The transit circle of the castle-observatory of Abbadia
Refurbishing the instrument
To re-operate the telescope after 40 years sleeping, a minimum of actions were necessary.
It should be noted that the purpose of the refurbishing was not to return to functioning before 1975,
but only to show observations with modern means allowing everyone to see and understand.
The first action to take was a simple cleaning of the instrument, graduated circles and rollers of bearings.
Then, to allow the observations, it was necessary to have an easy observational process
and a camera to show the images of the transits of stars at the meridian of Hendaye.
The reading system of graduations has been doubled by the installation of a removable coder which "reads" and
returns the height measurement on a computer (made by the engineers of Bordeaux Observatory
which has a meridian transit circle in Floirac). The observation of the stars was done via a viewfinder
installed at the focus of the telescope. This viewfinder is removable because past observers have used
different viewfinders depending on the period. It is therefore easy to replace the viewfinder permanently
exposed by a CCD or CMOS camera that returns the images on a screen visible to all.
Finally, the operation of the opening shutters of the building on the outside has been checked
to allow observation and to protect the instrument from rain.
the shutters designed to protect the instrument.Credit: Abbadia Archives
from left to right, the instrument at the cleaning position,
the removable encoder for pointing and the viewfinder.Credit: JEA