![]() ![]() This is the final element of a telescope that you should be aware of. ![]() This in turn means that a larger focal ration will provide a narrower field of view whilst a lower focal ratio is the opposite. The basic premise of the focal ratio is that the larger the number the higher the magnification. For example the focal ratio of a telescope with a 70mm telescope with a 800mm focal length will equal f/11.42. In order to get this number you have to divide the focal length by the apeteure. The focal ratio describes the ratio between the aperture and focal length. If the focal length is shorter, you’ll get a wider field of view meaning you’ll be able to see more celestial objects whilst looking into the lens whilst a longer focal length means you get a narrower field of view so, it’s better on closeups of planets. The length between the focal point and your eyes determine your field of view. The focal length is also measured in millimetres. The distance between the focal point and where the light reaches your eye is the focal length. In order to actually see out into space, the light rays must first converge into a single point, other wise know as the focal point. There is a massive difference between smaller and larger aperture scopes, for example the difference between a 80mm lens and a 160mm lens, the amount of light captured within 160mm will be 4 times that of the former meaning you’ll get 4 times the detail and contrast (roughly speaking). What this means is that the larger the lens the more detail the telescope will be able to capture in terms of the contrast and detail of celestial objects within outer space. In terms of the number, the mirror lens, otherwise know as the aperture, will determine how much light the telescope is able to capture. So in order to get the best experience, you’ve got to decide how large you want the aperture of the lens to be or compromise power portability if that’s what you’re after.
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