Data Extraction from Carte du Ciel Images

Abstract

Carte du Ciel (from French, map of the sky) is a part of a 19th century astronomical project to build a catalogue of coordinates of stars up to 11th magnitude. The data of interest is in the form of digitized astrographic plates where each of them contains three expositions of the same sky section.
Our goal is to design a software tool that would be able to extract automatically data from the digitized astrographic plates. Although created with another purpose, these images contain data for astronomical events, such as stellar explosions. These events can be detected by analyzing triads of stars (referred in the literature as asterisms) that are result of the three expositions of the same star on the same photographical plate. It can be assumed that if a significant difference between the three expositions is detected, an astronomical event is being observed.
This paper examines the image processing and pattern recognition methods that can be adopted for the automatic detection of astronomical events in the Carte du Ciel images.