Ten Tips for First-Time Telescope Buyers

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tfwthom

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From Sky & Telescope Skywatch ‘06<br /><br />Ten Tips for First-Time Telescope Buyers<br />By Alan Dyer<br /><br />1 Avoid any telescope advertised by how much it magnifies. Any claims of “powerful 600x model” are a sure sign of a poor telescope to be avoided, no matter how appealing the bargain price<br /><br />2 Don’t fuss over refractor versus reflector. One optical system is not better then the other, both can provide wonderful images. Make a choice based on aperture versus portability versus price.<br /><br />3 Avoid aperture fever. While more aperture provides sharper, brighter images, a bigger scope is also less portable. The best telescope is the one that you’ll use, and often. An expensive superscope that’s too heavy and complex to set up in a reasonable amount of time is no more value then a cheap miniscope if it always sits in the basement.<br /><br />4 Make portability a priority. In a first scope you’re best served by choosing one that can be carried outside in one or two pieces - for quick and convenient setup, for ease of moving around a backyard and for transport in a car. A big scope (more the 8 inches in aperture) might be practical only if ir can be left assembled, then uncovered or wheeled out in one piece.<br /><br />5 Consider your observing site. If you have ready access to dark skies, then a fast f/ratio, large-aperture reflector suitable for viewing faint deep-sky targets like nebulae and galaxies might be ideal. If you live under city lights, where the Moon and planets are likely to be the main targets, then a long-focal-length refractor or a Schmidt-Cassegrain scope might serve you better.<br /><br />6 Tailor the telescope to the owner. Select a scope with an eyepiece easily accessible to the prospective owner. The ideal scope for a short child won’t “fit” a strapping basketball player. Buyers with limited mobility or lifting ability might consider a lightweight 90-mm to 125-mm Maksutov or Schmidt-Cassegrain that can sit on a small table.<br /><br />7 <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>
 
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Saiph

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two things.<br /><br />#2 you say don't worry about reflector vs reflector....those are the same designs. So that's easy. You may wish to correct that <img src="/images/icons/smile.gif" />.<br /><br />Also, I'd go into #5 a bit (at least what you mean by an f/ratio, and long/slow vs short/fast) and why it helps.<br /><br />I would...but f/ratios are never something I really grasped well. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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tfwthom

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The focal ratio of an optical system is defined as the focal length divided by the aperture. So, a telescope with a focal length of 600mm and a 60mm aperture has an f-ratio or f-number, of f/10.<br /><br />Telescopes with smaller ("faster") f-ratios exhibit wider fields of view and lower magnifications for a given focal length of eyepiece. They're best suited for viewing extended deep-space objects, and require shorter exposures for astrophotography. F/6 or lower is considered "fast".<br /><br />Instruments with medium f-ratios of f/7 to f/10 excel for both low-and high-power applications, with the use of different eyepieces. High focal ratios of f/11 and up are ideal for planetary observations and splitting double stars, but yield lower image brightness for a given focal length of eyepiece and a narrower field. They also require lengthy exposure times for photography.<br /> <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>
 
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