By
Eugene O'Connor
Starting in this edition , Shoalhaven Astronomers present a regular column on what can be seen in the night sky over the coming weeks. First a word about Shoalhaven Astronomers.
We are a group of amateurs who meet on the third Friday of each month at 7.30 p.m. at Falls Creek Public School. We have about twenty five members of both sexes - but mainly men, and our common interest is studying the night sky and sharing our interest with schools and community groups who often call for help in a demonstration of the wonders of the stars, planets, comets and deep sky objects. We have an annual Public Viewing Night in the Harry Sawkins Park. We often travel to well known Australian astronomy institutions and attend professional lectures in the major cities. This year we entered a float in the Shoalhaven Spring Festival for the first time and were absolutely overjoyed to win third prize. Further details about membership or matters astronomical can be had by phoning Jack our President on 232255
Viewing the Night Sky
In a future article more detail will be given on telescopes suitable for viewing objects in the sky. For the moment, all of the objects mentioned can be viewed with the unaided eye or through a good pair of binoculars. The best choice for viewing the night sky is binoculars with a power of 7X50. The ë7' refers to magnification and the ë50' refers to the diameter of the main lenses in millimetres. In astronomy , light-gathering is far more important than magnification since we are studying dim objects for the most part.
How do I find my way about?
This is the first question asked about astronomy. Rightly so. You go outside and if it is a clear dark night with no Moon you see what seems many thousands of stars, looking more or less the same. Wrong. Let me dispel this myth straight away. The most stars we can see with the human eye on any given night is about 2,500 and the stars look the same for the very reason that streets in a new city look the same. We are just confused at first. After a little bit of familiarity and a good street map - or star map- we can become as familiar with the night sky as a good cabby becomes familiar with the city streets he plies each day.
Our clever ancestors started to notice - with a great deal of imagination- that the stars formed patterns in the sky, as a child sees shapes in the clouds, and they named these patterns after birds or animals or mythological creatures. Of course not all the star groups, or constellations, resemble what they are called after, but don't be put off by this. Some do. Lucky for us the Southern Cross does resemble a cross and we have a flag that reminds us of this pattern of stars regularly. Others that fit this category are Grus, the Crane, Leo the Lion and Canis Major the Greater Dog, though this last may take a longer look to recognise.
In these articles I will presume that skywatchers know just one or two Constellations, such as the Southern Cross and maybe Orion, the Hunter, which contains the sauce-pan. Should you seriously want to learn more, find a small atlas of the skies or better still a star-wheel or Planisphere, and do what every keen tourist does with a good street map in a new city. Start from a place you recognise and work outwards from there. You will soon be the taxi-driver who knows all the streets in the night sky!
So what's up there now?
I have good news for you. You are starting out on this sky tour at the very best time. Our brightest planet, Venus is high in the Western sky on dark and it remain in the Western sky until ten p.m. If you have good binoculars and a steady hand you will notice that this star-like object has, in fact, the shape of a crescent Moon at the moment and if you occasionally watch it between now and Christmas you will notice two things. 1) As time goes on it seems to get larger and crescent grows thinner. 2) It starts to head lower and lower towards the horizon and sets by 8.30 by the end of the year. More on this next time. Another bright star-like object and far higher in the Western sky than Venus is our largest planet, Jupiter. Again, good binoculars reveal the disc of this planet and you may even spot it four biggest moons, first seen by Galileo in a recently invented telescope in 1610. These satellites change their positions from night to night. If you are not sure which bright ëstar' is Jupiter, the young Moon on the evening of December 5th lies alongside it. Until next time, good viewing.