I found a table of historically largest telescopes here, so I'm guessing it's the Hale Telescope of the Palomar Observatory on Mount Wilson. However, that Wikipedia article warns that size is not everything when it comes to light-gathering-power.
So I want to know: In the 1960's, what was the best optical telescope on Earth, in terms of apparent magnitude or light-gathering-power? And what is the faintest apparent magnitude it could see? I'm hoping it will be able to observe things down to an apparent magnitude of at least 15.