Observations

Sydney Observatory in the early 1980s_the basement

Looking south in Sydney Observatory’s basement in about late 1982

Looking south in Sydney Observatory’s basement in about late 1982. Photo Nick Lomb

in July 1982, when Sydney Observatory came under the auspices of the Powerhouse Museum, it looked very different to what it does today. Here are a couple of pictures of the Observatory’s basement before the changes brought about by the Observatory’s new role began in earnest.

In the early 1980s the Observatory’s basement was a magical place housing lots of clocks and related devices that could be both heard and seen. Evening and Wednesday afternoon visitors were taken there to look at two large models – one showed the planets circling the Sun while the other was a model of the Earth and the Moon circling the Sun. Visitors were fascinated by these devices as it is so much easier to understand these motions including the seasons, phases of the Moon and eclipses when looking at three-dimensional models.

In the above photograph the Sun, Earth, Moon model (tellurium) is in the foreground. It was built in the Observatory’s workshop in 1952 and though no longer on display, it remains in the collection of the Powerhouse Museum.

Against the back wall we can see the Shortt 49 slave clock. The Shortt clocks were the most accurate mechanical clocks ever made with a daily accuracy of about 0.01 seconds. They consisted of a master clock, in which the pendulum oscillated in a vacuum, and a slave clock, the pendulum of which was corrected every 30 seconds by the master clock. Sydney Observatory had two of these clocks with both slaves on show in the basement, while the masters were in a separate temperature-controlled room. Incidentally, in those low tech and low budget times, the temperature control consisted of a continuously switched on electric bar heater that had been rewired for low wattage.

The old refrigerator next to the slave clock was used not to store beer or other beverages for the astronomers, but the photographic plates used for photographing the sky. The plates needed to be kept cold before they were exposed.

The boxes on the left housed equipment relating to the clocks. The box at the end was internally lit and had a glass top so that visitors could see the relays that sent out the six-dot signal or the ‘pips’ to radio stations on the hour. The clock that controlled these relays was an atomic clock housed upstairs, but the mechanical clocks in the basement were kept going as part of a complex backup system. On rare occasions the pips were not sent out and immediately the radio stations called and complained. The problem was usually due to a telephone line failure.

Looking north in Sydney Observatory’s basement in about late 1982

Looking north in Sydney Observatory’s basement in about late 1982. Photo Nick Lomb

In the photo above we are looking in the opposite direction and we have a better view of the planet model or orrery that showed the relative rates that the planets move around the Sun, which was represented by an incandescent light globe.

The poor state of the painting on the ceiling is rather obvious. The story was that the Observatory had been hurriedly painted for the 1973 General Assembly of the International Astronomical Union that was held in Sydney with the Government Astronomer Harley Wood as the chair of its organising committee. Somehow the painters made such a mess of the basement ceiling that the paint peeled off soon afterwards.

The room at the end of the basement with light escaping through the glass panel in its door was the temperature-controlled room that housed the two Shortt free-pendulum master clocks. Just to the left of the door with the glass panel is a small dark room used to develop the photographs of the sky taken with the Observatory’s astrographic telescope and its attached camera.

Today, the basement, also known as the Discovery Room, is a lecture room used for adult education classes and by the Sydney City Skywatchers for their monthly meetings. If you have not been to the basement, come along on the first Monday of each month at 6:30pm to a meeting of the Skywatchers. All are welcome and there is only a token payment of $2 requested for supper and a raffle ticket.

2 responses to “Sydney Observatory in the early 1980s_the basement

  • Wow. That bring back memories. I must of spend tens of hours there over the years, and the most memorable thing was the volume of the ticking clocks! The person on the night would take you down there on the hour, where you could set your watch and hear ‘George’ the clock calling out the time or counting the click to reach on the hour. We were repeated told why the room was constantly at temperature.

    The open box on the bottom right I think had a circular disk with the holes punched out. it was something to do with speaking the time, revolving once every minute, if recall correctly.

    I also remember the whirring of the orrery as it accelerated to the movements of the planets around the sun. I remember that the model of Saturn was pretty accurately represented, with the rings tilted to the ecliptic just perfectly, so you could see the changes of the rings.

    It is where I learnt about the geometry of eclipses and the 5.5 degree tilt of the moons’s orbit to the ecliptic – causing eclipses not to occur every new moon or full moon.

    I still remember the first time I went in this room in early March 1971. (I’ll have to look in my first Observing Book, which has the exacted date, but I knew it was a school night. Gosh it brings back memories.

    (Just like my similar memories of my own visits to the Spitzer planetarium in the old Museum in Ultimo, which I use to go on many Saturdays and see the presentations – sometimes twice in a row, waiting usual twenty minutes until its next showing. Again, I use to incessantly quiz the poor fellow the program, with various questions. I still have some of the ol’ paperwork of some star map and of a green paged yearly ephemeris showing the bright planets, Sun and Moon. I also remember I bought a book in the foyer on historical astronomy, with the flasher-look orreries in Europe.)

    Thanks Dr Lomb for bringing back ‘memory lane’!!

    Also I’d come to your meeting, but the old stairs are just a bit difficult for me.

    • Thanks for your comments Andrew. I am sure many other people would have memories of visiting the Observatory and its basement during their school days. Yes, the ticking of the clocks, especially late at night when there were no other sounds, were highly memorable. ‘George’ the talking clock only arrived at the Observatory later on, in the late 1980s after retirement from its duties at the GPO in Martin Place. However, the hourly time signals could be seen as the relays operated in the lit box on the hour. Rotating discs with slots on them were essential components of the time signal system. Levers tracked the circumference of the discs and as the levers dropped into the slots they triggered the operation of the relays that sent out the ‘pips’.

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