Astronomy for GCSE






Astronomy... 3. Through the Ages

In this section:
Page 1:
  • Aristotle
  • Eratosthenes
  • Aristarchus
  • Hipparchus
  • Ptolemy
  • Caliph Al-Mamun
  • Ulugh Beigh
  • Mikolaj Kopernik
  • Giordano Bruno
  • Tycho Brahe
  • Johannes Kepler
  • Galileo Galilei
  • Sir Isaac Newton
This page:
  • Robert Hooke
  • John Flamsteed
  • Edmond Halley
  • Christopher Wren
  • John Gadbury
  • William Lilly
  • Jeremiah Horrocks
  • Giovanni Cassini
  • Ole Rømer
  • William Herschel
  • John Herschel
  • John Goodricke
  • John Couch Adams
  • Urbain Le Verrier
  • Lick Observatory
Page 3:
  • Meudon Observatory
  • Yerkes Observatory
  • Mount Wilson
  • Observatory
  • Edwin Hubble
  • George Ellery Hale
  • Royal Observatory
  • Siding Spring
  • Mauna Kea
  • Cerro Tololo Inter-American Observatory
  • Kitt Peak
  • BTA-6
  • Mstislav Keldysh

Page 4:

  • Whipple Observatory
  • Wyoming Infrared Observatory
  • United Kingdom Infra-red Telescope
  • Thirty Meter Telescope
  • Karl Jansky
  • Jodrell Bank
  • Five-hundred-meter Aperture Spherical Telescope
  • RATAN-600
  • and more

"Other brilliant astronomers of the time [were], notably Robert Hooke, John Flamsteed, Edmond Halley and Christopher Wren."

Of Robert Hooke, he was, in using a microscope, the first to visualise a micro-organism.

I find this curious entry on Wikipedia:

Hooke and Isaac Newton disputed over credit for certain breakthroughs in physical science, including gravitation, astronomy, and optics. After Hooke's death, Newton questioned his legacy. And as the Royal Society's president, Newton allegedly destroyed or failed to preserve the only known portrait of Hooke.

John Flamsteed FRS (19 August 1646 – 31 December 1719) was an English astronomer and the first Astronomer Royal. His main achievements were the preparation of a 3,000-star catalogue, Catalogus Britannicus, and a star atlas called Atlas Coelestis, both published posthumously. He also made the first recorded observations of Uranus, although he mistakenly catalogued it as a star, and he laid the foundation stone for the Royal Greenwich Observatory. - Wikipedia

Wikipedia goes on to say that "[Flamsteed] associated himself with local gentlemen interested in astronomy, including William Litchford, whose library included the work of the astrologer John Gadbury which included astronomical tables by Jeremiah Horrocks... Flamsteed was greatly impressed (as Isaac Newton had been) by the work of Horrocks."

John Gadbury (not mentioned in the GCSE book) was (according to Wikipedia) "an English astrologer, and a prolific writer of almanacs and on other related topics. [He was initially] a follower or disciple, and a defender ... of William Lilly, [but] he eventually turned against Lilly and denounced him in 1675 as fraudulent."

William Lilly was a seventeenth century English astrologer, "described as having been a genius at something 'that modern mainstream opinion has since decided cannot be done at all' having developed his stature as the most important astrologer in England through his social and political connections as well as going on to have an indelible impact on the future course of Western astrological tradition."

He wrote about the 1666 Great Fire of London and was thus brought before the committee investigating the cause of the fire as being suspected of involvement because of his publication of images, 15 years earlier, which depicted a city in flames surrounded by coffins.

Lilly was a controversial character who was both aided and abetted by powerful friends and enemies. He attracted the attention of many members of Parliament, including Lord Keeper of the Great Seal of England, (to whom he dedicated his Christian Astrology), but also accused Members of Parliament of engineering charges against him in 1651. To his supporters he was an 'English Merlin"; to his detractors he was a "juggling wizard and impostor'.

