According to Wikipedia, Luna 15 crashed a few hours before Eagle lifted off from the moon, and since it crashed North-east of the landing site, it must have overflown them. Would any of the crew have been able to see Luna 15, perhaps the deorbit burn or debris ejected into space from the crash itself?
On Earth, most of visibility of objects coming from space is created by interaction with the atmosphere. As Moon has no atmosphere, an approaching space object would appear in a similar way to how on Earth we perceive orbiting objects: light reflected from the Sun at best. That is, under conditions that the object is large, reflective and properly positioned relative to the Sun and the observer.
You can't notice Soyuz boosting ISS so the deorbiting burn would be similarly unnoticeable. As for ejected debris, without an atmosphere to burn in, they were small and some of them charred, so even less visible than Luna in one piece.
Apollo crew would be able to notice Luna 15 only if they knew when and where exactly to look for it. Even then, if the Sun was in "wrong" position, they'd have very little chance of seeing it coming.
It's unlikely. They made no report of seeing it, although it was mentioned as a news item at several points during the mission. The sky is big, the moon's surface is big, rockets are fast, hypergolic propellant rocket plumes are very faint.
Unlikely. Luna 15 left earth a little before Apollo 11 did. Although the "Cold War" was in full swing with intense rivalry, NASA took the then very unusual step of asking its enemy the Soviet Union if Luna 15 was going to interfere with the Apollo 11 trajectory. The Soviets, equally unusually for that time, replied it would not. Possibly the recordings of the Apollo 11 mission and the news items that went with that, will confirm what I recall from being there and hearing that mission "live", that the astronauts reported that they never saw the Luna 15 at any time.
So of course my reference for the above information is "me", young adult alive at the time.
I just saw a documentary about it. According to it the Apollo astronauts did know Luna 15 was near them and I think it said some of the astronauts finishing their moon walk and getting ready to leave saw it flying around as it did something like 42 orbits Of the moon while our astronauts were doing the walk. I’m not sure if they saw the crash but they def saw the spacecraft orbiting around them which just had to be crazy i imagine. And as someone kinda mentioned the US and USSR even talked to each other about their missions. They both knew it was happening and made plans so their radios and channels wouldn’t interfere with each other’s and to make sure the trajectories were not going to interfere with each other’s either. It was pretty cool for them at that time to put the Cold War on the back burner so to speak. One famous cosmonaut said the whole USSR space program for one moment forgot we were different countries in a war and they all cheered and applauded our astronauts landing on the moon as one human race Rather than Americans vs. Russians.. which if just awesome 👏
Almost certainly not.
First of all, only very bright stars were visible, when standing in the shadow of the LEM. The size of it was quite small, so most likely it would be too dim to view.
The deorbit burn took place at 15:47 UT on 21 July 1969. It crashed about 17° north latitude and 60° east. The difference in longitude is about 37 degrees, meaning it wasn't overhead during the burn.
It could have happened, but it would have required a dedicated look, or extremely good luck. As there is no record of such having happened...