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I'm looking at Saturn through a modest telescope at 50x. What point in space, expressed as the distance from Saturn, let's say it's 750 million miles from Earth, would I need to view Saturn with the naked eye and see it at the same apparent size as viewed from Earth at 50x. How do I estimate this in general for other objects as well. Thanks!

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Just divide the actual distance by the magnification. In your example that would give 750 million /50, which is 15 million miles. (Actually saturn is currently over 800 million miles from earth).

The reason this works is that a magnification of M means the object is M times its apparent linear size, which requires being M times closer. This is a slight approximation, but is fine for distant objects.

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  • $\begingroup$ Hi. Thanks Dr. Chuck. I'm glad it's a simple matter. So I would need to be 15 million miles from Saturn or 745 or 785 million miles from Earth. Amazing bit of distance jumping through a simple telescope! Thanks again $\endgroup$
    – Kevin
    Aug 4, 2017 at 13:44

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