Centre of digitization of photographic plates
and reduction of old observations
NAROO (New Astrometric Reduction of Old Observations)

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Purpose of the project:

The old observations of the bodies of the solar system are of great interest: they make possible to better evaluate the dynamics and physical evolution of these bodies. To build the dynamical models of the solar system, observations are necessary to adjust the constants of the motions. For this purpose, observation sampling must be sufficiently extensive to determine the small effects that accumulate over time but are difficult to detect on close observations. Thus, the astrometric observations published at the end of the nineteenth century are still useful and used for the current models.

Unfortunately, these old observations did not benefit from accurate star catalogs for their reduction, and this biased these data. It appeared to us that a new reduction with recent catalogs could improve their accuracy. For this, it was necessary to find the original observation as the photographic plates. A new measurement based on a sub-micrometric digitization of these plates and an advanced image processing could then be used in a new reduction using the latest catalogs of reference stars (UCAC ...).

These modern catalogs did not make possible to go back beyond the 1960s but the tests we carried out thanks to the DAMIAN scanner of the Royal Observatory of Belgium and the arrival of the catalog Gaia whose proper motions will allow to go up to the late nineteenth century justified our approach. A work of inventory and backup of the available plates, of selection of the best old observations and the building of a sub-micrometric scanner for the digitization of the photographic plates allowed our project to start.

A more detailed description is available here.


There are a very large number of photographic plates available in observatories. These have more or less interest according to the information that one is able to draw from it. An important point is the existence of metadata necessary for an efficient exploitation of these plates. Some observatories have carried out inventories of their plates: these inventories are very useful for researchers with a specific scientific need.
Below are some available inventories, more or less precise but giving an idea of ​​the scientific fields covered by the observations thus retained.

- Observatoire de Paris
- Observatoire de la Côte d' Azur, Nice
- U.S. Naval Observatory
- South Africa Observatory
- Sternberg Astronomical Institute
- Pulkovo Observatory
- Observatoire d'Alger
- Astronomical Institute of the Romanian Academy of Sciences
- Shanghai Astronomical Observatory
- Smithonian Astrophysical Observatory
- Observatory of the Romanian Academy, Bucharest
- German astronomical photographic plates and films (APPLAUSE)
- Plates of the observatory of Zvenigorod
- Wide-Field Plate Archive of the University Observatory Jena
- Institute of Astronomy at the Bulgarian Academy of Science

Access to the different services:

Using the scanner Digitization and science Access to digitized plates
-how to scan your plates
-the scanner in Meudon
-Astrometry: asteroids and comets
-Planetology: internal structure of icy satellites
-Spectroscopy: Be stars
-Heritage: Paris observatory

Colloquia and workshops on digitization and analysis of old observations:

- A new reduction of old observations in the Gaia era, NAROO-Gaia workshop, Paris Observatory, June 20-22, 2012
- Astrometry/photometry of the solar system after the Gaia project and Phemu campaigns results, Paris-Meudon CIAS workshop, October 14-18, 2015
- Astroplate: International workshop on scientific use, digitization and preserving astronomical photographic records, Prague, March 14-18, 2016

Documents and bibliographic references:

Documents for the presentation of the NAROO project
-Arlot, Jean-Eudes; Birlan, Mirel; Robert, Vincent: 2016, The Project NAROO (New Astrometric Reduction of Old Observations), in Romanian Astronomical Journal, Vol. 26, No. 1, p.3
-Thouvenin, N.; Arlot, J.-E.; Lainey, V.; Robert, V.: 2014, Digitizations in the GAIA framework: the NAROO project, Astroplate 2014, Proceedings of a conference held in March, 2014 in Prague, Czech Republic. Edited by Linda Mišková and Stanislav Vítek. Published by the Institute of Chemical Technology, Prague, 2014., p.36

Publications related to the digitization of plates
-Robert, V.; de Cuyper, J.-P.; Arlot, J.-E.; de Decker, G.; Guibert, J.; Lainey, V.; Pascu, D.; Winter, L.; Zacharias, N.: 2011, A new astrometric reduction of photographic plates using the DAMIAN digitizer: improving the dynamics of the Jovian system, in Monthly Notices of the Royal Astronomical Society, Volume 415, Issue 1, pp. 701-708.
-de Cuyper, J.-P.; Winter, L.; de Decker, G.; Zacharias, N.; Pascu, D.; Arlot, J.-E.; Robert, V.; Lainey, V.: 2009, New Astrometric Reduction of the USNO Photographic Plates of Planetary Satellites, in Astronomical Data Analysis Software and Systems XVIII ASP Conference Series, Vol. 411, proceedings of the conference held 2-5 November 2008 at Hotel Loews Le Concorde, Québec City, QC, Canada. Edited by David A. Bohlender, Daniel Durand, and Patrick Dowler. San Francisco: Astronomical Society of the Pacific, 2009., p.275

Publications of scientific papers related to NAROO
-Robert, V.; Lainey, V.; Pascu, D.; Pasewaldt, A.; Arlot, J.-E.; De Cuyper, J.-P.; Dehant, V.; Thuillot, W.: 2015, A new astrometric measurement and reduction of USNO photographic observations of Phobos and Deimos: 1967-1997, in Astronomy & Astrophysics, Volume 582, id.A36, 8 pp.
-Robert, V.; Lainey, V.; Pascu, D.; Arlot, J.-E.; De Cuyper, J.-P.; Dehant, V.; Thuillot, W.: 2014, Astrometric observations of Phobos and Deimos during the 1971 opposition of Mars, in Astronomy & Astrophysics, Volume 572, id.A104, 4 pp.
-Robert, Vincent; Pascu, Dan; Lainey, Valéry; Arlot, Jean-Eudes: 2014, Astrometry of natural satellites: improving the dynamics of Mars, Jupiter and Saturn with old observations, in American Astronomical Society, DPS meeting #46, id.418.20
-Lainey, V.; Arlot, J. E.; Robert, V.: 2014, The detection of tidal dissipation among planetary systems with the NAROO project: observing in the past, in European Planetary Science Congress 2014, EPSC Abstracts, Vol. 9, id. EPSC2014-500
-Arlot,J.E., J. Desmars, V. Lainey, V. Robert: 2012, The astrometry of the natural planetary satellites applied to their dynamics before and after Gaia, PSS 73, 66 -Neiner, C.; de Batz, B.; Cochard, F.; Floquet, M.; Mekkas, A.; Desnoux, V.: 2011, The Be Star Spectra (BeSS) Database, AJ 142, 149

Other websites dedicated to photographic plates and to digitization:

- Royal Observatory of Belgium (DAMIAN)
- Shanghai observatory
- Smithonian Astrophysical Observatory (DASCH)
- Pulkovo observatory
- German astronomical photographic plates and films (APPLAUSE)
- Digitization at the Institute of Astronomy and Institute of Mathematics and Informatics of the Bulgarian Academy of Sciences

Scientific partnership:
OCA (Nice, France), USNO (Washington DC, USA), SAI (Moscow, Russia), NAO (Shanghai, China), QMUL (London, UK), AIRA (Bucharest, Romania)
Last update: April 20, 2017
  Contact: naroo (at) imcce.fr