Background and early years During the decade of 1930,
Stavros Plakidis, then director of the
National Observatory Athens, made great efforts to relocate the observatory from its central premises in
Thiseio. That location had been selected by
Eduard Schaubert almost a century earlier, when
light pollution still was not very noticeable in
Athens. Plakidis decided that the Koufos hill in
Penteli, on the side of
Mount Pentelicus at an altitude of , was a more suitable location. An important factor was also its proximity to Athens, being about away from the city centre. Plakidis started making observations there in 1936 It was equipped with multiple telescopes and other astronomical and meteorological instruments. However, during the
Axis occupation of Greece in
World War II that started a few years after its establishment, the station was under performing, being used only for the collection of meteorological data and the scarce conducting of astronomical observations. The
Germans requisitioned the Penteli Astronomical Station and erected a communications station on the Koufos hill, which later brought electricity up to the observatory. During the requisition, all the instruments were transferred to the Laboratory of Astronomy of the
National and Kapodistrian University of Athens or to the central premises of the National Observatory of Athens. in which the long collaboration between
Stavros Plakidis and
Arthur Eddington played a crucial role. The construction of a building to house the telescope started in 1957. The telescope was relocated there in 1959 and it was the largest telescope in Greece until 1975, while the observatory is also hosting the
Institute for Environmental Research and Sustainable Development. Both are independent institutes of the National Observatory of Athens. Since September 2000 the Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing is also operating the Athens Digisonde in the location. Four receiving antennas where installed for the creation of an
ionosonde that is studying the Earth's
ionosphere using the
ionospheric sounding technique.
During the 2024 Attica wildfires During the
2024 Attica wilfires part of
Mount Pentelicus was burnt and the fire almost reached the Penteli Observatory. In August, the fire was spreading towards the observatory and the building was evacuated. The flames entered the observatory's yard and they were put out by the firefighters just a few meters away from the main building. == The Newall Telescope ==