What is a telescope? How good are modern telescopes? | Explained

The modern telescope is a window into the universe, a sophisticated paintbrush in the hands of skilled astronomers that brings the fantastical wonders of the cosmos into view. The maximum practicable lens size in a refracting telescope is around 1 m. The world’s largest refracting telescope is at Yerkes Observatory in the U.S., with a 1.02-m lens. The human eye’s limiting magnitude in ideal conditions is +6.5 while that of the toy telescope is +11.2. Limits to telescopes A telescope with a higher limiting magnitude is required to look deep into the universe, which demands a larger primary mirror. Advanced telescopes around the world The largest telescope to date is the Large Binocular Telescope, which has two 8.4-m-wide mirrors and an effective combined aperture of 11.9 m. It is located at the Mount Graham International Observatory in Arizona, USA.