Prismatic Spectrograph A

Year: 1946
Manufacturer: Officine Galileo – Florence
Materials: aluminum, steel, brass, optical glass
Dimensions: L: 1130 mm. P: 550 mm. H: 1700 mm. Weight: 650 kg

Made in 1946 by the Officine Galileo in Florence, spectrograph A was a precision instrument designed for the Cassegrain focus of the Galileo telescope. With a compact and symmetrical structure to minimize flexures, it can rotate 360°, ensuring flexibility in spectroscopic observations.

The operation is based on a specular slit and a mirror collimator that direct light towards one or more flint glass prisms. Light is refracted and dispersed, forming spectra with different linear dispersions depending on the cameras used. Originally equipped with four cameras, the instrument was expanded with three more in the 60s, improving its capabilities thanks to the addition of an intensifier tube.

The spectrograph allowed high-precision observations thanks to the possibility of calibrating light with a comparison spectrum, using sources such as the iron arc or He-Ar-Ne lamps. No longer in use, it represents, for its time, an example of technical excellence in the history of astronomical instruments.