ASTRONOMY
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How important is magnification
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What is the best telescope for a beginner? Small telescopes are awkward to manage, and to give a telescope to a small child as a present often courts ruining their expectations. Be prepared to get involved with setting the instrument up and learning how to use it yourself in conjunction with your child.
Telescopes come in two distinct sorts – static and driven. Ideally you should get a drive motor to move the telescope across the sky to compensate for the rotation of the Earth. In order for this to happen, the telescope must be set up correctly, and this will be set out in the instruction books that come with your telescope. A telescope without a drive will keep pointing at the same spot, and any object set in the field of view will move out quite quickly as the Earth moves.
In my opinion it is not worth getting a small telescope with an aperture of anything less than 100mm ( 4 inches). This will usually be a Newtonian reflector, on a tripod, with a variety of eyepieces. Those not driven will have two flexible handles to move the telescope through the sky. It should also have a small finder telescope to use for setting up – a small refractor only 20mm in diameter. Two basic accessories are needed in conjunction with a first time telescope user. These are an annual handbook, and a small planisphere. These will tell you what is available and where to look for objects.
Often, the use of a pair of binoculars with a planisphere is a good introduction to the sky, and a whole lot cheaper.
How important is
magnification:
While it is important, magnification is highly over rated. The actual magnification comes from a formula, where one divides the focal length of the telescope by the focal length of the eyepiece. Thus a telescope of 1000mm focal length, using an eyepiece of 20mm aperture will have a magnification of 50x. This is ample for a small telescope. Advertising on the carton may well claim 500x magnification ( if we use a 2mm eyepiece on a 1000mm telescope) but note you only have a tiny eyepiece, and the amount of light getting through there is very small – to the extent that it is impossible to use. Beware of claims of high magnification – instead get a telescope with at least 100mm aperture.
In all my time as an astronomer I have never seen anything that I could not explain. 95% of all UFO calls are caused by the bright planet Venus, which gets very bright at some parts of its orbit. Satellites move in a direct path across the sky – they’re in orbit around the Earth. Any object moving around in various directions has to be man made – beware of the hoaxers in our community. Following a series of calls in the early 1990s I was able to track the origin of a week long hoax UFO campaign – and found it was high school students sending up hot air balloons suspending a light source. Strange sights often occur in our skies – astronomers just need enough information to work out what they are caused by.
Venus is generally called Earth’s sister planet, as it is of similar size, and frequents the same area of the solar system. At times when Venus is well East of the Sun, it appears as a bright object to the West as dusk is falling. It is the first object that folk notice, and so is called the evening star. It’s not a star, but shines in the same way.
Conversely, when Venus is well West of the Sun, rising3 hours before sunrise, it is very bright in the mornings, and is called the morning star.
These are terms used to describe the same object – a piece of rock has been drifting thought Space, and has been dragged into the Earth’s atmosphere by gravity. As it get ever faster in its motion, the rocky or metallic surface heats to glowing just by friction with molecules of air, and we see it as a light moving quickly across the sky. Sometimes it is possible to see these in the daytime. Every now and again they break the sound barrier and cause a sonic boom, as happened in Perth on May 1 1995
An object moving through the atmosphere is called a meteor. When it reaches the Earth it is called a meteorite, to indicate it has landed.
From Space, the light from the stars is dead steady. However, as light passes through our atmosphere, different density layers of air bend the rays of light in unpredictable ways. This means that we see different parts of the spectrum, and starlight may flash all colours of the rainbow. It’s called scintillation. The use of Space telescopes is one of the best ways of getting around this problem for astronomers. Another way to lessen scintillation is to put telescopes on high mountain peaks – the prime Earth based Observatories are at 5000 altitude on Hawaii and in the Andes in South America.