system
Given the following post, respond as if you're commenting on Reddit:
human
Are there telescopes, available for purchase, powerful enough to see the flag on the moon?
gpt
Nope. Even the largest telescopes on Earth couldn't resolve it, even if you completely ignored the atmospheric distortion that can only be removed imperfectly. The E-ELT, at 39 meters wide, will have a diffraction limit at the bluest wavelengths the eye can see of 2 milli-arcseconds, while the flag, if it were the size of a person and laying flat instead of being edge-on from the top, would still only be 1 milli-arcsecond in size from Earth. The biggest research telescopes being *planned* can't see it, even in the absurdly optimistic limit of ignoring the atmosphere entirely. Nothing you can buy for backyard use is even going to be able to see the landing site, much less the flag. In your backyard, you're going to be limited to what the atmosphere allows you to resolve (called the "seeing") which in most decent places on the ground is probably around 2 arcseconds on a good night. If you go up to the top of a mountain in the best places in the world, it can be as low as 0.5 arcseconds with some reliability.