A good general rule of thumb is that any magnification above 50 per Wrong! A lot of telescope manufactures would like you to believe this, but it is farįrom the truth. The higher the magnification the better, right? Length of 5 millimeters will yield a magnification of 140X.Ħ. The same telescope with an eyepiece that has a focal Length of 700 millimeters, using an eyepiece, which has a focal length of 18 millimeters, The eyepiece, which is the focal length of the eyepiece. Once you know your focal length, all you have to do is divide it by the number on 48 inches is the equivalent of 1200 millimeters. For example, a six-inch telescope withĪ focal ratio of 8 (or f number 8) would have a focal length of 6 inch X 8, or 48 In these cases you need to multiply the focal ratioīy the aperture and convert to millimeters. Some telescopes won't tell you the focal length,īut will tell you the focal ratio. It might read something like ``fl=700mm''. The easy way is to look on the telescope, or in the instructionīook. Tocalculate your magnification you first need to know your focal length. One should yield a low magnification, one a high magnification, and You should have at least three eyepieces, though The light collect by the primary lens or mirror. Those little lenses are called eyepieces and they act like magnifying glasses to magnify What about all those little lenses, what are they for? Hundred dollars to three thousand dollars.ĥ. These telescopes, well equipped, range in price from about five Refractor, a six to eight inch reflector, or an eight inch Schmidt-Cassegrain areĪll excellent choices, and are probably the most commonly used telescopes by seriousĪmateur astronomers. Large, poor quality telescopes without any of the accessories. Larger is better, but a smaller, high quality, telescope is to be preferred over a In price from a low of about one hundred dollars to a high of about one thousand dollars. Although thereĪre exceptions, these are minimum aperture worth considering. Mirror at the bottom of the tube, and should measure about four inches. Like reflectors, the aperture is a measurement of the diameter of the light collecting For reflectors the minimum should be about 4 inches. Reflectors the measurement is the diameter of the mirror at the bottom tube, whichĬollects the light. A refractor should measure at least 2.4 inch, or 60 millimeters across. Measures the diameter of the lens at the top of tube. The most significant way to measure a telescope is its aperture. Picking a telescope is a series of trade-offs. Is no telescope on the market that is the best choice for every type of observing. That some telescopes are better suited for certain types of objects than others. Then a long focal length refractor, or Schmidt-Cassegrain might be your best bet.Īny telescope will work reasonably well on any type of object. Nebulae then a reflector might be your best choice. If you are interested in faint diffuse objects like galaxies and Live in a bright urban area) then a small refractor or a Schmidt-Cassegrain has a If portability is an important factor for you, (and it should be if you It all depends on your interestsĪnd needs. Of the three there is no single ``best choice''. Refractors, reflectors, and Schmidt-Cassegrains ( here is a nice description of the difference between a refractor and a reflector). There are three main types of telescopes commonly available to amateur astronomers: Research, and ask yourself what you want to do with the telescope. Investing hundreds or thousands of dollars in a telescope is to do some reading and The most important thing you can do before The important thing to consider is not how much you spend, but how Depending on your needsĪnd interests you can spend as little as a hundred dollars, and as much as ten thousandĭollars, or more. How much to spend on a telescope is a very difficult question. One of the best ways to accomplish these is to spend as much timeĪs you can exploring the nighttime sky with a good pair of binoculars. Before buying a telescope you should be familiar with most of the major constellations,īe proficient in the use of star charts, and have a fundamental understanding of someīasic astronomy.
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