When you start researching the telescopes, many telescopes mention in their description that the telescope has spherical mirrors or a parabolic mirror. What exactly are Spherical vs Parabolic Mirror differences? We will see the details in this article.
So, usually, the specifications of mirror types are mentioned in reflecting & Cata-dioptric type telescopes. If you don’t know the different types of telescopes then read this article.
What is a Spherical mirror?
Spherical mirrors have a spherical shape. They are easy to manufacture & are cheaper. The two types of spherical mirrors are the concave mirror and the convex mirror. The concave mirrors are used inside a telescope.
When parallel light rays fall on the concave mirror. The reflected light will not focus on a single point. Instead, it will focus on multiple points. Because of this, you will notice the spherical aberrations in the images. When the size of the mirror increases focusing on a single point by these mirrors gets much more difficult. So, you will see more spherical aberrations with a bigger spherical mirror.
Usually, the longer focal length of a telescope minimizes the effect of spherical aberrations. So, most telescopes that use spherical mirrors will have a longer focal length of 8 to 10. Mostly, spherical mirrors will be used in the small aperture telescopes below 150mm.
What is a Parabolic mirror?
Parabolic mirrors are not perfectly round mirrors but they are in the shape of a parabola. When a parallel light falls on these mirrors and is reflected, the light passes through a single focal point ultimately producing a sharper image of an object.
Parabolic mirrors are difficult to manufacture & have a higher manufacturing cost. That’s why telescopes with parabolic mirrors are expensive compared to the spherical mirror telescope.
The images you will see with the parabolic mirrors will be 60 to 70% brighter and sharper than a telescope with a spherical mirror. Just because parabolic mirrors give sharp images that don’t mean they are perfect. Parabolic mirrors also suffer from aberration but not as much as spherical mirrors.
Just because the spherical mirrors have aberrations that don’t mean they are not effective. Many Cata-dioptric telescopes use spherical mirrors and they are very expensive as well. But these Cata-dioptric telescopes use corrector plates to reduce 90% of the aberrations.
Should you buy a Spherical or Parabolic mirror telescope?
As the parabolic mirror has great performance and the images you will see are sharper from these telescopes. If you are buying a telescope that has an aperture size of more than 4-inches, then you should prefer to buy a telescope with a parabolic mirror. You won’t get any aberrations with these telescopes.
If you are buying a small aperture telescope, then the spherical mirror will work as well. There will be much fewer aberrations in small apertures but the images will be good. Make sure the telescope with a spherical mirror has a longer focal length. That’s how these mirrors are different from each other.
Check out other telescope concepts and basics Here.
