Last time on Telescopes 101, we had a look at how telescopes work. Today, we'll delve into the colourful history of the telescope, and how astronomers were able to move from studying stars by eye to observing galaxies billions of light years away.
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Astronomy is one of the oldest sciences, with most ancient cultures using the stars for religious, navigation, or timekeeping purposes.
The Babylonians, Indians and Greeks were especially interested in the night sky, recording the positions of the stars and planets, and developing the maths we use today to do so. However, everything changed in Europe in the early 17th century.
A lensmaker by the name of Hans Lippershey submitted a patent in the Netherlands in 1608, detailing a design for using lenses to "[see] things far away as if they were nearby".
The patent was not awarded (since the department thought it was already too well known), but this sparked a wildfire of designs. In particular, a man from Pisa named Galileo Galilei was very intrigued and developed his own instrument.
Until then, these instruments were only used for looking at things on the Earth (known as a spyglass) - Galileo was the first to make a design good enough to see objects in space, and was the first to have the name "telescope".
With the invention of the refracting telescope, Galileo went about discovering phenomena yet unknown to the world - in particular the four brightest moons of Jupiter (Ganymede, Calisto, Europa and Io). To this day, these moons are called the Galilean moons after their discoverer.
The refractor telescope continued to be refined and improved throughout the following decades, especially by the then titans of astronomy Johannes Kepler and Christiaan Huygens.
The first reflector telescope was built by none other than Isaac Newton, from which we get the name "Newtonian telescope".
His design had a small diagonal mirror located halfway up the tube of the telescope. Laurent Cassegrain modified this design, putting a hole in the primary mirror and using a convex secondary mirror to bounce light through the hole to the eyepiece.
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Since then, these basic designs have been further modified in various ways to produce better images with less optical defects, with some such as the "Schmidt-Cassegrain" and "Maksutov-Cassegrain" using large lenses over the front of the telescope to correct some of the light before it hits the primary mirror.
The Ritchey-Chretien telescope, designed around the early 1900s, is perhaps the pinnacle of refining the Cassegrain telescope to give it a wider field of view and has been used in many of the large telescopes today, including the Hubble Space Telescope.
These days, modern telescopes have grown to be enormous behemoths, with mirrors as large as 40 metres in diameter. This is a far cry from Galileo's first design, with an objective of 5 centimetres. Modern telescopes also utilise a variety of extra techniques (such as adaptive optics, to improve the image quality, as the telescope size is no longer the limiting factor in observing space.
- Jonah Hansen is a PhD student specialising in space interferometry at Mount Stromlo Observatory, at the Australian National University.
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