Reflecting telescope pros and cons8/8/2023 ![]() I’ll touch upon how these problems have been addressed in the various designs available. Field curvature is also a common issue where the best focus lies on a curved plane resulting in the stars at the edge being blurred, field flattening lenses are employed to correct this issue. At the centre of the field your stars may be sharp points but at the edge they may appear distorted and comet like (hence the name). In the section on refractors you may recall I mentioned field flattening, this corrects yet another aberration called off-axis aberration where objects at the edge of the field of view suffer from various types of distortion, coma being the one that causes the most angst. ![]() Spherical aberration is eliminated by using a parabolic mirror where the reflected light achieves focus at the same point. You may have heard that term before as this is what plagued the Hubble Space Telescope before the shuttle mission to repair it. This causes blurring known as spherical aberration. This doesn’t mean that reflectors are problem free, with a spherical mirror (the mirror being a section of a sphere) light rays from the edge of the mirror achieve focus nearer the mirror than those from the centre. Reflecting telescopes, as the name suggests, use mirrors to collect and focus light and so are free from chromatic aberration.
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