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Even Earth's mightiest telescopes aren't up to the task of imaging Apollo lunar landing sites. A lack of resolution is the biggest reason why:
Back in the early 2000s, when I was butting heads seemingly every week with people who believed the Apollo moon landings were faked, such individuals would pull out an argument they thought was their ace in the hole: If NASA's Hubble Space Telescope is powerful enough to see the intricate details of distant galaxies, why can't it see the Apollo astronaut boot prints on our own moon?
Like most conspiratorial thinking, this argument seems persuasive on its surface but falls apart under the slightest scrutiny. Those taken in by it have a misunderstanding of two things: how telescopes work and just how big space is.
Many people think a telescope's purpose is to magnify images. Certainly manufacturers of inexpensive (read: cheap) telescopes love to market them as such: "150x power!" they print in huge lettering on the box (along with highly misleading photographs from much bigger telescopes). While magnification is important, a telescope's real strength is in its resolution, however. The difference is subtle but critical.
Magnification is just how much you can zoom in on an object, making it look bigger. That's important because while astronomical objects are physically big, they're very far away, so they appear small in the sky. Magnifying them makes them easier to see.
Resolution, on the other hand, is the ability to distinguish two objects that are very close together. For example, you might perceive two stars orbiting each other—a binary star—as a single star because they're too closely spaced for your eye to separate. You can't resolve them. Looking through a telescope with higher resolution, however, you might be able to discern the separation between them, revealing that they are two individual stars.
But isn't that just magnification, then? No—because magnification only makes things bigger! This is easy to demonstrate with a photograph: you can zoom in on the photograph as much as you'd like, but past a certain limit, you're just magnifying the pixels, and you can't get any more information out of it. To break through that wall, you have to gain resolution rather than magnification.
[...] At its best, Hubble's resolution is about 0.05 arcsecond—a very tiny angle! But how much detail it can see in real terms depends on the target's distance and physical size. For example, 0.05 arcsecond is equivalent to the apparent size of a dime seen from about 140 kilometers away.
That brings us back to the conspiracy theorists and their gripe about spotting boot prints on the moon. Galaxies are typically tens of millions or even billions of light-years from Earth. At those distances, Hubble can resolve objects a few light-years across—tens of trillions of kilometers—at best. So while it looks like we're seeing galaxies in great detail in those spectacular Hubble images, the smallest thing we can see is still tremendously huge.
Meanwhile the moon is only about 380,000 km from us—and from Hubble. At that distance, Hubble's resolution surprisingly limits it to resolving objects no smaller than about 90 meters across. So not only can we not see the astronauts' boot prints in Hubble images but we also can't even see the Apollo lunar landers, which were only about four meters across!
(Score: 5, Insightful) by Ingar on Monday September 02, @01:58PM (5 children)
When talking telescopes, it is one of those typical layperson questions: "what's the magnification?"
In this context, magnification is a somewhat useless metric. In astrophotography, resolution is indeed what matters.
Because of our atmosphere, the limit for earth-based observations is around 1 arcsecond.
My own telescope setup sits at 1.6 arcseconds/pixel, Hubble's resolution is 32 times better.
The resolution is a combination of focal length ( "magnification" ) and the physical dimensions of a sensor pixel.
Understanding is a three-edged sword: your side, their side, and the truth.
(Score: 3, Insightful) by Anonymous Coward on Monday September 02, @02:20PM (2 children)
The resolution is also limited by the size of the telescope aperture. Diffraction from the telescope opening adds unavoidable blur, which is smaller as you increase the telescope aperture (the article touches on this and talks about the wavelength dependence as well). So even if you had no pixelated detector on the backend, you are still limited by that.
(Score: 3, Interesting) by mcgrew on Monday September 02, @02:55PM (1 child)
...which is smaller as you increase the telescope aperture...
And with that, the larger the aperture, the shallower the depth of field.
Poe's Law [nooze.org] has nothing to do with Edgar Allen Poetry
(Score: 5, Interesting) by Ingar on Monday September 02, @04:47PM
Since you're effectively focusing at infinity, that isn't really an issue.
Understanding is a three-edged sword: your side, their side, and the truth.
(Score: 2) by mcgrew on Monday September 02, @02:52PM (1 child)
Because of our atmosphere...
Someone is bound to ask "then why can we easily see people in satellite images?"
The answer, of course, is that the moon is a hell of a lot farther away than an artificial satellite.
Poe's Law [nooze.org] has nothing to do with Edgar Allen Poetry
(Score: 5, Interesting) by VLM on Monday September 02, @03:22PM
Generally you can't see people from space, with weird exceptions.
There's a "famous" ESA photo from awhile ago but not too long ago (some years but not some decades), where they had a very-low earth orbit satellite with a very small scope on it, and "a thousand" ESA employees stand in a field in the shape of the ESA logo (which IIRC is super lame, like lower case serif letters acronym) and you can read the logo but you can't really tell its people it could have just been plants or paint. Unless you were told that was made by 1000 people you would assume its something like a flower-bed or mosaic art from an extreme distance. Like not being able to image the individual pixels in this word: esa but being able to read and recognize the "esa".
The three letter agency people have had VASTLY larger classified satellites and they can supposedly resolve people. Note there's a big difference between you expect to see people there and there's a single pixel dot so you say its a picture of a person (a guard at a gatehouse, perhaps) vs a zillion megapixel glamour photo of a model which is somewhat harder to accomplish optically.
