A telescope is an optical instrument used to see distant objects’ images, so the object appears nearer and larger. Telescope uses a combination of lenses and mirrors to show a magnified image of distant objects. The emission, absorption, or reflection of electromagnetic radiation helps to observe a magnified image of an object far away from the eyes. Here, we present you the detailed information about telescope types and uses.
The telescope was first invented by Galile. Since then, a revolutionary advancement has been made in the development of the telescope. With a telescope’s help, the astronauts can easily observe space bodies like Moon, stars, and other planets. The telescope allows us to see objects that we can never see with our naked eyes.
The telescope has into two types depending upon the collection of electromagnetic radiation by optical combination. The part of the telescope that collects the electromagnetic radiations is called as “objective.” Based on the objective, the type of telescope is determined.
The two basic types of telescopes are reflecting telescope and refracting telescope.
Among various telescope types and uses, there is a “reflecting telescope”. In this telescope, light rays bounce back when it strikes at a concave surface. The reflecting telescope has a mirror as its objective, which gathers and focuses light. The mirror elongates the focal path of the light. This type of telescope was first introduced by Sir Isaac Newton, and it became popular due to the clear and sharper image. The light rays coming from all the celestial objects are parallel. Duetelescope’s primary mirror to these parallel rays, the primary mirror used in the reflecting telescope, is of a concave or parabolic shape. This concave-shaped mirror lies at the rear of the telescope tube, and the front surface is coated with a thin film of metal.
When the light strikes at the mirror, it is reflected, and the image inverts at the focal plane, which is located at the upper end of the tube. Mostly the reflective telescope consists of a smaller secondary mirror, which is located in front of the large primary mirror. The secondary mirror reflects the light to a more suitable viewing point.
Most reflector telescopes have a smaller secondary mirror in front of the large primary mirror. The reflecting telescope can examine the visible region in the electromagnetic spectrum. It is used to study both the regions of shorter and longer wavelength adjacent to it, such as ultraviolet and infrared rays.
A contemporary of Sir Isaac Newton named Laurent Cassegrain invented a new type of reflective telescope – Cassegrain telescope. This optical instrument consisted of a small convex mirror. This bounces back the light through a small hole located in the primary mirror to a focus located behind the primary mirror. Nowadays, the reflecting telescope that is largely in use consists of a cage located at the primary focus. So, while operating, the observer can sit inside the telescope tube.
Light changes its direction at an angle when it passes through one medium to another. This bending of light at an angle is refraction. As the name refers, this type of telescope is based on the phenomenon of refraction. The refractor telescope has a lens as an objective. The lens is a piece of glass that bends the light that passes through it. Light rays, when strikes at the lens, bend at an angle, producing the image. So there is a combination of lenses in refracting telescope to obtain a magnified image of a distant object. Only two lenses are there in a simple refractive telescope. One is the objective, and the other the eyepiece.
By refracting light rays, the objective lens produces an image at its focus. Then the eyepiece magnifies the image. The selection of eyepiece depends upon magnification. Want to get the best refracting telescope? Wait no more!
If you want to study the moon, you need an eyepiece of high magnification. If you want to study a star, you need an eyepiece of low magnification. The powerful eyepiece has a smaller focal length, and the low magnification eyepiece has a larger focal length.
Reflecting vs. refracting telescope
People often get confused when it comes to the competition between reflecting vs. refracting telescope. While talking about different telescope types and uses, it is important to discuss a direct comparison. Modern research proves that the reflective telescope is more common than the refracting telescope. The reason behind the more widespread usage of reflecting telescope is its advantages over the refractive telescope. The reflecting telescope is not subject to chromatic aberration. In contrast, the refractive telescope is subject to chromatic aberration. This is because the refracted light disappears according to wavelength. Whereas, the reflected light does not.
The reflector telescope consists of a short tube, so it is cheaper than the refractive telescope, which has a longer tube, but the diameter remains the same. Also, mostly reflecting telescopes are smaller; consequently, the construction is also inexpensive. The reflective telescope can not make the passage of ultraviolet rays because it consists of lenses. Ultraviolet rays cannot be passed through lenses. Also, the light can pass through a refractive telescope only if the lens is thinner. Another weak point of a refractive telescope is that its glass lenses always have some imperfections. One of them is an imperfect curvature on both sides of the lens.
Now there are also few plus points of the refractive telescope over the reflective telescope. The refractive telescope’s surface rarely needs cleaning as inside the tube. This helps to block the glass surface from the atmosphere. Due to this, there is no effect of the atmospheric change on the telescope tube. Hence, the image formed by it is much sharper and clearer than that of a reflective telescope. Also, the optical system of the refractive telescopes is more resistant to misalignment after the initial alignment.
Due to the revolutionary inventions of different types of telescope, astonishing discoveries have been made in the field of astronomy.