Returning to John Gadbury, his 1652 work Philastrogus Knavery Epitomized was a reply to Lillies 'Ape Whipt' by the pseudonymous Philastrogus, defending Lilly, Nicholas Culpeper and others.

His father William was an estate worker for Sir John Curson of Waterperry House near Wheatley, Oxfordshire, who eloped with Frances, a daughter of the house, a year before John's birth. However, John Gadbury persuaded his grandfather Sir John to put him through Oxford, before his astrological training.

Jeremiah Horrocks (1618 – 3 January 1641), aka Jeremiah Horrox, was an English astronomer. He was the first person to demonstrate that the Moon moved around the Earth in an elliptical orbit; and he was the only person to predict the transit of Venus of 1639, an event which he and his friend William Crabtree (it is said) were the only two people to observe and record.

Horrocks studied (amongst others) the works of Johannes Kepler, Tycho Brahe. Once committed to the study of astronomy, he began to collect astronomical books and equipment and by 1638 he owned the best telescope he could find.

Apparently he helped with the family business by day and, in return, the watchmakers in his family supported his vocation by assisting in the design and construction of instruments to study the stars at night.

Horrocks owned a three-foot radius astronomicus – a cross staff [aka Jacob's staff] with movable sights used to measure the angle between two stars – but by January 1637 he had reached the limitations of this instrument and so built a larger and higher precision version. While a youth he read most of the astronomical treatises of his day and marked their weaknesses; by the age of seventeen he was suggesting new lines of research.

Returning to the book... it says, "There were other great astronomers living in Europe at the same time. For instance Ole Rømer of Denmark (right) measured the velocity, and Giovanni Cassini, an Italian.... made a series of telescopic discoveries, including the main gap in Saturn's rings [which I know to be called the Cassini Division... many more 'divisions' have been identified and named].

"Ole Rømer first demonstrated in 1676 that light travels at a finite speed (non-instantaneously) by studying the apparent motion of Jupiter's moon Io." - Wikipedia, and here.

William Herschel was born in Hanover, but came to England while still a young man. When he became interested in astronomy he decided to make his own telescopes. With one of these, in 1781, he discovered a new planet, now known as Uranus [which] moves round the Sun far beyond the orbit of Saturn, the most remote planet known* in ancient times, and it is barely visible with the naked eye.

*I suppose it would be more accurate to say that Herschel identified (what we call) Uranus as a planet. Indeed...

Like the classical planets, Uranus is visible to the naked eye, but it was never recognised as a planet by ancient observers because of its dimness and slow orbit. Sir William Herschel first observed Uranus on 13 March 1781, leading to its discovery as a planet, expanding the known boundaries of the Solar System for the first time in history and making Uranus the first planet classified as such with the aid of a telescope.


Its name is a reference to the Greek god of the sky, Uranus, who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of Cronus (Saturn)... Wikipedia

Also, "Herschel's early observational work soon focused on the search for pairs of stars* that were very close together visually... [He discovered and catalogued] thousands of double stars, star clusters, and the dim, misty patches we call nebulae, some of which are clouds of gas and dust while others are now known to be galaxies in their own right... [Although] some of his ideas sound strange today [such as believing] that the habitability of the Moon [by alien creatures?] was 'an absolute certainty', and he even thought there were intelligent beings living in a cool region below the brilliant surface of the Sun!"

*It seems to me that the ancient Egyptians were interested in binary stars also [as mentioned above (see here)].

Incidentally, the astrological symbol for planet Uranus    features the capital initial letter of Herschel's surname.

It is said (on p.15) that William's son John (also an astronomer, [left]), coined the word 'photography' (more on this in a moment). He achieved (his own) fame by travelling to the Cape of Good Hope between 1833 and 1838 and [made] the first systematic survey of the far-southern stars which never rise over Europe... He also named four of the moons of his father's-discovered Uranus... Amongst his other observations during [the] time [of his visit to the Cape of Good Hope] was that of the return of Comet Halley. [link].

