Astrometry with "Carte du Ciel" plates, San Fernando zone. II. CdC-SF: a precise proper motion catalogue

TL;DR

This paper presents the CdC-SF, a precise proper motion catalogue derived from historic 'Carte du Ciel' plates, covering over half a million stars with high accuracy, extending proper motion data to fainter magnitudes.

Contribution

It introduces a new astrometric catalogue based on digitized historic plates, with developed techniques to handle distortions and precise proper motions for 560,000 stars.

Findings

Catalogue covers 1080 deg² with 560,000 stars.

Positional uncertainty is 0.20 arcseconds.

Proper-motion uncertainty is 2.0 mas/yr.

Abstract

The historic plates of the "Carte du Ciel", an international cooperative project launched in 1887, offer valuable first-epoch material for the determination of absolute proper motions. We present the CdC-SF, an astrometric catalogue of positions and proper motions derived from the "Carte du Ciel" plates of the San Fernando zone, photographic material with a mean epoch of 1901.4 and a limiting magnitude of V~16, covering the declination range of -10deg < declination < -2deg. Digitization has been made using a conventional flatbed scanner. Special techniques have been developed to handle the combination of plate material and the large distortion introduced by the scanner. The equatorial coordinates are on the ICRS defined by Tycho-2, and proper motions are derived using UCAC2 as second-epoch positions. The result is a catalogue with positions and proper motions for 560000 stars, covering 1080 degrees squared. The mean positional uncertainty is 0.20" (0.12" for well-measured stars) and the proper-motion uncertainty is 2.0 mas/yr (1.2 mas/yr for well-measured stars). The proper motion catalogue CdC-SF is effectively a deeper extension of Hipparcos, in terms of proper motions, to a magnitude of 15.