Tools of the Astronomers
This Page was originally created by Carter N and Veer N. (2020-2021)
What is Astronomy?
Before learning about the different tools of an astronomer, we must first understand what they do. Astronomy is one of the oldest professions in space exploration. Astronomers observe the light that comes from the stars, planetary systems and galaxies. In reality, it will take a vast amount of time for the light to reach us on Earth. By the time the light reaches us on Earth, some of these objects may not exist anymore (Boiko).
Astronomers play the role of understanding the behaviour of matter, study the environments that are only found in space, and discover the particles that occur in these processes.
What is a Telescope?
Telescopes are optical instruments that enhance the image of distant objects, to have a clearer image of these objects (Oxford Learner’s Dictionary).
For astronomers to view space, they must use an instrument called a telescope. Astronomers use 2 different types of telescopes, Light telescopes and radio telescopes (Strobel, 2019).
The first telescopes are thought to be created by Galileo Galilei in 1609. However, the earliest telescopes were invented in 1608 by craftsmen in the Netherlands (Kellermann).
What Are Radio Telescopes?
Radio telescopes reflect radio waves to a house at the antenna. As radio wavelengths are large, the radio dish must have a large surface area (CSIRO).
Radio telescopes collect weak radio light waves, bring the waves to a focus, then amplify them for analysis. Radio telescopes are used to study the radio light coming from stars, galaxies, black holes, and other astronomical objects.
Natural radio waves are extremely weak by the time they reach us on Earth. However, cell phone signals are a billion times more powerful than cosmic waves that radio telescopes detect (CSIRO).
Parts of a Radio Telescope
Radio telescopes, similar to all telescopes, come in all shapes and sizes. Depending on the kind of radio waves they pick up, radio telescopes vary in size. As radio waves are very long and cosmic radio sources being extremely weak, radio telescopes are amongst the largest telescopes in the world (CSIRO).
The antenna on a radio telescope is to collect the incoming radio waves. Some antennas use the radio dish to act like a curved mirror to focus the incoming radio waves (CSIRO).
Parabolic dish antenna scopes are the most versatile and dominant type of radio telescope. The parabolic dish antenna is formed to bounce incoming radio waves to create a focus. To examine the range of a particular wavelength in radio waves, operators select a specific sized funnel, to collect the desired radio waves. These funnels are called feed horns and can be as large as a pickup truck (CSIRO).
The dish surface of a radio telescope determines the number of radio waves the telescope can receive. Many radio telescopes use radio dishes that have a mass of over 300 tonnes! That being said, the larger the radio dish, determines the number of radio waves it can receive (CSIRO).
In single-dish radio telescopes, the diameter of the dish will also determine the field of view that the antenna can receive radio waves (CSIRO).
Many telescopes will spin around a shaft that is aimed toward the North Pole Star. Such equatorial mounts allow the telescopes to follow a position in the sky as the Earth rotates. However, these large equatorially-mounted radio telescopes are extremely difficult to build. Most modern radio telescopes that are built have a digital computer that drives the telescope on a simpler tilt (CSIRO).
To boost weak radio signals, radio telescopes use receivers or amplifiers. These amplifiers are fragile and require coolant to avoid interference between thermal noise (CSIRO).
When receivers are placed at the focus, the detected signal travels along cables with the feed support structure to a point near the ground (CSIRO). The signals are then documented and analyzed using recorders.
Most modern radio telescopes use recorders to document the incoming radio waves (CSIRO). These recordings are then transmitted via fibre optic cables to be stored in a computer disk (CSIRO).
Older radio telescopes must be tuned to specific frequencies to watch for signals molecules of gas in space. In comparison, recent radio telescopes can observe large amounts of frequencies synchronously! Using computers to divide the frequency band, radio telescopes will divide into thousands of separate channels ranging over hundreds of megahertz (Kellermann).
Astronomers use various types of light telescopes to record and document objects in space (Let's Talk Science). Light telescopes have 2 different types of design, the refracting telescope and the reflecting telescope.
Refracting telescopes are long tube-shaped telescopes that use refracting lenses. These lenses refract or bend the incoming light through the tube to the focal point (Lets Talk Science, 2020). Refracting telescopes use 2 types of lenses in the design. The convex lens or large lens will create a focus or a focal point. The larger lens is called the objective lens, and the smaller lens called the eyepiece lens is used for viewing (Las Cumbres Observatory).
The objective lens is the lens that is placed in front of the telescope, that lets light pass through. The eyepiece is the magnifying lens used to view the image that is produced by the objective lens (Lets Talk Science, 2020). However, the light will be refracted at slower speeds depending on the medium (Las Cumbres Observatory).
Index of Refraction
The higher the refraction, the slower the speed of light is travelling through the substance. In a vacuum, the speed of light will stay at 3 x 10^8 m/s (Las Cumbres Observatory).
In a Refracting telescope, the image size is relative to the focal length and the lens size (Las Cumbres Observatory). The longer the focal length, the larger the magnification will be. Furthermore, the projection brightness will be relative to how much light can enter the telescope (Las Cumbres Observatory). The amount of light collected will be proportional to the size of the objective lens or larger lens.