John Goodricke of York... made some remarkable discoveries in connection with variable stars; he suggested, quite correctly, that some stars which change in light, such as the 'Demon Star' Algol in Perseus [again, of interest to the ancient Egyptians], are not truly variable at all, but are binary systems in which one member of the pair is brighter than the other - so that when the fainter star passes in front of the brighter, the total brilliancy, as seen from the Earth, drops."

In 1845 the third Earl of Rosse... built what was then much the largest telescope ever made... a reflector with a 183-cm mirror, and it was set up at Birr Castle, Ireland... [With] a very limited view of the sky (it was mounted between two massive stone walls)... but worked well, and with is Lord Rosse discovered that some of the dim, misty objects catalogued by Messier and (William) Herschel were spiral in form... It was almost eighty years before it could be shown that the spirals are independent galaxies, millions of light-years away.

Source and related article [here]

Returning for a moment the topic of Uranus, for it had been wandering away from its predicted path; clearly some force was pulling it out of position, and, in 1846, two mathematicians, John Couch Adams (England) and Urbain Le Verrier (France), independently decided that the disturbing force must be due to an unknown planet moving still further out from the Sun. The calculated where this planet should be, and, sure enough, the world we now call Neptune was found...

[John Couch Adams] also did much important work on gravitational astronomy and terrestrial magnetism. He was particularly adept at fine numerical calculations, often making substantial revisions to the contributions of his predecessors. However, he was "extraordinarily uncompetitive, reluctant to publish imperfect work to stimulate debate or claim priority, averse to correspondence about it, and forgetful in practical matters". It has been suggested that these are symptoms of Asperger syndrome which would also be consistent with the "repetitive behaviours and restricted interests" necessary to perform the Neptune calculations... - Wikipedia

Le Verrier seems to have attempted a similar application regarding the planet Mercury...

[He] began studying the motion of Mercury as early as 1843... [And in] 1859 [he] was the first to report that the slow precession of Mercury’s orbit around the Sun could not be completely explained by Newtonian mechanics and perturbations by the known planets. He suggested, among possible explanations, that another planet (or perhaps, instead, a series of smaller 'corpuscules') might exist in an orbit even closer to the Sun than that of Mercury, to account for this perturbation. (Other explanations considered included a slight oblateness of the Sun.) The success of the search for Neptune based on its perturbations of the orbit of Uranus led astronomers to place some faith in this possible explanation, and the hypothetical planet was even named Vulcan. However, no such planet was ever found, and the anomalous precession was eventually explained by general relativity theory. - Wikipedia

Now we turn more to the topic of telescopes...

"Towards the end of the [last] century, various large telescopes were built both in Europe and in America. Most of them were refractors, collecting their light by means of large lenses... Among them were the Lick Observatory in California, the Meudon in France, and one at Yerkes Observatory, not far from Chicago..."

Next [adapted from Wikipedia],

"The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California, United States. The MWO is located on Mount Wilson... The observatory contains two historically important telescopes: the 100-inch (2.5 m) Hooker telescope, which was the largest aperture telescope in the world from its completion in 1917 to 1949, and the 60-inch telescope which was the largest operational telescope in the world when it was completed in 1908. It also contains the Snow solar telescope completed in 1905, the 60 foot (18 m) solar tower completed in 1908, the 150 foot (46 m) solar tower completed in 1912, and the CHARA array, built by Georgia State University, which became fully operational in 2004 and was the largest optical interferometer in the world at its completion."


The mirror being delivered in 1917 for the Hooker Telescope.

"By the 1980s, the focus of astronomy research had turned to deep space observation, which required darker skies than what could be found in the Los Angeles area, due to the ever-increasing problem of light pollution. In 1989 ... the 2.5-meter telescope was deactivated, but it was restarted in 1992 and in 1995 it was outfitted with a visible light adaptive optics system...

As the use of the telescope for scientific work diminished again, a decision was made to convert it to use for visual observing. [A] conversion completed in 2014, [and] the 2.5 meter telescope began its new life as the world's largest telescope dedicated to public use."

