Hamburg Observatory completes APPLAUSE project

14 October 2022
International research network digitises historical astronomy images with AI and University of Hamburg

Researchers across the globe can now access some 94,000 digitised photographic plates from observatories in Germany, Estonia and the Vatican. This comes after researchers at the University of Hamburg and a network consisting of the Leibniz Institute for Astrophysics Potsdam, the Friedrich Alexander University Erlangen-Nuremberg and the University of Tartu in Estonia digitised high-resolution astronomical images as part of the Archives of Photographic Plates for Astronomical Use (APPLAUSE) project. 

Unlocking phenomena from almost 4.5 billion light sources

The catalogue details the time and date of the image, the section of sky and its geographical location. Launched in 2012, and funded by the German Research Foundation, APPLAUSE has generated, calibrated and published almost 4.5 billion light sources from digitised photographic plates. Phenomena in the sky such as brightness and and how the movement of stars have evolved over time, can now be studied. "Of course, the precision of the images (taken in 2012) is not comparable to today's modern measuring methods, but the accuracy of the digitised photographic plates would have been absolutely unimaginable when they were made," according to Dr Detlef Groote, who led the project at the Hamburg Observatory of the University of Hamburg.

Use of artificial intelligence for improved quality

The researchers had developed an open-source programme named Ply Plate with artificial intelligence to conduct the project. Machine learning methods were used to detect and remove defects such as dust and scratches from the plates.  AI facilitated the accurate calibration of the digitised data and assigning it to celestial co-ordinates. The procedure has improved the quality of the data significantly and made the measured data comparable and usable for scientific studies, according to the University of Hamburg.

Hamburg Observatory digitises huge amounts of data

The Hamburg Observatory has scanned historical images and linked photographic plates to metadata and stored them in a database since 2010. However, scanning such huge amounts of data proved time-consuming. "I estimated that it would take me 20 to 30 years just to scan about 35,000 photographic plates in various sizes," said Groote. Thanks to APPLAUSE, key stellar information has now been made available far earlier and in better quality. 


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