The Night Sky

Talk at the DRB Nats, July 2019

Starting with Sputnik and ending with Santa, we took a walk through the southern night sky.

Our guide was Arthur Harvey, a volunteer at the Perth Observatory in Bickley*. Arthur’s interest in observing the night sky started with Sputnik in 1957 and so, having had his eye on the sky since the start of the satellite era, he was a wealth of information on how, where and what to look for.

To ensure we’d start at the start, Arthur provided us with the map to read the sky. The ‘right ascension’ and the ‘declination’ coordinates – similar to latitude and longitude on land and sea – allow us to agree on the location of the 88 modern constellations (and billions of other objects). Conveniently, we’d had an earlier 5-minute presentation by Bill Tomlinson on how to use a sextant and chronometer. As well as the coordinates, we also need to know the ‘epoch’ in which the coordinates were recorded. Arthur showed us why, as given a long enough time frame the stars move relative to one another.

Before we reached the constellations, Arthur lifted our eyes to the world of meteorite observation. While these objects are tracked on their paths across WA using a sophisticated set of cameras, the Observatory is interested to hear from amateurs on where meteorites are seen, the time, and direction they are travelling. For the man-made objects moving across the sky (ISS, Hubble) he recommended Heavens Above website .

One of the tips for tracking the movement and location of meteorites, was to use our hands to measure the angle from the horizon. One finger width at arm’s length is equivalent to approximately one degree, a fist held to the sky is 10 degrees, and a fist with the little finger and thumb held out is roughly 25 degrees.

Finally, the constellations, where Arthur unleashed a deck of slides and animations showing in magnificent detail the upside-down constellations we see in our southern sky, from the familiar signs of the zodiac to the sky-spanning Argo Navis, the ship of the Argonauts. This constellation is now divided into three smaller ones; Vela [sail], Carina [hull] and Puppis [deck]. The Crux of the talk was how to use it to find south, and as a bonus, how to find south using the Magellanic clouds.

Then into the future, to contemplate the collision of the Milky Way’s 300 billion stars with the even larger Andromeda galaxy, and how our favourite Orion changes shape over a million years.

In winding down the talk and picking out his personal favourite constellation, Auriga the charioteer, Arthur finished with one last word of wisdom, being where to look on a clear Christmas (in July?) night!

It was a great presentation, stretching many stargazers, and surely tempting a few more of us take our binoculars outside at night. Thank you Arthur!

Chris Carter

* In the 70’s, it assisted in verifying the rings around Uranus