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This question already has an answer here:

Is it possible one day to see landing site flags on the Moon from Earth or from space without having to land using a telescope as technology progresses?

Highly Related: Were the Apollo lunar activities observed from Earth?

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marked as duplicate by Antzi, Jan Doggen, GremlinWranger, Manu H, DrSheldon Apr 17 at 11:52

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ Title and body don't match. $\endgroup$ – Antzi Apr 17 at 5:44
  • $\begingroup$ @Antzi fixed it thanks. $\endgroup$ – Muze the good Troll. Apr 17 at 5:53
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    $\begingroup$ Directly from the Earth, the answer is no, but as the answer says, we can see it from Moon orbit. $\endgroup$ – peterh says reinstate Monica Apr 17 at 6:58
  • $\begingroup$ Although the other question is related it is not a duplicate it is talking about something a 1969. Where mine is asking for current technology. $\endgroup$ – Muze the good Troll. Apr 17 at 15:55
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    $\begingroup$ The revision doesn't make the question better, imho. The fundamental physical problems stay the same, and everything else is pure speculation. Its already possible to see it from space, you just need to get into a lunar orbit - the lower the better you can see it. $\endgroup$ – Polygnome Apr 17 at 20:48
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I am not aware of an optical telescope capable of showing proof from earth. Part of the reason is the flags are pretty small and it's a very long distance. However, you can see the flags or what is left of them and the landing sites using images from the Lunar Reconnaissance Orbiter (LRO).

The LRO was able to use it's camera to document all of the Apollo landing sites. In 2011, Eric M. Jones collated the images to show the conditions of the landing sites and evidence of the condition flags was presented.

Apollo 11

Buzz Aldrin indicated he saw the flag knocked over on liftoff from the moon.

This quote was from the manufacturer:

Dennis Lacarrubba, whose New Jersey-based company, Annin, made the flag
and sold it to NASA for $5.50 in 1969, considers what might happen to an ordinary nylon flag left outside for 39 years on Earth, let alone on the moon. He thinks for a few seconds. “I can’t believe there would be anything left,” he concludes. “I gotta be honest with you. It’s gonna be ashes.”

Apollo 12

Apollo 12 flag

Apollo 14 and 15 had no evidence from the images of the flags. It was thought they may have been destroyed by the exhaust gases on liftoff.

Apollo 16

Apollo 16 Flag

Apollo 17

Apollo 17 flag

More Information

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  • $\begingroup$ Interesting, but not expolicitly answering the question. Yes, you can see a flag shadows from moon orbit, but the question was about the flag and about the observation source Earth. $\endgroup$ – Jakuje Apr 17 at 12:04
  • $\begingroup$ @Muse seems to think the moon landings were faked. I posted this to show there are photos of the landing sites. I'll add the fact you can't see them from the earth. $\endgroup$ – gwally Apr 17 at 18:36
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A flag would be about five hundred micro arcseconds. (about 1 meter, at around 375 Mm)

The Event Horizon Telescope has a resolution of about 20 micro arcseconds.

Therefore, EHT could resolve a flag on the surface of the moon if it were a radio source.

However, to view it optically would require around a 350 meter aperture. The largest 'single' telescope today is around 10 meters

The Cambridge Optical Aperture Synthesis Telescope (COAST) - the largest I'm aware of - can resolve to around 1000 micro arcseconds, so wouldn't be able to see a flag.

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    $\begingroup$ oops, previous answer was out by a $10^3$, changing the outcome. $\endgroup$ – JCRM Apr 17 at 9:02
  • $\begingroup$ hope it's not offtopic but would it be possible to couple optical telescopes in the same way the EHT did? $\endgroup$ – undefined Apr 17 at 9:58
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    $\begingroup$ That's largely what COAST does @undefined, except optically not analytically. To complicate things, one also needs to collect enough light to see it, so it would need a large collection surface, as well as aperture (even with long exposure times) $\endgroup$ – JCRM Apr 17 at 10:26
  • $\begingroup$ oh thank you, JCRM. I thought the COAST is only one large telescope and not many. Thank you :) $\endgroup$ – undefined Apr 17 at 10:30

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