Saturday, 1 January 2011

Skywatch - Introduction

Since you monkeys could walk upright you have looked to the stars with wonder. As our genes gradually replaced those of the Neanderthals, your natural instinct was to look skywards but rarely did you fully understand why. It was, on occasion, critically important to life on Earth. It will be again!

So with that in mind I will give you all a tutorial in how to look, what to look with, what to look at, and ultimately what to look for. So pay attention and don't fidget!

Star Chart

In time it will benefit you to have a book of these. In time a trip to a planetarium would be beneficial. For now here's how to get started. Assuming you have nothing but the naked eye to begin with. For tens of thousands of year you had nothing but the naked eye yet you still managed.

The oldest star chart known may be a carved ivory Mammoth tusk that was discovered in Germany in 1979. This artifact is 32,500 years old and has a carving that resembles the constellation Orion.

A drawing on the wall of the Lascaux caves in France has a graphical representation of the Pleiades open cluster of stars. This is dated to 33,000 to 10,000 years ago. Researcher Michael A. Rappenglueck has suggested that a panel in the same caves depicting a charging bison, a man with a bird's head and the head of a bird on top of a piece of wood, together may depict the summer triangle, which at the time was a circumpolar formation. Another star chart panel, created more than 21,000 years ago, was found in the La TĂȘte du Lion grotto. The bovine in this panel may represent the constellation Taurus, with a pattern representing the Pleiades located just above it.

The Farnese Atlas is a Roman statue depicting the Titan Atlas holding the celestial sphere on his shoulder. It is the oldest surviving depiction of the ancient Greek constellations, and includes grid circles that provide coordinate positions. Because of precession, the positions of the constellations slowly change over time. By comparing the positions of the 41 constellations against the grid circles, an accurate determination can be made of the epoch when the original observations were performed. Based upon this information, the constellations were catalogued at 125 ± 55 BC. This evidence indicates that the star catalogue of the Greek astronomer Hipparchus was used.

Odd these all occurred just after the Neanderthal genes all but died out and when God went into phase two of her 'evolutionary boost' project.

There are endless things to be seen with the naked eye. Obviously there is the Moon, with clearly visible craters and an occasional lunar eclipse where it passes through the Earth's shadow. The five nearest planets are visible to the naked eye. Then there are the meteor showers, man made satellites and of course you can familiarise yourself with the various constellations.

First you need to let your eyes adapt. This can take 15-20 minutes and avoid looking at lights. Wear warm clothing and cover your head in winter (beware of insects and bugs in summer). A flask of tea or coffee and some dried fruit or nuts are also welcome as is an adjustable reclining garden chair.

For those of you with binoculars other possibilities arise. Binoculars are, in certain aspects of sky watching, the best instrument of all to use. For less money than you would pay for a poor quality small telescope, you can buy a well made pair of binoculars with quality optics that will last a life time. Through binoculars you will be able to see the craters on the Moon, the moons of Jupiter, and 5-10 times the amount of stars you can see with the naked eye. If you consider purchasing binoculars in the future here's what to look out for.

Prisms are used in binoculars so what you see is the right way round otherwise things would appear upside down and switched left to right. There are two main variations of prisms.

The porro prism is the simplest and most commonly used. The roof prism is significantly lighter, more compact and more expensive. The performance of the binoculars depends on the size of the lenses at the front of the binoculars. Combination of eye pieces and lens have a wide range of possibilities.

A pair 7 x 50 which always uses the porro prism design is recommended. The 7 refers to the magnification and the 50 to the diameter of the lens. While 10 x 50 and 8 x 40 are also okay for use they don't match the light available so well. Binoculars with 80mm lenses are available but they are heavy and you would need a tripod.

A lot of the cheaper binoculars are useless. Unless the two optical paths are exactly alined you will see slightly different images with each eye. To test the alignment get a friend to cover one lens with a book as you look at a distant object. Keep both eyes open then get them to take the book away quickly. If you see two images just before your brain merges them into one the binoculars are out of alignment.

Now you're ready!

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