By Dr Martin George
On 7 May we shall celebrate the 100th anniversary of the first regular planetarium show, which was presented in Munich, Germany, on 7 May 1925.
Before the first projection planetariums, other methods were used to simulate the starry sky. The Gottorf Globe, built in the 17th century, had stars and constellation patterns painted on its inside surface. An advance was the Atwood Sphere, which began operation in 1913. It had the stars formed by light shining from outside through holes in the sphere. It is still on display at the Adler Planetarium in Chicago.
It was in the 1910s that the concept of a planetarium projector, to project points of light onto the inside surface of a dome, was developed. The first machine to perform this task was built by the German company Carl Zeiss. It showed the starry sky and the positions of the Sun, Moon and planets on a dome above the audience. It was called the ‘Model 1’, but only two of that design were ever made.
Carl Zeiss have made many more models of planetarium projector. Other companies have also made projectors, including Minolta and Goto, both in Japan. Such projectors, including the Zeiss models, are called ‘optomechanical’ projectors, as the equipment is made up of moving parts.
The 1980s saw the appearance of digital projectors. The first of these projected a starry sky by placing a fisheye lens atop a computer monitor. Since then, digital projection technology has improved immensely, and more and more planetariums use digital projection instead of, or in addition to, a ‘classic’ optomechanical projector.
Today there are over 4000 planetariums around the world, including the Ulverstone Planetarium at Hive, which has a 10-metre-diameter dome.
Hive will celebrate the centenary in three ways. On the evening of 6 May, Principal Astronomer Dr Martin George will present a public talk* at the Gnomon Room in Ulverstone titled ‘A century of planetariums and astronomy’, in which he will highlight the advances in planetariums and many of the important astronomical discoveries that have been made since 1925. On the morning of 7 May from 8am to 10am, visitors to the Seventy Acres Café at Hive will be able to meet with Martin as he informally discusses these great advances, and there will be two extra planetarium shows* that day – at 10.30 am and noon, in addition to the normal show at 2pm.
*See www.hivetasmania.com.au for details.