The Night Sky in December.
A Telescope for Christmas?
When I was a young boy, my father bought me a telescope that he had seen advertised in a national newspaper. It was described as having a magnification of hundreds and a cardboard tube nearly 2 metres long. He had no idea what he was buying but wanted to buy me a present that would encourage my interests.
It was an amazing present! I spent many dark nights trying to hold it steady and pick out details of the moon. I was hooked! What eventually dawned on me and has been confirmed by years of observing is be careful what you buy! Some advertised telescope magnifications can often result in a very large blurry image. Additionally, a telescope needs to be held very steady to be of any use and a tripod or mount needs to be added to the equation. In fact, you will get just as much pleasure and enjoyment out of a decent pair of 10x50 binoculars as a poor quality telescope. The first number (10) is by how much they will magnify an image eg. x10. The second number (50) is the size of lens that collects the light; the bigger the better, but too big and they will be too heavy! This specification means they are easy to get out and observe during a break in the clouds and you often have a wider field of view. All that being said, a good quality telescope is hard to beat and that first one, regardless of quality, captured my imagination and set me on the path of a long lasting love of astronomy. There are two main types, refractors (which use lenses) and reflectors (use a lens and curved mirror). Some can even locate amazing objects in the night sky automatically. The development of telescopes in recent years for home use has been remarkable. But please remember whatever you buy, when using it, don’t point it at the sun!
The Twins.
During this month looking east late evening you will spot the twins or Gemini. Looking at my diagram you will see two ‘matchstick’ people holding hands. Their heads are made from two bright stars, Castor and Pollux. The Greeks told a tale of two half-brothers searching for the Golden Fleece with Jason - Castor, the son of a king and Pollux, the son of Zeus. The search was made into a film which is often shown over Christmas. Watch out for it! Nearby is M35, a cluster of stars visible to the naked eye. Binoculars or a telescope will reveal even more stars. The cluster covers an area the size of a full moon so it should be easy to spot.
Comet Wirtanen – Best Comet Viewing of 2018!
Every five years or so we have a visitor who comes quite close to Earth, circling our sun in a large elongated orbit. Comet Wirtanen will visit us again this month and will be the closest and brightest it will be for twenty years. It promises to be the best comet viewing of the year. On any clear night this month you will be able to spot this comet. Look out for it around the 7th when we have a New Moon when it should be easy to spot (close to the Pleiades). This icy lump of debris is just over 1km across. As these huge ‘dirty snowballs’ orbit the sun they start to melt, releasing gas, dust and particles which often give them their characteristic tail. The tail always points away from the sun and appears odd when moving away from the sun with its tail ahead of its movement. Of course over the next few years the Earth will pass through the debris that it has left and hopefully give us a meteor shower to remind us of its visit until the next time.
As the dark nights draw in, I hope we can all appreciate the privilege of living in a village which boasts a rich, dark sky at a time when more and more people are denied this fundamental right.
I haven't seen the comet in person yet but images on line show a nice tail developing!