It was with the Hooker 100-inch reflector, in 1923, that Edwin Hubble made the observations that proved that the spirals and other 'starry nebulae' really are external galaxies rather than mere parts of our own Milky Way.

George Ellery Hale (1868-1938) was a solar astronomer and was a leader/key figure in the planning or construction of several world-leading telescopes. One of these was the one at Yerkes mentioned above. He also made plans for the even larger reflector telescope at Palomar Mountain, California; named Hale after him. It came into use in 1948 and revolutionised astronomy and remained in a class of its own for many years.

Halley's Comet upcoming 1986 approach to the Sun was first detected (in 1982) using this telescope equipped with a CCD camera. In 1997 two of Uranus' moons were discovered bringing the planet's known moon to 17 at that time (27 are now known). Further observations and research can be read about here.

Light pollution, as affecting the Mount Wilson Observatory, was also causing a problem for the Royal Observatory in London (known as the 'timekeeping centre' of the world) and in the 1950s it was temporarily moved 44 miles (70 km) south-east and renamed the Royal Greenwich Observatory. The observatory moved again in 1990, leaving behind some of its telescopes as seen below.

Former Royal Greenwich Observatory, Herstmonceux, East Sussex (2012)

The Observatory's move to Hestermonceux proved to be less than idea and in 1983 the Isaac Newton Telescope (INT) was moved to La Palma in the Canary Islands (a move which proved more costly than building a new telescope on site).

The INT, from England to the Canary Islands

This telescope has since been joined by the even larger William Herschel Telescope (WHT) and the site, Roque de los Muchachos Observatory (ORM), is a multinational affair with many other telescopes and operated by various nations. See International Astronomical Union (IAU).

"All of the first major observatories were in the northern hemisphere. However, many of the most interesting objects in the sky lie in the far south, so that from Europe and the United States they never rise. For this reason there has been a policy of setting up most of the new large observatories in the southern hemisphere."

One such telescope has been the Anglo-Australian Telescope (AAT) at Siding Spring Mountain/Mount Woorat in New South Wales, Australia.

There are now over 60 telescopes at the site, including the UK Schmidt Telescope (UKST), although not all are operational. This Observatory is also a multinational affair. It has not been without issue though; in 2013 three buildings at the site were destroyed by bushfire, although measures in place helped to protect the telescopes themselves. The conflagration however destroyed 80% of the adjacent Warrumbungle National Park.

A view from within Warrumbungle National Park in 1995.

Also in the southern hemisphere is Hawaii and the summit of the dormant volcano Mauna Kea which has become an astronomical centre. However this has not been without opposition; the site being sacred to the Hawaiian religion as the home of several deities. Environmental groups and activists have (also) been expressing concern over endangered species habitat. Developments have continued however, although the gods perhaps expressed themselves in 2006 when a number of the telescopes sustained minor damage from an earthquake and aftershocks.

Mauna mountain as seen from Mauna Loa Observatory

There are numerous observatories in Chile, the most famous being the Cerro Tololo Inter-American Observatory (CTIO).

"In May 1985, Chilean astronomer Arturo Gomez discovered a fuzzy bun-shaped object on a plate taken by the CTIO (Tololo) 1.5 meter telescope. After some investigation, the object was identified as a proto-planetary nebula, a gas cloud emitted by a Sun-like star just after its central hydrogen fuel has all been fused to helium. Gomez's Hamburger is on its way to becoming a full-fledged planetary nebula in a few thousand years." - link

In the United States is Kitt Peak in Arizona. Founded in 1958 it now has more than twenty optical and two radio telescopes and is one of the largest gatherings of astronomical instruments in the northern hemisphere. It was once home to what was the largest solar telescope in the world.

In 1976 the Mayall Telescope at the site was used to discover methane ice on Pluto, and in 2000 the Spacewatch telescope was used to discover the large trans-Neptunuan object in the Kuiper belt, 20000 Varuna. It is named after the Hindu deity Varuna, one of the oldest deities mentioned in the Vedic texts.

