Telescopes for Beginning Astronomers
Although most people think of telescopes it may be best to consider binoculars first. They are portable, convenient and relatively inexpensive. Cheap binoculars are better than a cheap telescope. Consider something like 7 x 35 binoculars. The 7 is the magnification produced by the eyepiece, the other number is the aperture in millimeters. This size is light and easy to hold.
For those amateur astronomers, there are three types of telescopes available.
Refractors consist of lenses at both ends, and the most recognized type of telescope. They generally cost more per aperture inch than other telescopes, but their size makes them ideal beginner telescopes. It's best to avoid cheap department store models, as these quote large magnifications but have small, useless apertures. The job of a telescope is to collect an images light, not magnify it, so large magnifications actually make things worse and can alter data. Earthly telescopes usually have extra lenses to make an image appear right side up, but this extra lense can cut down the amount of light that reaches the eye. Therefore, the extra lense is left out of astronomical telescopes, which leaves images upside down. Since lenses can create false rainbow images around really bright objects, it's best to buy a filter to help correct the problem.
Next is the reflector telescope, and in this type, light travels down the tube and reflects off mirrors before leaving through an eyepiece. The reflector does not have chromatic abberation, and needs to be larger than a refractor in order to be as equally effective. Reflectors are the most comfortable telescope usually because of the eyepiece position, but the main mirror may need to be adjusted frequently. Luckily, there are kits to help with this problem. The most popular type of reflector is the Dobsonian, which has a mount close to the ground instead of a tripod, keeping you from kneeling and possessing an elastic neck to look upwards.
The third type of telescope is the Schmidt-Cassegrain. This uses lenses and mirrors to fold the light path back on itself within a compact tube. They are generally cheaper than refractors, but dearer than reflectors. They are more portable and easier to handle than the other two.
Telescope specifications may quote numbers.These have no affect on the image you see, but can affect the exposure needed if you get into astrophotography. It's best to avoid astrophotography to start with. Become familiar with the sky and your telescope first.
If you join a local astronomy club, you may be able to look into the different types of instruments, or you can just check your local library. Also, reputable astronomy magazines are available for reading reviews on quality telescopes, as well as manufacturers advertising.
Purchasing the largest aperture you can find is the best idea, but don't buy a telescope larger than you can lug around. Smaller telescopes are easier to set up and more convenient to use. You also don't want to waste your money on a large telescope if atmospheric pollution is high in your area, as this will prevent the telescope from giving you its best results.
It's best to spend most of your money on a buying a large aperture instead of telescope accessories. Doubling the aperture number will calculate the maximal practical magnification: i.e., a 70mm aperture will have a maximum magnification of 140x. Do not buy an eyepiece that is stated to stretch magnification past maximum aperture value. Start simple with eyepiece choices, such as a Kellner, which is a good all around eyepiece. If you place a Barlow lens between an eyepiece and focuser, magnification can be tripled.
In order to keep a moving object in view, a telescope may have to be moved repeatedly. To help with this, mounts and drives have been created. Electronic drives will help point the telescope, and it's important to have a sturdy mount.
It may be saddening to know that many textbook photos have false colors and are long exposures. The eye is not sensitive enough to see color in dim objects, and stars will always look like tiny light points.
So, let's talk about what you will see with a beginner telescope. With just a 75mm refractor or 150mm reflector, you can see nebulae, galaxies, moon craters, Saturn's rings, and even some of Jupiter's moons. All of these are amazing objects to view as you learn about the night sky.
Article Source: http://www.search-raven.com
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David Wildash posts information and resources on his website about Telescopes , and you can read more about buying a telescope
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by: DavidWildash
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