telescopes | Refracting Telescopes |
| Definition | A telescope having either a single or a combination of curved mirrors that reflect the light rays and form an image. | An optical telescope having a lens as its objective lens in order to form an image. |
| Tube | It has an open tube which makes it vulnerable to dust, humidity, etc. | It has a closed tube that protects it against the effect of humidity and dust. |
| Light Gathering Power | It has a large mirror that has has more light collecting capacity. | It has a small diameter that has light collecting capacity. |
| Chromatic Aberrations | It suffers no chromatic aberrations (colored fringes around stars). | It suffers chromatic aberrations (colored fringes around stars). |
| Weight | It is heavy and bulky. | It is light and transportable. |
| Use | Have more use in the field of astronomy. | Have more use in the field of photography. |
What is Reflecting Telescopes
A reflecting telescope is an optical telescope that has either a single or a combination of curved mirrors used to reflect the light rays and form an image.
It consists of a primary mirror which is located at the lower end of the telescope tube and the front surface is coated with a very fine thin film of metal such as aluminum. The back side of the mirror is mostly made up of glass.
The primary mirror of a reflecting telescope reflects the light back to the focus. The primary mirror has either a concave spherical or a parabolic shape and when it reflects the light rays, the image gets inverted at the focal plane.
The reflecting telescope does not suffer chromatic aberrations as reflected light does not get dispersed according to its wavelength. The telescope tube is shorter in length hence reducing the cost of the tube.
The reflecting telescopes are heavy in weight, produce disappointing optical quality and it has an open tube which make it vulnerable to dust and humidity as compared to the refracting telescopes.
The Reflecting telescopes have their use in the field of astronomy research.
What is Refracting Telescopes
A refracting telescope is an optical telescope that uses a lens as its objective lens in order to form an image of a distant object.
The refracting telescope consists of two lenses, one is Objective and other is the eyepiece. The objective lens produces an image of a distant object at its focus point and the eyepiece lens magnifies the image formed.
A refracting telescope have good contrast and sharpness, are light and transportable and has a closed tube that protects it against the humidity and dust.
A refracting telescope suffers chromatic aberrations (colored fringes around stars), cannot be made of larger size and has a small diameter that has less light collecting capacity as compared to reflecting telescopes.
The Refracting telescopes have their use in the field of astronomy and photography and also in spy glasses. They are used in items like binoculars and camera lens systems because of their simple design and lower cost of construction.
Main Differences Between Reflecting and Refracting Telescopes
- A Reflecting telescope has either a single or a combination of curved mirrors that is used to reflect the light rays and form an image. On the other hand, a refracting telescope has a lens as its objective lens to form an image.
- Reflecting telescopes use mirrors whereas the refracting telescopes use lenses.
- Reflecting telescopes have less chromatic aberrations whereas the refracting telescopes have chromatic aberrations.
- Reflecting telescopes have disappointing optical quality whereas refracting telescopes have excellent contrast and sharpness.
- Reflecting telescopes have a large mirror that has more light collecting capacity whereas refracting telescopes have a small diameter that has less light collecting capacity.
- Reflecting telescopes are heavy and bulky whereas refracting telescopes are light and transportable.
- Reflecting telescopes can be made larger in size whereas this is not possible with the refracting telescopes.
- Reflecting telescopes have an open tube making it highly vulnerable to dust and humidity whereas refracting telescopes have a closed tube that protects it against humidity and dust.
- Reflecting telescopes have a lower cost of construction whereas the refracting telescopes have a higher cost of construction.
- Reflecting telescopes produce issues in their maintenance and cleaning whereas the refracting telescopes have nonexistent maintenance and cleaning issues.
- Reflecting telescopes are used in the field of astronomy whereas the refracting telescopes are used in the field of photography.
Conclusion
Both the reflecting and refracting telescopes differ from each other in terms of everything.
A reflecting telescope uses concave (bends inwards) mirrors. The light rays travel down the tube of the telescope where they get reflected up to the secondary mirror near the top of the telescope tube which hence, directs the light rays in the eyepiece.
A refracting telescope uses a convex (bends outwards) lens so as to collect, focus and magnify the light rays. The rays of light travel through the objective lens where they get focused at the focal length of the eyepiece lens.
References
- https://ieeexplore.ieee.org/abstract/document/8556766/