If you are in the market to buy a telescope, the chances are very high that you will stumble upon choosing between
- Refractor Telescope or
- Reflector Telescope
This article will walk you through the differences, pros, and cons of refractor and reflector telescopes for astrophotography.
Refractor telescopes rely on lenses and use the principle of refraction of light to enlarge an object and project the image on the eyepiece. The reflection law of glass is used in constructing the Reflector Telescope.
Refractor Telescope vs. Reflector Telescope and Their Differences
There are many substantial differences between Refractor and the Reflector telescope. The differences are given below:
|Refractor Telescope||Reflector Telescope|
|Refractor Telescope suffers from chromatic aberration.||No chromatic aberration is seen in the reflector telescope.|
|Lens sag is prominent in this type of telescope.||There is no lens sag in the Reflector telescope.|
|Image quality is relatively bad compared to reflector telescopes.||Very clear and sharp image quality.|
|Relatively harder to mount.||Relatively easier to mount.|
|Less chance of optical misalignment.||Optical misalignment happens frequently.|
|Relatively easy to use.||Relatively complex to use.|
|Very low maintenance is required.||Frequent maintenance is required.|
|The smaller size of the objective.||The larger size of the objective.|
|A bigger Refractor telescope is not feasible.||A bigger Reflector telescope is feasible.|
|A refractor telescope is lighter.||Reflector telescopes are a little bit heavier in weight.|
As the name suggests, refractor telescopes rely on lenses and use the principle of refraction of light to enlarge an object and project the image on the eyepiece. Refractor Telescopes first originated from Europe in the early 1600s.
The first refractor telescopes used the “Galilean Refractor” design. An objective made out of a bi-convex lens and an eyepiece made out of a bi-concave lens are used to form a magnified image. The main advantage of using the Galilean Refractor design is that we get an erect and true image in the left or right perception.
But if you pick up a relatively modern Refractor telescope, you will most possibly pick up a telescope constructed using the “Keplerian Refractor” design. Keplerian Refractor uses a convex lens in both objective and eyepiece.
Keplerian Refractor design produces an image using a bi-convex lens objective with an extended focal length and a bi-convex lens eyepiece placed behind the focal plane. As a result, a horizontally and vertically inverted image is produced.
Though the Keplerian Refractor produces an inverted image, it is still preferred over Galilean Refractor as a larger apparent field of view is provided by the Keplerian Refractor. Keplerian Refractors are also great for novice astronomers and are most commonly used.
Pros Of Using Refracting Telescopes:
- Refracting telescopes are very rugged. Therefore, after initial alignment, there are fewer chances of misalignment of their optical system.
- Refracting telescopes requires less maintenance.
- Easy to use.
- It can capture more detailed and stable images than reflecting telescopes of the same size.
Cons Of Using Refracting Telescopes:
There are some drawbacks of using refracting telescopes, which are stated below.
- Chromatic Aberration.
- Lens Sag.
- Spherical Aberration.
The reflector Telescope was mainly developed by Issac Newton in 1668. The reflection law of glass is used in constructing the Reflector Telescope. Newton’s design continues to be used widely in constructing modern reflector telescopes.
A concave mirror is positioned at the beginning of a large tube-shaped housing. The opposite end of the tube is left open to allow light to pass through the housing. A small mirror inclined at a 45-degree gradient is placed inside the tube. The light is then reflected by the mirror and projected towards the opening on the side of the telescope housing, which contains a convex lens eyepiece.
There is a limitation to this design. The small mirror upon which light is reflected the eyepiece tends to lessen the essential surface area of the objective slightly. But the reduction is very marginal.
Some people may find looking sideways at objects difficult. That is why a distinct method known as “Cassegrain Reflector” is used to project light in the direction of the eyepiece.
The Cassegrain Reflector method uses a small convex non-angled mirror. That small convex mirror reflects light towards the opening in the center of the objective mirror, which contains the convex lens eyepiece. As a result, we can observe objects looking at the back of the telescope.
Pros Of Reflector Telescope:
- Produced image is free from Chromatic Aberration
- Lens sag problem is non-existential in Reflector telescope
- Because of having a larger objective, more light can be captured by a reflector telescope. As a result, dimmer objects can be observed with more details and sharpness.
Cons Of Reflector Telescope:
Though reflector telescopes are good at what they do, there are a few cons.
- As reflector telescopes can easily be upscaled in size, the mirrors inside the telescope must be cleaned because of their open construction.
- Optics can get misaligned easily.
- Requires more maintenance
- Relatively hard to use as optics may require frequent alignment
Refractor Telescope Or Reflective Telescope Which One Is Better?
We learned that refractor telescopes suffer from chromatic aberration and lens sag problems. But Reflector telescopes do not suffer from any of these problems. And the picture quality is better on the reflector telescope thanks to its larger objective size.
Reflector telescopes dodge the chromatic aberration problem by using a convex mirror as the objective. And as mirrors can be supported from behind, they do not suffer from the sag problem as refractor telescopes. As a result, reflective telescopes can be much larger than refractor telescopes.
The production of a reflector telescope is much cheaper than a refractor telescope. Besides, reflector telescopes are also easier to mount because the back of the mirror can be used to attach to the mount.
So we can conclude that reflector telescopes have the upper hand over the refractive telescope mainly because most of the problems faced by the refractor telescope can be solved using the reflector telescope.
If you are looking for a telescope to use professionally, a reflector telescope is the one you should go with. They can capture more light and provide superior image quality over the refractor telescope.
And if you are a hobbyist, a refractor telescope is the perfect type of telescope for you because it can be compact and are much easier to maintain than reflector telescopes.