Immediatlyyy 20 ! brainliest goes to the fastest and correct answer pl william herschel is known for: inventing the achromatic lens inventing the reflecting telescope building the largest refractor making a 48-inch precision reflector

I believe it's inventing the reflecting telescope. He built his own telescope with a magnifying power of 6,450. He also discovered Uranus and its two moons Titania and Oberon, named after the famous Shakespeare characters, but that wasn't one of the choices. 

It's cell theory. easy name i would think.