Today we know what our neighboring worlds look like, we know how beautiful the universe is, we have seen massive supernova explosions and seen the first image of Earth, a black hole. All thanks to the telescope! Undoubtedly, the telescope has become the most widely used instrument in astronomy and astrophysics. Anyone who wants to do research in this area needs a telescope at some point or another. This article is meant to help you know more about this amazing device.
The telescope really helped discover our place in the universe. In the past, captains and even pirates used telescopes with only 4x magnification and a very narrow field of view. However, today’s telescopes are huge telescope chains, capable of observing every corner of the universe. The telescope acts as our enhanced eye and helps us see things that cannot be seen with the naked eye.
The telescope is an indispensable tool for amateur astronomers and lovers of the beauty of the night sky. Photo: PicsWe
Technically, a telescope is an optical device capable of magnifying images of distant objects using a system of spherical glasses and mirrors arranged in a certain order. The term “telescope” generally refers to optical telescopes, but they have undergone major transformations since their creation in the 17th century. As a result, today we have a wide variety of telescopes. Text operates on wavelengths ranging from radio waves to gamma rays. The main purpose of a telescope is to collect the light and radiation emitted by distant objects and focus it into a focal point, where the images can be observed, photographed or examined.
History of telescopes
Hans Lippershey. Photo: Secretsofuniverse.in
The first telescope* was built about 400 years ago, more precisely in 1608, by a Dutch eyeglass manufacturer named Hans Lippershey. Even though Lippershey did not claim the patent, news of the company’s new invention spread like “fire” across Europe. Lippershey’s design essentially consisted of a convex lens and a concave eyepiece. This device is capable of magnifying objects up to 3 times compared to the original scale.
When Galileo Galilei heard of Hans Lippershey’s telescope in 1609, he immediately began designing without even looking at Hans’ equipment. It greatly improved the capacity of the telescope and achieved 20 times magnification. Additionally, Galileo became the first person to point a telescope skyward and discovered Jupiter’s four largest moons in 1610.
Galileo Galilei presented the telescope he built. Source: All About History
Classification of telescopes
There are many types of telescopes. There are also many classifications: based on the arrangement of lenses and mirrors; depending on the type of radiation that the glass receives; depending on the external conditions they can withstand, etc. But there are three basic types of telescopes, source of development of more advanced versions. These three types are:
Refractive telescopes (refractor) – The first telescope to be developed was the refractor. A refracting telescope uses a lens to collect and focus light. Lenses are placed in front of the telescope and light is bent (refracted) as it passes through these lenses. Most people who are starting to learn astronomy will use refractors because they are easy to use and require less maintenance than other types.
Schematic representation of the structure of an astronomical telescope. Photo: reddit.com, HowStuffWorks
Reflecting telescope (reflector) – The reflector uses a mirror to collect and focus light. All celestial bodies are so far apart that the light from them reaching the Earth is parallel rays. Since the light rays are parallel, the mirror of a reflecting telescope is made into a parabolic curve so that the parallel rays of light can be focused to a point. All research telescopes and large amateur telescopes today are reflectors because they have many advantages over refractors.
Schematic representation of the structure of a reflecting telescope. Photo: Liverpool Astronomical Society (LAS)
Complex/composite telescopes (Compound/Catadioptric Telescopes) – Compound telescopes can be considered a “hybrid” between a reflector and a refractor. They combine the best features of both types.
Schematic representation of the structure of a combined telescope. Photo: Abrams Planetarium
Basic terms related to telescopes
Objective (Objective lens) – The lens placed in front is called the objective or primary lens. It collects light from distant objects and focuses it on a point.
Opening (Aperture) – The diameter of the primary mirror/lens is called the aperture (aperture). The larger the aperture, the brighter the resulting image. A good amateur telescope usually has an aperture of 80-300mm. Meanwhile, some large multi-billion dollar professional telescopes have mirror apertures of up to 10 meters.
Focal distance (Focal length) – When it strikes a mirror or passes through a lens, the light is adjusted to focus on a focal point in a more distant plane. The distance between the center of a spherical lens or mirror and its focal point is called the focal length.
Ocular (Ocular) – The eyepiece refers to a small tube containing lenses whose task is to create the final image that the observer can see. Telescopes usually have at least two eyepieces: one for low magnification and one for higher magnification.
Several eyepieces. Photo: stargazerslounge.com
magnifying power (Magnifying Power) – This parameter tells us the ability of the telescope to increase the apparent size of the observed object. Magnification can be determined by dividing the focal length of the telescope (i.e. objective) by the focal length of the eyepiece. Thus, the greater the focal length of the eyepiece, the lower the magnification obtained, but the brighter the image received.
Telescope is translated into Vietnamese as telescope or telescope. In the context of this article, the telescope is called a telescope when it is not used for the purpose of observing the sky. Therefore, when we refer to Hans Premiership’s invention, we use the word “telescope”, and when we refer to Galileo Galilei, we use the word “telescope”.
Earthgrazer – Hanoi Amateur Astronomy Society (HAS)