Centre of digitization of photographic plates
and reduction of old observations

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NAROO (New Astrometric Reduction of Old Observations)

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Home page

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Partnership:

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.

Inventories:

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.

Colloquia and workshops on digitization and analysis of old observations:

Documents and bibliographic references:

Other websites dedicated to photographic plates and to digitization: