Observations of the Sun have been used for both scientific and religious observations for millennia. Civilisations have used the Sun to keep an accurate count of days, months and years since at least 300BC. while scientists such as Galileo studied the Sun through telescopes to discern some of its characteristics.
At the Chankillo archaeological site in Peru can be found the oldest solar observatory in the Americas, a group of 2.300-year-old structures used to track the motion of the Sun known as the Thirteen Towers. These towers provide a rudimentary solar calendar through which the Sun can be traced.
The towers, each between 75 and 125 square metres (807 and 1.345 square feet) in size, run from north to west along a ridge along a low hill. From an observation point to the west of the ridge the Sun can be seen to rise and set at different points along the ridge, which allowed ancient civilisations to track the number of days it takes the Sun to move from tower to tower.
Much later, in 1612, the renowned Italian astronomer Galileo Galilei (1564-1642) used his telescope to make one of the first observations of sunspots on the surface of the Sun. In 1749 daily observations began at the Zurich Observatory and, since 1849, continuous observations have been made to count the number of sunspots present on the Sun's surface at any one time.
Fast forward to today and, aside from SOHO, one of the primary telescopes used to observe the sun is the Japanese Hinode spacecraft. Hinode is a telescope in sun-synchronous Earth orbit, which allows for nearly continuous observation of the Sun. It was launched on 22 September 2006 and was initially planned as a three-mission study of the magnetic fields of the Sun, but its mission has since been extended as it continues to operate nominally.
Another important Sun-observing telescope is the Solar Dynamics Observatory (SDO). launched by NASA in 2010. The goal of the SDO is to study the influence of the Sun near Earth, predominantly how the Sun's magnetic field is responsible for the solar wind once it is released into the heliosphere. It should help scientists further understand the Sun's influence on the Solar System.
In the future, NASA's Solar Probe Plus will be the closest spacecraft to the Sun, approaching to within just 8.5 solar radii (5.9 million km. 3.67 million miles, 0.04 AU) after its launch in 2018. It will probe the outer corona of the Sun in unprecedented detail, while also becoming the fastest spacecraft of all time in the process at up to 200km per second (120 miles per second).
Apart from million dollar telescopes, many amateur astronomers around the globe today observe the Sun either for entertainment or educational benefit. Using specially designed glasses people can look at the Sun from Earth, although caution must be taken to limit time spent looking at the Sun and it should never be looked at with the naked eye. Other methods of solar observation include using a telescope to produce a trace of the Sun, a method similar to that used by Aristotle and his camera obscura in the 4th Century ВС. Again, precautions must be taken here, as under no circumstances should the Sun be directly observed through a telescope.
Whatever the method, and whatever the mission, observations of the Sun have been a long tradition and will continue to be so for the foreseeable future. Astronomical events such as planetary transits and solar eclipses provide amateur astronomers with opportunities to see extraordinary solar phenomena, while agencies throughout the world will continue to study the Sun and learn more about how the fantastic star works.