Dark room

Traditional photografy has been largely used in astrometry for several years, as well in deep sky and comets observations.
With the arrival of CCDs, in 1992, photografy was not completely left abandoned: in fact our dark room has still today all instruments to process efficiently films and pictures.

The film we use is Kodak Technical Pan TP 4415, that normally has a low sensitivity, but that after an hypering process becomes very efficient in most astronomical fields, with low reciprocity and a good response during all the exposure.
The hypering process is a simple treatment that leaves photografic plates in a small camera for twelve hours in an almost pure hydrogen atmosphere at a temperature of 40°C.

Hydrogen is obtained from an acid reaction between hydrogen sulfate and zinc in a Kipp bottle.
Plates are put, one at a time, in a particular plate-holder that stays at the first focus of the telescope of 40 cm. For developing we use an Ornano bath MWP2, for five minutes at 22 degrees °C.

Cooling liquid circulation is obtained by means of a pump connected to an heater exchanger placed in a cell of a refrigerator.
Liquid, at zero degrees, is then pushed up to the dome and circulates inside a small copper pipe surrounding the cooling fins of the CCD ST6.