Quote:
Originally Posted by andrew2008
have heard people say this before. why does the focal length affect which EP's are compatible??
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As you know, focal length determines magnification, so the shorter the FL of the EP, the less mag you get..but it's the focal ratio of the scope that may determine the usability of the EP. The lower the focal ratio, the more difficult to correct for aberrations (eg coma). That's why high-end wide FOV EP's are expensive, and why you need to consider the FOV of the EP. A wider FOV EP in an f/5 scope may deliver more stars, but also more stars with noticeable coma. A high-end EP may deliver the same FOV but with fewer aberrations.
Mark