Theoretically, with the right eyepiece even a small telescope can be set up to give 1000 or even 1,000,000 power. Imagine that you want to buy a telescope for multiple purposes, not just astronomy viewing.
Astronomical telescopes display things upside down, unlike the typical sporting telescopes.
Tycho Brahe's detailed observations of the heavens, from which Kepler derived his laws of planetary motion, were made without any telescope at all. How could such important work have been done with the telescope. According to Louis Bell in his definitive work, The Telescope , at the time spectacles were invented, the dominant eye problem they could be used to correct was presbyopia , the farsightedness that often accompanies aging. The weak convex lenses used to treat this condition did not produce a telescopic effect. This was not until perhaps the late 1500's, and only then was the combination of concave and convex lenses that formed the first telescope even possible.