Model II Projector
This ZEISS II Planetarium Projector
was for many years the instrument that operated at the old seat of the Rome Planetarium
in the Octagonal Room at Diocletian’s Baths in Piazza d’Esedra. The optical
projector was constructed by the Zeiss Company from Jena and was at the cutting edge of its era. Rome’s
projector was the thirteenth Zeiss projector installed in the world. The Model
II was the first planetarium projector to be widely distributed throughout the
The instrument was donated by
Germany to Italy as part
of World War One damages. It was positioned in the middle of the Sala and was surrounded by wooden seats.
To one side a bench was placed that held the command panel for the motor, which
was equipped with electrical instruments that had illuminated arrow indicators.
The Octagonal Room had a diameter of 22 metres and its dome rose 19 metres; it
was able to house 387 guests. The model II was made of two 0.5 metre diameter spheres
that were joined by a long three pronged metallic cylinder that was set into a
central socket that allowed for free movement in all directions. The entire projection
apparatus was set on a wheeled framework that did not impede the spheres’
movements. The spheres were equipped with 31 projection lamps to represent the
stars on their very same magnitude, another 11 projected the Via Lacetea (the galaxy) and a further 30
projected star system and the constellation names, the meridians, the ecliptics
of the equator and those of the poles.
The disappearance of the
stars on the horizon was achieved by means of sophisticated diaphragm of shutters
placed on the lenses of the projection apparatus and regulated by lead counter weights.
Inside the connecting cylinder the numerous projectors for the sun, the moon,
Mercury, Venus, Mars, Jupiter and Saturn were positioned. The velocity of
planetary movements was set that a year could run its cycle in seven or three
and a half minutes. The Model II furthermore allowed observers to visualise the
effects of equinox, precession, and changes in terrestrial latitude with complete
representations of the southern hemisphere’s sky as well as the north’s.
The instrument, which is
fully original, has been reassembled but is no longer functional. In 1980 the State
Authority for Heritage decided to close the old planetarium, which had been inaugurated
on 28 October 1928 by Mussolini, to restore the Sala della Minerva to permit it
to become an exhibition hall. On the setting of the old planetarium’s history
the projector was dismantled, packed and delivered to the University of Rome La
Sapienza, which stored it at the Monteporzio
Observatory. In 2000 the university handed over the cases containing the
antique instrument to the Comune di Roma, which reassembled this magnificent
feat of engineering so that it would adorn the entrance of the new Rome
In the world, only two Zeiss
Model II Planetarium Projectors remain, which have had no major modifications: Rome’s projector and a Zeiss II from the original Buhl Planetarium
and Institute of Popular
Science in Pittsburgh,
Buhl Planetarium’s Zeiss II was functional until dismantled and placed in
storage in 2002. The Planetarium of the Royal Observatory of Belgium in Brussels operates a Zeiss
II projector, which was rebuilt after World War II with some refinements.
Additionally, the Osaka (Japan) Science
Museum displays a non-functioning
Zeiss II projector (which had undergone some modifications while in use), the
first planetarium projector in Japan.
Planetarium – 2008 May 20)