Some photographic plates represent astronomical observations which always have a scientific value: digitization and a new reduction and analysis will bring new information for the scientific research. Other plates have a patrimonial interest: rare plates or plates representing subjects other than astronomical objects: instruments now missing were photographed on glass plates. Number of these plates deserve to be digitized and made available to the public. Better, a digitization of high-definition can reveal details that have gone unnoticed before.
The "heritage" plates are described in this document (in french).
Plates were securized as explained in this
document (in french).