Helmos Observatory

Aristarchos Telescope

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The call for proposals for the observing period August 1- October 31, 2014 has been opened. The deadline for submitting proposals is March 31, 2014.


About Helmos
Helmos Observatory is located on mount Helmos (Aroania) in the Northern Peloponese at an altitude of 2340 m (22˚ 11' 46" East, 37˚ 59' 04" North), 130 km southwest of Athens and about 15 km from the city of Kalavryta. The site is one of the darkest areas in Greece and Europe.
Preliminary seeing (median): 0.7" FWHM (experiments conducted past 2 years)
Clouds: 54% clear, 24% partly clear, 22% cloudy (July - October)
Daily peak temperatures (deg): Jul 18.5, Aug 16.4, Sep 15.3, Oct 15.0 (monthly averages)
Humidity: July 55%, Aug 63%, Sep 50%, Oct 52% (monthly averages)
Wind speed: Max 22 m/s, average 6 m/s, median 5 m/s (July - October)
Wind direction: 70% North to West


Historical Elements

Aristarchos (310 BC - 230 BC) was a mathematician, philosopher and astronomer, sometimes refered to as the Greek Copernicus. He was born on the island of Samos and was the first to propose a heliocentric model of the solar system, a hypothesis violently rejected by colleagues and fellow citizens since it was displacing the Earth from the center of the universe (geocentric model). The latter was largely affected by the ideas of Aristotle and Ptolemy. Aristarchos' model was put aside for almost 18 centuries for many reasons (Big Bang: The Origin of the Universe, Simon Singh, Fourth Estate, 2005) when it was finally revived, developed and fully confirmed by Copernicus and Brahe.

Aristarchos was a copious writer but only one of his works has survived, which is based on a geocentric view of the Cosmos. The title of his treatise was "On the sizes and distances of the Sun and the Moon" and it was published in Oxford in 1688. Using correct geometric arguments, he deduced that the Moon's diameter was one third that of the Earth's, while the Sun's diameter was 20 times that of the Moon, since their apparent angular sizes seen from the Earth were just the same. Although his reasoning was correct, his results were erroneous due to lack of accurate observations. Following Eratosthenes' calculations of the circumference of the Earth, he concluded that the Moon's circumference was 14000 km, its true value being only about 11000 km. The fact that the Sun is larger than the Earth was taken as a mere indication of a heliocentric model.

The work "On a system of the Cosmos" has been ascribed to "Aristarchos". We know via citations in the writings of other scientists that he presented another book in favour of a heliocentric universe, though little evidence can be found about the origin of his ideas on this model.