Its fair game to take photos of satellites to compare looking the opposite direction and its much cheaper to put a telescope in my backyard than into orbit; its VERY hard for an amateur to get a photo of the ISS unless you are previously told what you're looking at and you're not going to see astronauts smiling and waving or possibly mooning us, at best if you know the ISS you'll be able to ID the pattern of solar panels and radiator panels as being the ISS. Obviously, the air force has much better satellite imaging equipment to look at foreign countries military sats, but its "non-trivial" to get a good pic of a human sized satellite from the ground.
(Score: 4, Interesting) by VLM on Monday September 02, @03:09PM
Here's a pretty good EE analogy:
optic diameter, size, sets the signal to noise ratio.
The shape of the optic (magnification) sets the gain.
From playing with amplifiers we "all know" that if you have a small weak noisy signal then turning up the gain (amplification, magnification) all you get is a loud noise, not a clear noise.
People who've never used a scope (people buying a scope for a kid, perhaps) think all the money in a scope is in the magnification or gain, but actually, all the money in a scope is in the diameter or SNR or resolution.
Now what would be interesting is "how close do you have to be?" Its generally accepted that a NSA satellite from the 80s deployed from the Space Shuttle bay could under absolutely ideal conditions with a lot of good luck probably get a license plate correct or at least not too wrong. Also its unclear what they mean by image the plate; there's a single pixel indicating there is or is not a plate installed on the car, or are they imaging the screws so they can tell if I have a standard or Philips screw holding the plate to the car? So, a somewhat smaller scope in orbit around the moon should easily be able to image the landing sites, probably.
Another novelty is indirect proof. It would be beyond trivial to take a zillion photos around sunrise and sunset of very long shadows from very short lunar things in the region of the landing, and do an annoying amount of image processing to generate a 3-d model of the landing site based upon zillions of different shadow images, although it only exists in the equations there's no single photographic shot showing more than some strangely shaped shadow blotches. At the instant of sunrise, a "short" flag has an infinitely long shadow, if the surface of the moon were perfectly flat (which it is not). Like a MRI or CAT scan but using shadows.
A final novelty would be some kind of scintillation study. In theory, the shiny bits should be ... shiny, even if you can't resolve the image. Imagine a pile of dominos laying in my backyard, even if you can't image them, sometimes the sunlight will be very bright when the angles are "just right" and you could generate an elaborate model of the pile of shiny dominos based on the number, timing, and angle of reflections, even if you couldn't resolve the image of the dominos. I know there's laser retroreflectors on the moon and I know if you blast the F out of the site from earth you can get "some" photons back to the earth and they've been doing that since the landings. However, I wonder how things are in 2024... just how small of a scope would you need to detect the standard deviation of light intensity from a single pixel where the landing is supposed to be is just slightly off from all the nearby pixels? I'm not talking about directly imaging, or even 3-D modeling, just and anomaly in the light intensity showing there's obviously a mirror or gold foil thermal insulation or something down there.
(Score: 5, Interesting) by dx3bydt3 on Monday September 02, @05:03PM
To resolve something which is recognizable as a boot print, at the perigee distance to the moon you need a telescope that can resolve 1.7x10^-4 arcseconds.
That would require an aperture of 750m.
If all you wanted to do was to resolve a blob and distinguish it to be roughly boot shaped you could get away with just 0.006 arcsecond resolution, to get you down to roughly 10cm resolving power.
That takes just 25m minimum, which surprisingly is not that far out of reach right now. It's probably still cheaper to send a smaller scope to the moon though.
If you launched a Hubble sized scope into the same orbit around the moon as the Lunar Reconnaissance Orbiter, (20km perigee) that'd be able to resolve boot prints.
(Score: 4, Touché) by ChrisMaple on Monday September 02, @09:40PM
Read up on the Rayleigh criterion and understand it. Then do the math.
(Score: 1) by pTamok on Monday September 02, @11:03PM
While you'd need an infeasibly large aperture telescope to image the bootprints on the Moon, you can interact with a human-made object on the Moon: the Laser Ranging Retroreflector [wikipedia.org]
It's pretty interesting: Space.com (11 July 2019): Why Is the Apollo Reflector Experiment Still Operating, 50 Years Later? [space.com]
Apache Point Observatory Lunar Laser-ranging Operation [wikipedia.org]
List of retroreflectors on the Moon [wikipedia.org]
(Score: 3, Insightful) by bzipitidoo on Tuesday September 03, @12:30AM (2 children)
Suppose we did have a telescope that could resolve the moon landing sites. The hoaxers would just claim there is some other fakery going on. Nut job conspiracy theorists' problem is not the thing they profess to disbelieve. They have other things going on in their heads.
(Score: 2) by driverless on Tuesday September 03, @02:29AM
Obligatory link to the faked moon landings sketch [youtube.com].
(Score: 2) by Freeman on Tuesday September 03, @05:29PM
I know the moon landings were real, because how else would they have made "Iron Sky"? That documentary is epic.
Joshua 1:9 "Be strong and of a good courage; be not afraid, neither be thou dismayed: for the Lord thy God is with thee"
(Score: 2) by Username on Tuesday September 03, @04:51PM
On a Sony aIV with a Sony FE 200-600mm F5.6-6.3 G OSS lens, you can get good shots of the moon with detailed craters, get images of Saturn, and if you're lucky a satellite.
This thing is less than 2 ft long.
If you can only do the same on a telescope 50x the size, there is something wrong.