14Apr2018

Night Sky Lesson For Beginners

Ever wondered how many stars were in the night sky?

“Twinkle, twinkle little star – how I wonder what you are.” The words to that popular tune were written by Jane Taylor in 1806 and I bet there isn’t a person alive who hasn’t gazed up at the stars and sung that to themselves.

Well we do know what stars are and a whole lot more. But stars don’t really twinkle! It’s an optical illusion. If you were in space stars would be just bright, unblinking points of light. It’s our atmosphere which scatters the starlight before it reaches your eye, causing that ‘twinkling’ effect. Astronomers use this twinkling effect to calculate what the seeing is going to be like from one night to the next.

When you see a star low down on the horizon twinkling like crazy you can bet it’s not going to be a good night for the telescope. The atmosphere is too unsteady. If a star halfway up the sky also twinkles a lot it’s time to watch that video you’ve been putting off!

If you’re just getting started in astronomy, the best thing to do is to first spend some time under the stars with just your eyes and get acquainted with the brighter stars and constellations. Purchase a good sky guide and star chart. They’ll go a long way to help you familiarize yourself with the night sky.

When using a sky chart or telescope at night be sure to use a dim red light or a red-filtered torch. That way your eyes stay dark-adapted because white light will shrink the pupils of your eyes. Use red cellophane or red plastic across the front of the torch lens, you’ll retain your night vision and you’ll see much dimmer objects.

I’ll bet you didn’t’ know, the colour you see in books or on posters is not what you’ll see in your telescope. These colours only show up on time exposure photographs because cameras can gather much more light than the human eye. Don’t feel disappointed, it’s just one of the vagaries of being a human being.

By the way, did you know that all photographs sent back to Earth by the Hubble telescope are in black and white? True! The colour is added in the lab but not to trick you. Astronomers do that to bring out the detail.

Scanning Southern Skies

When you look into the sky on a clear night another world appears. Stars twinkle, planets glow, meteors shoot across the sky, and your imagination expands

Have you noticed, the nights are getting longer, and colder! People are dusting off their supporters garments and getting outside to barrack for their preferred football code. Anyone at night time practice can take some time off to stare up at the winter skies, see the Milky Way and a couple of million stars. You might even see one zip by?

No wait, stars don‘t do that do they? They’re called ‘shooting stars’ but that’s incorrect, stars don’t fall out of the sky. Shooting stars and falling stars are both names that people have used for many hundreds of years for what we now call meteors.

OK, let’s get out there and spend some time under the stars and try to spot some. For June, shortly after sunset and looking to the west, you’ll be able to see the brightest star in the night sky. This is, of course, Sirius, the Dog Star. A star that shares its name with a ship of the First Fleet, HMS Sirius, and of course, the character from one of the Harry Potter novels, Sirius Black.

There are about 2,000 to 3,000 stars that you can see from a fairly dark location, if you’ve got good eyesight and you haven’t been smoking a cigarette, of course, because that affects your night vision. Hey, time to check out some constellations and signs of the zodiac.

By the way, zodiac simply means ‘Path of the animals’. So, all of the zodiacs are indeed animals bar one. I’ll leave you to think about that. There are 12 traditional signs although astronomers now recognize 13, with Ophiuchus being the 13th.

What’s That familiar Shape?

Rising in the east is the only zodiac constellation that really looks like its namesake, the giant constellation Scorpius, or ‘Scorpion.’ You should be able to see its distinctive curly scorpion shape and its glowing heart, the red star Antares, which comes from its ancient name ‘Rival to Mars’.

Lying near the centre of the beautiful Milky Way Galaxy, Scorpius is a fabulous part of the sky to scan with binoculars. Many people think you need really powerful ones but the humble 7×50 home binoculars will work perfectly well here.  Scan the heart of the Milky Way, around the tail of Scorpius and near the constellation of Sagittarius below it. It really is quite a beautiful area of the night sky.

Scan along Scorpius and you’ll be able to see a couple of rather spectacular objects. There is a globular cluster of stars there called M4. Yes, not a terribly imaginative name, but M4 is nice in a telescope. You’ll also be able to see M6, and M7, which are young clusters of stars, intriguingly famous in some indigenous mythology from central Australia.

No, it Isn’t Climate Change

Watch for the seasonal changeover coming up. This month we’re heading for the June solstice. The North Pole of the earth will be tilted toward the Sun. This is the first day of summer (summer solstice) in the northern hemisphere and the first day of winter (winter solstice) in the southern hemisphere.

You know, temperatures on our planet are not determined by the distance of the Earth from the Sun. Rather it is the angle of the Sun’s rays striking the Earth.

The seasons are governed by the tilt of the Earth’s axis in space as it journeys around the Sun in a year. When the South Pole of the Earth is tilted towards the Sun, this is our Summer. Six months later, when the South Pole is tilted away from the Sun, it’s our Winter. In between these we have Autumn and Spring. Simple huh?  Source: Dave Reneke

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