The telescope in Østervold Observatory dates to 1895 and is a 'double refracting telescope'. The observer looks through the binoculars while images are recorded on 16 centimetre glass plates. Astronomers place the glass plates in the grey tray at the front and use the eyepiece above. (Niels Bohr Institute)

They even found old brass holders used to fix the photographic plates onto the telescope. (Photo: Niels Bohr Institute)

Colleagues Michael Quaade and Johan Fynbo follow with interest as Holger Pedersen presents the historical photographs. (Photo: Niels Bohr Institute)

A collection of glass plates from 1909-1922 show the moon in various phases. (Photo: Niels Bohr Institute)

The photos document a series of important astronomical finds. Among them are a photographic plate from 1912 that shows the giant star Arcturus in the constellation Boötes. Another shows the Orion Nebula. Other finds include an image of the Deneb giant star from the Cygnus constellation taken in 1921, and the Arend-Roland comet visible on the April 26, 1957. (Photo: Niels Bohr Institute)

Pedersen inspects one of the 120-year-old photographic plates. (Photo: Niels Bohr Institute)

Astronomer Holger Pedersen found some cardboard boxes in the basement of the Niels Bohr Institute, Copenhagen, Denmark. The boxes were full of photographic plates that were up to 120 years old. (Photo: Niels Bohr Institute)

Here you see the solar eclipse of 1919, used as evidence for Albert Einstein’s theory of general relativity by the English astronomer Arthur Eddington. (Photo: Niels Bohr Institute)

120-year-old astronomical photos discovered in basement

Retired astronomer unearths photo of 1919 solar eclipse that helped prove Einstein's general theory of relativity.

Oliver Nyberg

tuesday 15. December 2015 - 06:10

The basement under the Niels Bohr Institute in Copenhagen, Denmark, is a treasure trove of forgotten secrets.

It was here, that that retired astronomer, Holger Pedersen, made a surprising find of 120-year-old photographic plates. In among the photos, he found images of Jupiter, double stars, and a historic solar eclipse, according to a press release from the university.

"One day when I went down to the basement to make a cup of tea, I saw some crates from Østervold Observatory. They had been moved there many years ago, when the observatory shut down,” says Pedersen in the press release.

“The crates turned out to be full of cardboard boxes, so I took them up to the office to look at them,” he says.

It was in these boxes that he discovered the rare collection of over 150 photographic plates.

1919 solar eclipse that proved Einstein right

One of the glass plates is particularly interesting to astronomers as it shows the solar eclipse on May 29, 1919, which helped prove Einstein's general theory of relativity.

Einstein put forward the general theory of relativity in 1915. The theory predicts that the Moon's gravity deflects light from distant stars, when the moon passes in front of the sun.

The original photo was taken by the British astronomer Arhtur Eddington in Brazil, in 1919. Whilst the glass plate found in the basement of the Niels Bohr Institute is a copy of the original, it is still considered rare and historically interesting.

Pedersen is now considering seeking funding to get the footage digitized for the Natural History Museum, Denmark.

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Read the Danish version of this story on Videnskab.dk

Translated by: Catherine Jex