HISTORY OF SOLAR IMAGING

For several thousands of years people have looked up into the sky and wondered about our Sun. For years the Earth was considered the centre of everything until the Copernican heliocentric model was put forward in 1543, although others had tried before him with lesser conviction. Here is a brief history on the discoveries which occurred in order for Solar imagery to be what it is today.

• 28B.C - The first ever recorded observation of sunspots by Chinese astronomers who probably could see the largest groups of spots when the dust filtered the sun's glare in the deserts.

• 800s - The first modern observatory was built in Iraq by Arabic astronomers

• 900s - The first reference to an "observation tube" is found in the work of Albatenius. Though these early observation tubes did not have lenses, they "enabled an observer to focus on a part of the sky by eliminating light interference."

• 1185 - The first record of solar prominences in a Russian chronicle following an eclipse.

• 1605- Johannes Kepler is the first to comment about the Sun's corona, suggesting that it is light reflected from matter around the Sun.

• 1609 - Galileo Galilei builds his first optical refracting telescope. He was one of the first to use the telescope to support the heliocentric theory.

• 1610 - The first view of sunspots through a telescope by several scientists, including Gallelio.

• 1668 - Isaac Newton constructs the first practical reflecting telescope, the Newtonian telescope. Its simple design is still used by amateur telescope makers.

• 1672 - Laurent Cassegrain designs the Cassegrain telescope. The idea has been used since then several times, due to the parabolic primary mirror and a hyperbolic secondary mirror to reflect light back along the line of sight.
  

• 1684 - Christiaan Huygens published "Astroscopia Compendiaria" in which he described the design of very long aerial telescopes. He used his self designed telescope to look at Saturn as well as focusing on stellar groups.

• 1687 - Isaac Newton publishes "Principia", which makes precise long-range eclipse prediction possible.

• 1724 - Giacomo Filippo Maraldi concludes that the corona is part of the Sun because the Moon traverses the corona during an eclipse.

• 1789 - William Herschel finishes a 1.2 m optical reflecting telescope. Throughout his lifetime, Hershel constructed over 400 telescopes.

• 1800 - William Herschel founds science of solar physics by measuring the temperature of various colours in the Sun's spectrum; he detects infrared radiation beyond the visible spectrum

• 1801 - Johann Wilhelm Ritter uses the spectrum of the Sun to establish the existence of ultraviolet radiation.

• 1843 - Heinrich Schwabe , after a 17-year study, discovers the sunspot cycle of 10 years (now known to average 11 years).

• 1845 - First clear photograph of the Sun: a daguerreotype by Hippolyte Fizeau and Leon Foucault.
  

• 1852 - Johann von Lamont , after 15 years of observations, discovers a 10.3-year activity cycle in the Earth's magnetic field, but does not correlate it with the sunspot cycle.

• 1859 - The first observed solar flare on the 1st of September, independently observed by both Carrington and Hogdson.

• 1868 - Janssen and Lockyer discover Helium while observing the spectra of the Sun during a solar eclipse. The prominent yellow line from the spectra observed was unknown at the time and it was assumed it was caused by a solar element, and hence was given its name.

• 1868 - Lockyer was successful in obtaining a spectrum of a solar prominence,

• 1872 - Charles A. Young observes a flare on the Sun with a spectroscope; he calls attention to its coincidence with a magnetic storm on Earth.

• 1892 - George Ellery Hale invents the spectroheliograph, which captures a photo in a single wavelength, giving a monochromatic image. He also discovers the solar vortices and investigates the magnetic fields around sunspots.

• 1904 - George Ellery Hale establishes the first large solar observatory on Mt. Wilson in California.
  

• 1926 - Arthur Eddington proposes that the Sun and stars derive their energy from nuclear reactions at their core.

• 1946 - On the 4th of June, the largest solar prominence ever was observed; reaching a height of 300000 miles from the surface.

• 1951 - Ludwig Biermann discovers the solar wind, a stream of charged gas particles continuously ejected from the Sun in all directions, based on observations of charged gases in comet tails.

• 1959 - Robert Leighton, Robert Noyes, and George Simon discover 5-minute oscillations of the surface of the Sun, leading to the birth of helioseismology.

• 1971 - The first detection of a coronal mass ejection by Tousey using the 7th Orbiting Solar Observatory (OSO -7).

• 1975 - Gerald Smith, Frederick Landauer, and James Janesick use a CCD to observe Uranus, in the first astronomical CCD observation.

• 1980 - NASA's Solar Maximum Mission satellite is launched; It proves that the Sun varies it's energy output.

• 1987 - Eugene Parker proposes that the coronal magnetic field must be continuously reconnecting and releasing energy and that this mechanism can heat the corona.

• 1991 - Japan's Yohkoh spacecraft is launched; It verified, over years of observations, that magnetic reconnection is responsible for coronal mass ejections and flares.

• 1995 - Launch of ESA and NASA satellite SOHO (Solar and Heliospheric Observatory), which lead to the discovery by Gunter Bruckner that coronal mass ejections occur daily.