The short-focus telescope invented by M. Leon Jobert, director of the Popular Observatory in Paris. The shorter a scope's focal length, the wider its field of view. For many of the deep-sky treasures (diffuse nebulas, open clusters, and big galaxies) a wide field is desirable to frame the whole object in surrounding starfield. Long focal lengths show a narrower patch of sky, which is ideal for viewing small objects like planets and lunar surface details. Short-focal-length optics introduce certain optical aberrations. Short refractors have more visible chromatic aberration than long refractors. | |
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Credit: | Science Photo Library / Science Source |
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