A. Omizzolo

Digitization and Scientific Exploitation of the Italian and Vatican Astronomical Plate Archives

There is a widespread interest to digitize the precious information contained in the astronomical plate archives, both for the preservation of their content and for its fast distribution to all interested researchers in order to achieve their better scientific exploitation. This paper presents the first results of our large-scale project to digitize the archive of plates of the Italian Astronomical Observatories and of the Specola Vaticana. Similar systems, composed by commercial flat-bed retro-illuminated scanners plus dedicated personal computers and acquisition and analysis software, have been installed in all participating Institutes. Ad-hoc codes have been developed to acquire the data, to test the suitability of the machines to our scientific needs, and to reduce the digital data in order to extract the astrometric, photometric and spectroscopic content. Two more elements complete the overall project: the provision of high quality BVRI CCD sequences in selected fields with the Campo Imperatore telescopes, and the distribution of the digitized information to all interested researchers via the Web. The methods we have derived in the course of this project have been already applied successfully to plates taken by other Observatories, for instance at Byurakan and at Hamburg.

3C 345: the historical light curve (1967–1990) from the digitized plates of the Asiago Observatory

As part of a large project to digitize the plate archives of the Italian and Vatican Astronomical Observatories, we have already performed the digitization of all available plates of the field of the quasar 3C 345. The plates, approximately 100 in number, were taken with the three telescopes of the Asiago Observatory (122 cm, 182 cm, 67/90 cm Schmidt Telescope) in the period from 1967 to 1990. We present here essentially new data, mostly in the B band, about the variability of 3C 345 and also of four other objects (three quasars – Q1, Q2 and Q3 – and the active galaxy NGC 6212) in the same field, in that period. Beyond the well-known 3C 345 itself, the other three quasars also show variability, with a range of 2.0 mag for Q1 and Q2, and 1 mag for Q3. The low-level variability detected for the nucleus of NGC 6212 is more doubtful, and should be confirmed by linear detector data.