The Administration building that housed the library at Mount Stromlo Observatory after the January 2003 fire. Image taken by Nick Lomb on 15 November 2004

Over the Easter weekend 2-5 April 2010 the National Convention of Amateur Astronomers (NACAA) was held in Canberra. During the event a well-known amateur astronomer, Colonel Arthur Page, made an important donation to Mount Stromlo Observatory, the library of which was destroyed in the Canberra bushfires of 18 January 2003. The donation was a rare copy of the Catalogue of 7385 stars from Parramatta Observatory. This catalogue is a very significant part of Australia’s scientific history.

The frontispiece of the Parramatta Catalogue – Sydney Observatory copy. Courtesy Powerhouse Museum

Parramatta Observatory has been previously discussed in this blog and is also a theme for the Powerhouse Museum collections database. Beginning observations in 1822, it was the first proper astronomical observatory set up by Europeans on the continent. The catalogue published in England in 1835 represents the major outcome of the observatory’s work.

The transit telescope from Parramatta Observatory was one of the two instruments used to determine the positions of stars for the catalogue. Part of the other instrument, a “mural circle”, can be seen below the transit telescope – the telescope part is now missing. Both objects are on display at Sydney Observatory. Image courtesy Sydney Observatory

The Catalogue of 7385 stars is somewhat controversial as the positions of the listed stars are not as accurate as they should be. Part of the reason is believed to be a problem with the transit telescope (shown on picture above) that the astronomer James Dunlop used for his observations. Another is that for many of his observations he used another instrument called a mural circle in a way that it was not designed to do and was not really capable of doing.

According to the first Government Astronomer at Sydney Observatory, which inherited the instrument from Parramatta Observatory, the problem or problems with the transit telescope were, “the irregularity of its pivots and the weakness of its axis”. A few years ago I asked a colleague from the Conservation Department of the Powerhouse Museum to check the pivots. He reported that, to the accuracy of his measurements the pivots, were round and parallel. However, there was a slight difference in the diameters of the two pivots with one being 2.4752 cm while the other is 2.4778 cm. This 26 micron difference could explain some of the problems experienced with the telescope in the past.

Arthur Page tells me that he purchased the catalogue from an academic who was moving from Sydney to Townsville. He says ” I needed it to trace histories of magnitudes of [the bright variable star] Eta Carinae. Naturally I used it for a heap of other stars (bright stars). I was offered ten times the buying price, but I felt Stromlo deserved my thanks for how they guided me into serious work.” It is a most generous and important gift.

Another copy of the Parramatta Catalogue together with the extant instruments from Parramatta Observatory is on display at Sydney Observatory. The Observatory is open 10 am to 5 pm daily (except Good Friday and Christmas Day) and entry is free.