Astronomy... 3. Through the Ages

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/

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