The Keck telescope on Mauna Kea has an angular resolution on Earth of half an arcsecond.

Question

How far away (in meters) could you read ("resolve the letters of") a book with 3 mm square type, using the Keck telescope on Earth?

Answer 1

1/2 " = 2.424*10^-6 radians

So, find r using

s = rθ

Answer 2

Thanks a lot for your Help Steve