Abstract
The New Astrometric Reduction of Old Observations (NAROO) center can be found at the Paris Observatory in Meudon, and it is dedicated to the measurement of astrophotographic plates and the analysis of old observations. The NAROO digitizer consists of a granite-based Newport-Microcontrol open-frame air-bearing XY positioning table, a scientific sCMOS camera, and a telecentric optical system. The plate holder assembly is suited for mounting glass plates up to 350 mm squared. The machine positioning stability is better than 15 nm, and its repeatability is better than 40 nm. With real photographic plate data, we were able to produce measurements with an accuracy better than 65 nm. The renewed interest about photographic plates concerns the expansion of the database of transient objects evolving in time, since digitization now makes it possible to measure images with a high level of accuracy and to identify all the available objects. The information extracted from such materials can be of an astrometric, photometric, and spectroscopic nature, when not purely imaging, with consequences in planetology, near-Earth asteroid risk assessment, astrophysical phenomena, and general relativity, to mention but a few. Through our scientific program in the Gaia era, we detail examples of current and upcoming uses for the community. We invite researchers to use our facilities and digitize their collection by answering our call for proposals.
Highlights
This paper introduces the current New Astrometric Reduction of Old Observations (NAROO) digitization center and its hardware, operation, and scientific program
Color-dependent errors due to the atmosphere are refraction and dispersion. These are in the zenith direction, and in the absence of a good distribution of reference star colors in the target field, corrections are made using calibration constants determined through specific calibration plates made with images of star clusters (Pleiades or Praesepe) and valid for any plates made during the same observational season
Most of the detections extend from 1996 until today. Those features are a signature of the solar activity and magnetic field underneath the solar surface, and we know that the behavior of some of them is an indicator of the beginnings of solar flares
Summary
The astrometry, in particular, aims to map and measure objects on the celestial sphere. Since a minimum of two reference stars is needed to produce the spherical equatorial coordinates in right ascension and declination of a Solar System object, this would provide the least accurate result as no account was made of the myriad sources of error. These sources include aberrations due to the telescope optics, its alignment, its drive errors, the plate and emulsion errors, the atmospheric refraction and prismatic effects, biases and misalignments of the plate measuring instrument, and plate modeling errors. We detail which errors could be eliminated thanks to NAROO and Gaia
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