How many power would a telescope need to be for us to see the junk we left on the moon?

Question

How many power would a telescope need to be for us to see the junk we left on the moon? I realize the junk our astronauts left on the moon is pretty small so today's telescopes can't see any of it. What kind of magnification would we need to see that stuff from Earth or low Earth orbit? Assume a 6MP camera.

Answer 1

In order to determine this, we need to look at size and distance.
Size of the largest object left on Moon was probably the lander at approximately 12 feet across. Distance to the Moon is approximately 238,000 miles. If a telescope could magnify 238,000 times, that would make the 12ft lander look like it was only 1 mile away. Since it would be possible to see a 12ft object approximately a mile in the distance, a somewhat lower magnification would do. However, the required magnification would still be somewhere between 120,000 and 180,000. In other words, far beyond anything possible on Earth or even low Earth orbit.

Answer 2

Working off Otis F's post, which is the most accurate, we'd need an aperture (mirror diameter) of about 41 yards. The current largest telescopes are well under that range, around 10 yards, and hence have insufficient resolution. Resolution and magnification are not the same thing. You can use any old telescope and magnify 180,000x but the image will be a blur. Resolution is what provides meaningful information inside the magnification.


The arguments about atmospheric degradation of the image are true to a point. The use of *adaptive optics* greatly improves the performance of earth-based telescopes. The effectiveness of this technique varies with the specific technique used and the *wavelength* of the light that is being sought (tends to get better into the red end of the spectrum).

A telescope of sufficient aperture and designed with the latest and greatest adaptive optics might be able to image human artifacts on the moon. But these telescopes have not been built yet.

In any case the core answer to this question lies in the concept of resolution, which most people know about from their digital cameras. You can blow up an image and still have it sharp--sometimes amazing details can be seen, like you read a small label on someone's clothes that barely shows at "full scale." As you zoom in using the computer, the image stays sharp. Zooming in is MAGNIFICATION.

But when you get to the limit, you start to see pixels (squares from the camera sensor). This is the limit of the camera's RESOLUTION. *Magnification* can only help you see things that are *already there* because there is good *resolution*. When you have good *resolution* you can expand the *image scale* and see more. If the *resolution* is insufficient the information is *never there to be had*. There are marvelous pictures of the moon from many telescopes, but no matter how much you MAGNIFY them, the information about where the lunar module is will never there in the image. This is established optics known to every optometrist who makes an eyeglass prescription.

By putting a big telephoto lens on the camera you can improve the resolution, but if you take that image, and blow it up, eventually you get the pixels again, the limit of the telephoto lens's *resolution.* As has been discussed, you'd need about a 41 yard (by diameter) telephoto lens to get your camera to resolve features ten or twelve feet in diameter on the Moon. Since such huge telescopes are built to photograph the most distant galaxies in the universe, I am skeptical that it would ever be pointed at the moon, as cameras built for photographing galaxies might have a hard time with the brightness.

Hope that helps. The difference between resolution and magnification is the biggest obstacle that those of us who use telescopes a lot face in communicating with the the public. The view of Saturn in my 14 inch telescope at 98 power magnification is much better than in my 4 inch telescope at 189 power. There is more in the image because of superior resolution.

Answer 3

It isnt a question of the power of the telescope, Its a matter of the clarity of the atmosphere.
If you use a telescope to look at a distant object on a sunny day you will find that more magnification doesnt help you see the object any better. The more magnification you use, the more you can see that heat haze wont allow you to see any better. On a nice cool clear night the haze is a lot less but there is still a bit. This residual haze is enough to prevent you from seeing anything that small. That is why they put a telescope in space.
One of the moon missions did leave a reflector on the moon.
This enables you to point a powerful laser (or maser?) pulse at the reflector and detect the returning pulse. It is this system that tells scientists exactly how far away the moon is and enables them to measure how the distance changes.
If you have the right equipment you can detect this reflector so in that sense you can "see" one piece of "junk"

Answer 4

It's not so much a question of magnification as of resolving power, and the artefacts left on the Moon (I certainly wouldn't call them junk!) are just too small to be seen at that distance with any telescope on Earth, or even the Hubble. The blast scars from the LEM's takeoff have however been recorded by satellites orbiting the Moon, just as the Mars Rovers have been imaged by satellites orbiting Mars.

Answer 5

It is not possible to build a telescope with that much magnification and resolution which will work on the surface of the Earth. Earth's atmosphere places a haze penalty onto all observations made here. It is the very reason that a telescope was moved out into space (Hubbel Space Telescope).

Answer 6

I guess that would depend on how big the "junk" is. For the sake of argument, let's say it is 10 feet across. Then, being able to see this junk would be like being able to see a penny 1,500 miles away. No, there are no telescopes close to having this kind of magnification.

Answer 7

The Advanced Camera for Surveys on board the Hubble Space Telescope has a resolution of .03 arc seconds. At a distance of 240,000 miles, the largest objects left behind by the Apollo program are .002 arc seconds wide. Therefore, the HST would have to be 15 times larger in order to photograph them. Even then, it would look like a dot. And, if the HST were 15 times larger than it is, we would be able to launch it.

Answer 8

Probably it would not be possible to build a telescope large enough on earth to do that. However, it would be possible to capture an image that shows a specular reflection off some of the landers left on the moon. It would be a bright (relative to the surface of the moon) point of light. I am very surprised that hasn't been done by now.

Answer 9

another problem with capturing a photo of the moon (even of just the moon, not the junk on it) is that the moon is moving quite fast and you usually have to take these photos in the dark. This requires a longer exposure, and you usually need something to track the moon as it moves, otherwise the photo comes out blurry. Using magnification (if it's even possible to get enough magnification to see the junk in the first place) would require something extremely precise to match the movement of the moon, especially since magnifying the image also magnifies the movement, so even a tiny movement results in a huge shift in the field of vision

so capturing a photo like this would be nearly impossible, if not impossible!

Answer 10

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