Sydney Meridian Walk


Sydney Meridian Walk is a project created for ‘Boundless – out of time’, Lily Hibberd’s month-long artist and research residency at Sydney Observatory commissioned by the 22nd Biennale of Sydney "NIRIN" and Powerhouse Museum. As an archive of the virtual performance of this walk, Lily created a 24-part blog series for the Sydney Observatory "Observations" webpage.

Presented by Powerhouse Museum as part of the 22nd Biennale of Sydney: NIRIN 2020.

This project was supported by the Australian Government through the Australia Council for the Arts, its arts funding and advisory body.

Remapping Sydney Meridian

Over these next 24 posts we retrace a path of what is known as the Meridian of Sydney. This virtual walk will carry us through plural dimensions of time, past and present, as well as space. Along the way, you will be given the directions for this walk as well as fictions, assumptions and random observations about the establishment of time and its measure in colonial Australia. But how did this project begin?

When I first visited the Observatory in November 2019, one odd feature of the Observatory stood out. Look at the photo above. On the roof, there are two slots. But since there is only one meridian telescope, there should only be one opening. This oddity made me wonder: was the meridian as fixed as they say, or had it moved? This question launched a fascinating investigation, which inspired this blog.

Each day we visit a ‘station’ along the line on a path southward from the Observatory, following the Sydney Meridian. While the stations retrace the Observatory’s ‘prime’ Meridian, like the line itself, the stations are imaginary, approximating the path of the line emanating from the Observatory’s Transit Telescope. But the locations shown on Google Earth along the walk are real, as you can see in the map.

This map provides a guide to the location of each station on this walk. To orient yourself, follow my notes and the coordinates on each post from Station 1 to 24.

For each station there is a poster, which provides clues and historical references for the story of Sydney Meridian. There are also two sets of coordinates. The first of these in black indicates the location of the ‘original’ Meridian, while the one above it in white is the location of the station according to Google Earth on that given day. As we will see, the line is not quite so fixed after all, because these markers, along with the Meridian, are shifting in relation to our changing planet.

Sometimes you will also see symbols and marks on these posters. These are the scars made on boundary reference trees by government surveyors as they staked out land parcels all over the city, triangulated from the Meridian to define the boundaries of each property. Sydney’s early colonial cityscape would have been marked by these trigonometric survey markers in the landscape – vanished long ago.

We have 24 stations ahead. Let's begin with the first, inside the Observatory’s Transit Room.

Station 1

Sydney Observatory Transit Circle Telescope

June 8, 2020

On the ground floor inside Sydney Observatory, in front of the Sydney Observatory Transit Telescope, we stand at the origin of Sydney Meridian. This is Station 1.

I’m guessing you want to know how a meridian is made? In astronomical terms, put simply, it is an arc drawn through an imaginary ‘great’ circle that passes through the two celestial poles: north-south, its counterpart being east-west.

When correlated to a point on the Earth, a meridian is not only an ‘invisible’ line but also one that is arbitrary, because it is an arc that could be drawn anywhere over a terrestrial (earth) or celestial (sky) sphere. The first and only line will always be a ‘prime’ meridian – a ‘zero’ in space and time. But if you want to know the relative location of a meridian around the planet you need two measures to provide you with your ‘longitude’.

First of all you need to calculate ‘midday’. But this is an ancient skill. If we look directly above us at solar noon, we will be midway between sunrise and sunset on that particular spot. The Sun also crosses overhead on the celestial meridian at the same time. The word itself is revealing: meridian comes from the Latin meridies, meaning ‘midday’, and this is where the term ‘a.m.’ (ante meridiem) and ‘p.m.’ (post meridiem) come from.

Figure 1. Image of Sydney Observatory Transit Telescope from Google Earth.

To determine the longitude of a place you need not only to know the time but also to what time it is at a place of reference, called a ‘prime’ meridian. To do this, even over a few metres, requires a portable and accurate clock that keeps ‘standard time’ of that prime location – the most renowned of these being Greenwich Mean Time.

The problem of longitude was one of the most challenging questions for navigation and thus for colonisation in the mid-18th century. It was invention of the marine chronometer (such as the E520, which Matthew Flinders used to circumnavigate and chart Australia from 1801 to 1803) that provided the means for the British to reliably navigate the planet, and facilitate its program of colonising Australia.

When it comes to determining a reference or prime meridian on land, the counterpart to the chronometer is the transit telescope. From the early 17th century, largely thanks to the work of Galileo Galilei, the capacity to both view and track the stars was transformed by the perfection of telescope technology.

In Figure 1 above you can see the Observatory’s 6 inch refracting Transit Telescope made by Troughton and Simms (1875-1877). Sometimes also called a transit ‘circle’ telescope, it was the workhorse of the Observatory up until the 1960s performing observations for timekeeping and meridian measures, and even serving as the early apparatus for the ‘Mapping the stars’ project. It is situated on a north-south axis that enables two precise measurements. The first is the position of a star in the sky.

