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!


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.

| improve this answer | |
  • $\begingroup$ 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 '17 at 13:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.