This equates to about 100x to 120x with the smallest telescopes, which is enough to see such wonders as the rings of Saturn and cloud bands on Jupiter. The maximum useful magnification for any telescope is about 50 times the aperture in inches, or two times the aperture in millimeters. As the magnification is pushed beyond that limit the image fails to reveal any additional detail and gradually breaks down into a dim, fuzzy blob. There is also an absolute limit, determined by the physical properties of light, to the resolution that is possible with any given aperture. As magnification is increased, and the image in the scope grows larger, the light gathered by the telescope is spread over a larger area, so the image is dimmed. The factor that limits the highest power that can be used effectively on a given scope is, you may have guessed, its aperture. Unfortunately, the first question most beginners ask is not "What is this telescope's aperture?" but "What is its magnifying power?" The truth is, any telescope can be made to provide almost any magnification, depending on what eyepiece is used. There are other criteria to be considered in selecting a telescope, but if you learn only one thing from this article, let it be this: the larger a telescope's aperture (i.e., the fatter it is), the more you will see. A telescope's aperture relates directly to the two vital aspects of the scope's performance: its light-gathering power (which determines how bright objects viewed in the scope will appear), and its maximum resolving power (how much fine detail it can reveal). This term refers to the diameter of the telescope's main optical element, be it a lens or a mirror. The single most important specification for any astronomical telescope is its aperture. Given the bewildering array of telescopes on the market, how does an enthusiastic but inexperienced consumer choose the right one? To answer this question we will explain the differences between specific telescope types, but for that discussion to be meaningful it is important first to understand some very basic points about astronomical telescopes in general.
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