Figure 2. Photographic glass plate negative, H. A. Lenehan at transit circle, photographer unknown, Sydney Observatory, Sydney, New South Wales, Australia, 1907-1908. Collection Museum of Applied Arts and Sciences.

The second measure is of time – which is possible to determine once a star’s position is known – is its split-second crossing or ‘transit’ from east to west. As seen in Figure 2, the observer reclined under the telescope, waiting for the rotation of the Earth to carry the star across the field of view of the across the fine spider web lines on the telescope’s eyepiece.

This precise moment of this crossing was used by astronomers to calibrate their ‘transit’ clocks. In the Transit Room is a postcard tacked on the wall, shown in my photograph below in Figure 3. Here we see the elaborate set-up that wired the telescope to the Observatory’s Hardy sidereal time regulator clock. Made by William Hardy (1795-1821), this clock was used for transit observations, up until the 1860 regulator clock by Charles Frodsham was installed, which was in use at the Observatory for over 100 years.

Figure 3. Lily Hibberd, Sydney Observatory Transit Room, photograph of a photograph taken in 2019 of the Transit Room from Henry Chamberlain Russell’s Astronomical results (1899-80-81), 25 x 19 cm, showing the Hardy regulator clock. Collection Museum of Applied Arts and Sciences.

Figure 4. Photograph, Frodsham longcase clock with electric switch clock, silver gelatin print, photographer unknown, used by Sydney Observatory, Sydney, New South Wales, Australia, 1979. Collection Museum of Applied Arts and Sciences.

A metre to the right, just next to the Transit Telescope is a little metal triangle. This is Sydney Trig. E (or Trigonometrical Station E), one of the markers I mentioned in yesterday’s Introduction, which was established based on a meridian survey of 1927 – and is notably at some distance from the Transit Telescope – which is already a curious sign of shifting ground. This reference was moreover used as the origin for the Trigonometrical Survey of NSW and the for the Triangulation of South Eastern Australia until 1966. 

Figure 5. Marker, trigonometrical station E, triangular, brass, JTC Richmond, Australia, 1927 2019. Collection Museum of Applied Arts & Sciences.

In the early 20th century, the Trig E (possibly a copy) was situated on top of the Observatory’s Time Ball Tower. This provided surveyors clambering up the Observatory tower stairs with a clear view to triangulate across Sydney city’s increasingly cluttered skyline, lugging their theodolites onto the roof until sometime in the 1980s. This marker was removed during renovation works at some point, but Astronomer Nick Lomb informs us that it was replaced as recently as 2012, to mark a new Department of Lands survey naming it Observatory E with its Longitude coordinates being 151° 12′ 4” E.

Now let’s get moving and head to Station 2!

Station 2

Sydney Observatory South Marker

June 9, 2020

On the front lawn of the Observatory today stands a funny white structure, in fact a thermometer shed – which forms part of yet another key historical role of the Observatory: meteorology. Under this shed is an obelisk-like pillar, which you too can see if you squint at the image below. This this is Station 2 –  the ‘south marker’ for the transit circle ‘s meridian.

Sydney Observatory’s original Meridian is supposed to emanate from the exact north-south axis of the 6 inch transit telescope and its extension is known as a ‘baseline’, which should in principle continue in a ‘great’ arc across the continent and around the world. If we wander out into the front yard Observatory it is possible to follow this line a few metres to the south marker.

Figure 1: Meridian South Marker: Google Earth.

The origins of the south marker are the subject of debate, as recorded in an Observatory blog post by Nick Lomb, dated February 8, 2012. The blog entry titled "The stone survey marker on the meridian line at Sydney Observatory has an unclear history", prompted a long dialogue between Nick Lomb, Andrew Jacob, and historian and astronomer Andrew James. According to James, Lomb’s doubts were founded since this marker was not in fact the first marker to be installed, but that ‘a new north-south’ had been determined after the transit circle instrument was installed at Sydney Observatory in February 1877, based on observations published by Chief Astronomer Henry Russell in 1881.

Figure 2: Photographic glass plate negative, front lawn of Sydney Observatory, photographer unknown, Sydney Observatory, Sydney, New South Wales, Australia, 1905-1915. Collection Museum of Applied Arts and Sciences.

The adjacent platform shown in Figure 2 (as it was with stairs, in the early 20th century) allowed the observer to align the marker with a collimation telescope just inside the Observatory and then to the Transit Telescope. Most curious is the question that James leaves hanging at the end of the blog, when James notes a small aperture visible on a brass fitting built into the left pivot of the transit telescope and asks: ‘Is this the basis of the meridian line of Sydney?’ In any case, James points out that these reference markers were often left in place because surveyors needed to recalibrate the baseline, which shifted due to continental drift.

I wonder about the impacts of the ever-changing conditions of the planet on such orthodox measures. Do they help us to grasp the paradox of time as we know it, which flows forward like an arrow and yet fluctuates according to rhythms and physical conditions? These are some of the questions to consider as we continue to pursue Sydney’s Meridian southward beyond the perimeter of the Observatory grounds.

Station 3

Sydney Observatory South Marker

June 9, 2020

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