![]() Most refractor telescopes suffer from a defect called chromatic aberration. This is necessary to get decent images within a reasonable budget. Its focal length is about 10 to 13x its diameter (for example, a diameter of 60mm will have a focal length of about 700mm). The longer the focal length, the greater the magnification (but watch out! As you’ll see later, high magnification is not always the best).Ī standard refractor telescope is always pretty long. ![]() ![]() Feel free to use it to determine what you’d be able to see in a telescope according to its aperture! ![]() This simulation has been made with the Stelvision simulator. A telescope’s aperture influences both the brightness and the amount of detail. Simulation of an observation of the Moon with two scopes of very different diameters (60mm and 300mm). After a few years of stargazing, deep-sky enthusiasts may start thinking of getting larger scopes (of 250mm up to 400mm) in order to explore even more distant galaxies or faint nebulae in the sky. Under ideal conditions (flawless telescope, stable atmosphere), a diameter doubled in size will reveal twice as much detail.īasic telescopes for beginners usually have an aperture between 60 and 150mm (60-80mm for a refractor telescope, 100-150mm for a reflector telescope). the diameter also determines the images’ amount of detail.The bigger the scope, the more light it gathers the diameter of the aperture determines the images’ brightness.If budget isn’t an issue, it is best to go for an aperture that is as big as possible since: The aperture is the most important thing to consider when evaluating the power of a telescope. For example, a telescope with an aperture (or diameter) of 70mm and a focal length of 900mm will be presented as “70/900 telescope”. The first is the aperture, or the diameter of the lens or mirror (D), generally expressed in millimeters.Ī telescope is often described with reference to its aperture and focal length.The Most Important Factors of Your Telescope: Aperture and Focal Lengthīoth refractor and reflector telescopes depend on two main optical parameters to portray their power. This is because a mirror is easier to make than a good refractor objective. While it is not difficult to adjust the reflector mirrors, it can admittedly be confusing for beginners.īut when telescopes get to be a certain size, reflectors come out on top for their cost. A reflector telescope will actually need to be aligned from time to time to get the best image. Is one telescope better than another?īeginners usually opt for refractor telescopes, which are slightly easier to use than reflector telescopes. Illustration: Valentine Dubois – Stelvision. A reflector telescope uses mirrors, which is placed at the back of the optical tube.ĭiagram of how a Schmidt-Cassegrain or Maksutov-Cassegrain telescope works.A refractor telescope uses an optical lens, which is placed at the front of the optical tube.Reflector and refractor telescopes work similarly, though their designs are quite different. It also magnifies the objects observed to reveal details that are invisible to the naked eye (such as the Moon’s craters, Saturn’s rings, etc.).First off, it amplifies the light coming off from the stars and reveals what the naked eye cannot see (for example, a distant galaxy).The optical part of telescope has two roles. These can come with your instrument or be purchased separately. Make sure you carefully consider these different parts before you make your choice, since a good optical tube won’t do much good if the mount is unstable or not very accurate. Your telescope should also be equipped with quality accessories. ![]()
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