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


Interest for old observations

Old observations are interesting for modelling transient events or periodic behavior (observable through astrometry for dynamics or through photometry for variable objects.


The first goal of the NAROO project is to make a new astrometric reduction of old observations (especially photographic plates) using the new Gaia reference star catalogue. The figure below shows the accuracy of the proper motions of stars in the Gaia final catalogue. The stars on the plates made one century ago will hace an astrometric accuracy of one mas (depending on the magnitude (G): however, most of the stars observed one century ago are sufficiently bright).

Asteroids and comets

The new astrometric reduction will be fruitful with asteroids and comets observations the accuracy of which being very poor one century ago. This is not the case with planetary systems which were observed with long focus instruments. We will see in the page on planetology which systems are interesting to re-reduce.
The main topics for asteroids and comets are:
- Schmidt plates contain lots of unknown objects detectable thanks to Gaia catalogue
- Old plates will allow pre-discoveries of TNO, comets and NEA/NEO
- A long time interval of observation of such objects will allow to quantify non-gravitational effects.

A Schmidt plate contains thousands objects, among them unknown solar system objects.
The Gaia catalogue associated to a digitization and a new reduction will help us to make pre-discoveries of many objects.

The instruments used for astrometric plates:

Carte du ciel refractor (Paris)       Long focus refractor (Washington DC)                  Schmidt telescope (OCA)
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Last update: April 16, 2017
  Contact: naroo (at) imcce.fr