Doubling the lens's diameter will increase the amount of light captured by factors of 4 (Las Cumbres Observatory). Moreover, the brightness of the image is relevant to the amount of light covered in the image. The smaller the area is, the higher intensity the light will be (Las Cumbres Observatory).
Magnification = Focal length of objective lens / Focal length of the eyepiece lens.
Parts of a Refracting Telescope
Refracting telescopes are essentially long tubes with 2 lenses on each end (Refracting Telescope: Definition, Parts & Facts, 2016). The large lens of the telescope is called the objective. The objective lens’ job is to collect light to refract (Refracting Telescope: Definition, Parts & Facts, 2016). The larger the objective lens, the more light will be collected in the image. The smaller lens is called the eyepiece. The eyepiece’s job is to magnify the image (Refracting Telescope: Definition, Parts & Facts, 2016). Using light refraction, the light entering the objective lens will bend and create a focal point. Light will then pass the focal point, entering the eyepiece. The eyepiece will then receive an enlarged projection of the object (Refracting Telescope: Definition, Parts & Facts, 2016).
Limitations of Refracting Lenses
In refracting telescopes, there are image distortions called chromatic aberration (Las Cumbres Observatory). When light passes through lenses, different colours bend through different angles and create a colour distortion. For instance, some objects when looking through refracting telescopes will have a coloured halo surrounding them (Las Cumbres Observatory).
Reflection telescopes are telescopes that use mirrors to magnify images rather than lenses. Reflection telescopes can be used to examine ultraviolet radiation and infrared radiation (Kellermann).
The reflecting telescopes use mirrors rather than lenses to reflect light to the focal point.
In reflecting telescopes, the scope is composed of 2 mirrors, the primary mirror and the secondary mirror (Kellermann). The primary mirror is the curved mirror at the back of the telescope that focuses the light. The secondary mirror is smaller compared to the primary mirror which redirects the light toward your eye (Let's Talk Science, 2020).
Unlike Refracting telescopes, reflection telescopes have multiple advantages over refractors. As reflected light does not disperse according to its wavelength, reflecting telescopes are not subject to chromatic aberration. Furthermore, reflector telescopes can have the same magnification with the same diameter but a shorter telescope tube (Kellermann).
Parts of a Reflecting Telescope
Many parts make up a reflector telescope. Firstly, the tube is a long white part that holds the mirror (Bloch, 2019). The mount is the whole assembly that is in charge of supporting and moving the telescope tube. The eyepiece is a knob for focusing the image and there is a sleeve that you can insert different sized eyepieces (Bloch, 2019). Hidden inside the tube is a primary mirror that gathers all the light, then reflects it toward the eyepiece. The counterweight is a heavyweight that balances out the telescope and makes it easy to maneuver (Bloch, 2019). There is a part that not all telescopes have known as the motor. The motor turns the telescope and rotates one complete revolution every 24 hours (Bloch 2019). This allows you to point the telescope to an object and the motor will automatically follow the object across the sky. The finderscope helps users find objects in the sky (Bloch, 2019).
- Bloch, R. (2019, August 21). The Optics of Telescopes. Retrieved February 2, 2021, from https://letstalkscience.ca/educational-resources/backgrounders/optics-telescopes
- Boiko, A. (n.d.). Who is an astronomer? Retrieved February 1, 2021, from http://www.space-awareness.org/bg/careers/career/who-astronomer/
- CSIRO Australia Telescope National Facility. (2020, November 17). How does a radio telescope work? Retrieved February 1, 2021, from https://www.atnf.csiro.au/outreach/education/pulseatparkes/radiotelescopeintro.html
- Kellermann, K. L. (n.d.). Radio telescope. Retrieved February 1, 2021, from https://www.britannica.com/science/radio-telescope
- Kellermann, K. L. (n.d.). Reflecting telescopes. Retrieved February 1, 2021, from https://www.britannica.com/science/optical-telescope/Reflecting-telescopes
- Las Cumbres Observatory. (n.d.). Refracting Telescopes. Retrieved February 1, 2021, from https://lco.global/spacebook/telescopes/refracting-telescopes/
- Let's Talk Science. (2020, January 30). Optical Telescopes. Retrieved February 1, 2021, from https://letstalkscience.ca/educational-resources/backgrounders/optical-telescopes
- National Radio Astronomy Observatory. (2019, November 27). What are Radio Telescopes? Retrieved February 1, 2021, from https://public.nrao.edu/telescopes/radio-telescopes/
- Oxford Learners Dictionary. (n.d.). Telescope_1 noun - Definition, pictures, pronunciation and usage notes: Oxford Advanced American Dictionary at OxfordLearnersDictionaries.com. Retrieved February 1, 2021, from https://www.oxfordlearnersdictionaries.com/definition/american_english/telescope_1
- Refracting Telescope: Definition, Parts & Facts. (2016, January 3). Retrieved from https://study.com/academy/lesson/refracting-telescope-definition-parts-facts.html.
- Strobel, N. (2019, December 17). Radio Telescopes. Retrieved February 1, 2021, from https://www.astronomynotes.com/telescop/s4.htm