BTA-6 is an optical telescope with a 600-cm mirror constructed and installed in the Soviet Union in 1975. When brought into use it was the largest in the world until 1990. It pioneered the technique, now standard in large astronomical telescopes, or using an altazimuth mount with a computer-conrolled derotator. Its name is literally "Large Altazimuth Telescope" or Большой Телескоп Альт-азимутальный / Bolshoi Teleskop Alt-azimutalnyi.

For a variety of reasons, however, BTA-6 has never been able to operate near its theoretical limits; early problems with the mirror (this being the second due to the first suffering cracks and bubbles in the annealing process) were never fully eliminated, the location was also less than ideal. The telescope also suffers from serious thermal expansion problems due to the large thermal mass of the mirror. Upgrades are still ongoing to this day.

One of BTA-6's advocates was Mstislav Keldysh (1911-78) a Soviet scientist in the field of mathematics and mechanics and also a key figure behind the Soviet space program.

Inside the main observatory at BTA-6/

Obviously large mirrors pose problems. The modern trend is to use mirrors made in segments which can be fitted together to produce the correct optical curve. An example was at the Whipple Observatory on Mount Hopkins in Arizona, USA, in the form of the MMT (Multiple Mirror Telescope) Observatory which had six 183-cm mirrors operating together, making a telescope equivalent to a single 442-cm. However, due to improved mirror technology the smaller mirrors were replaced in 2000 with a single large mirror (the telescope kept its original name).

The MMT in 1981 showing its six primary mirrors.

Another major development has been the "Electronic Revolution"; just as the photographic plate replaced the human eye over a century ago, CCDs (Charge-Couple Devices) have now superseded those. No longer does an astronomer have to stare for hours at photographic plates in the dome; everything is computerised - the observer can be anywhere in the world.

Moving on to the topic of 'invisible astronomy'...

William Herschel (previously mentioned) was the first to prove that the Sun sends out infra-red radiation as well as visible light, and now infra-red astronomy is highly important. It is essential to observe from high altitudes because much of the infra-red radiation is blocked out by the Earth's air, particularly by water-vapour content. Thus we have such infra-red telescopes as the Wyoming Infrared Observatory (the largest functional such telescope from 1977 to around 1980) and, the United Kingdom Infra-red Telescope (UKIRT) which is on the summit of Mauna Kea, Hawaii and now funded by NASA. This one is set to be replaced the Thirty Meter Telescope (TMT) which is designed for near-ultraviolet to mid-infrared observations, although progress has been hampered by those 'Mauna Kea' oppositions mentioned above.

A computer/artistic rendering of the TMT.

Radio astronomy began in 1931 when an American radio engineer, Karl Jansky, using an improvised aerial to study 'static' found he was picking up long-wavelength radiations from the Milky Way.

"Who has not heard of the Jodrell Bank radio telescope in Cheshire, England?" asks Patrick Moore. Or the now destroyed Arecibo radio telescope in Puerto Rico (featured in my Einstein@home section)? The former is now named the Lovell Telescope in honour of its creator, Sir Bernard Lovell (1913-2012). The world's largest 'filled-aperture radio telescope' is the Five-hundred-meter Aperture Spherical Telescope (FAST) (五百米口径球面射电望远镜) in China, nicknamed Tianyan (below).

My photograph, taken in 2016, of Jodrell Bank

The largest 'sparsely-filled radio telescope' is RATAN-600 in Russia. In 2015 it dected a strong signal that closely matched what would be expected for a distant source and a SETI candidate and unusual for a natural source. However, the same artificial appearance also makes a terrestrial source likely, such as from a military satellite, secret/reconnaissance, or from a faulty satellite in a slow spin. Other observatories have failed to corroborate the signal.


In 1957 came the start of the Space Age with the launch of Sputnik 1. Since then there have been thousands of satellites and probes launched. We have the Hubble Space Telescope (HTT) launched in 1990, a 239-cm reflector, which has revolutionised our outlook. We have X-ray telescopes, and others that carry out their work entirely above the screening layers of our air.

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