04-10-2008 October night sky (Article 157)

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Simon Kenny
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Location: Shannon, Co. Clare, Ireland

04-10-2008 October night sky (Article 157)

Post by Simon Kenny » Tue Dec 30, 2008 8:47 pm

October night sky (Article 157)

The long nights are on the way in, it’s starting to get dark at 7pm these days. Jupiter is drifting into the evening twilight; it is visible as a very bright star in the southwestern sky in the hours after sunset. Venus is visible throughout the month as a bright star right on the horizon just after sunset, you need a perfectly flat horizon to have any hope of seeing it. Never look at the Sun with a telescope or any optical aid, instant blindness will result. Saturn is visible on the eastern horizon before sunset from 5.30am onwards in the constellation Leo. If you have seen Saturn through a telescope in the recent past, you might notice that the current view of it shows the rings are closing, by the end of the year they will be almost edge on so making them almost impossible to see. They are about 1 mile in thickness yet are over 250000 miles wide, that’s about as far as from here to the Moon (approx).
The sky is also making the transition from the summer constellations to the winter variety. Constellations such a Cygnus, Lyra, and Hercules are on the way out while others such as Pegasus, Pisces, Andromeda, Orion, and Taurus are on the rise. This happens because of the Earth orbiting the Sun over the year.
The plough is seen just above the northern horizon. It is actually part of another constellation called Ursa Major, namely “the great bear”. When looking at the plough it presens you with an easy way of finding the North Star. The 2 right most stars act as a pointer to the pole star (Polaris). If you draw an imaginary line joining these two stars that is about 5 times the distance between them you will find Polaris (see diagram). One common misconception by many people new to astronomy is the belief that Polaris is the brightest start in the sky, far from it! It is infact number 49 in the brightest stars list. The plough also presents you with an eye test that was used in ancient china and medieval times. If you look at the second star in from the left (Mizar), you might find that a fainter star lies in the 10 o’clock position right next to it (Alcor), if you can see this then you have good eyesight, if not then you need glasses.
Halloween is on the 30th of this month and it is interesting to note that the festival has some astronomical links. It is placed midway between the Autumnal Equinox and the Winter Solstice, making it an important mid season event for the ancient Celts. They chose cross-quarter dates as a time to ring in the beginning of each season so they called the day Samhain, or "summer's end"; the day was also their New Year's Eve. So make sure you wish all those trick or treaters a happy new year!

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