Eli5 why can’t telescopes see landing zones on the moon?

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I was gonna prove to my co-worker we did in fact land on the moon, but Looking up how to see the landing sites with a telescope said it is physically impossible (improbable). An explanation went with it but… Yeah… It’s why I’m here.

I know we have a lunar satellite that can show it, but I’m prepaid for inevitable ” computer graphics recording”

Edit. Maybe I’ll just ask for someone to explain “Dawes limit”

In: Physics

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There’s an easier way to do it than looking with a telescope, because NASA literally planned to have a way to easily confirm it and do experiments by figuring out the distance to the moon and having a way to reflect back.

They placed essentially a series of 5 mirrors on the moon by different missions, you can shoot light/laser at any of them and it reflects back. The use of mirrors and reflections is standard stuff in astronomy and optics. Astronomers do use these reflectors too!

To actually see the landing sites, you’d need a huge telescope with a lot of fancy equipment on the ground, or more likely, one in space. The moon is far and seeing that good of resolution on a tiny thing like a landing site youd need an enormous telescope. Telescopes are great for seeing big objects, but when you need to see small, and far away, the size necessary to do that becomes much much bigger

The moon is nearly 400,000 km away. The landing site is very small. In order to magnify something very small from such a far distance away, you’d need an absolutely massive lens. There isn’t a telescope on Earth that’s large enough to do it.

If your coworker thinks the moon landing was faked in spite of the overwhelming evidence that it happened, it’s unlikely that additional evidence is going to make him realize that he’s wrong.

They’re too small to be visible with buildable telescope

A telescope is limited in how precisely it can capture detail. When you have a point light source it ends up kind of looking like a little blob, and if you put two close to each other they can appear to be a single blob rather than the two blobs. How close you can get them(in visual angle) depends on the diameter of the telescope and the wavelength you’re working with

The base of the lunar lander is only about 4 meters in diameter, the legs add another 5 but they’re going to be too skinny to help you here. 4 meters, at a distance of 400,000 km is 10^-8 radians which is really really tiny.

Your telescope has a resolution of ~1.22 * (wavelength)/(Diameter of telescope) so assuming green light (500nm) to even pick out a single spot 4 meters wide on the moon 400,000km away you need a telescope with a diameter of 61 meters. If you want it to be 2×2 pixels then you need 122 meters

This is a hard physics limitation due to the wave nature of light, and doesn’t include the atmosphere fuzzing up your results even more.

This is why we don’t just use satellite imagery of Earth. If you want good details you need to combine aerial imagery either through photography planes or unmanned drones. Being wayyy closer to the target lets them use far smaller lenses and capture better images.

Hi 🙂

> telescope

You can’t because the moon is really, really far away.

In models, the moon’s always this big ball orbiting our big ball. But it’s more like a tiny pebble that’s really, really far away.

(To get a sense of how far and small the moon is, check out [If the moon were only one pixel](https://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html)).

To see details and the remains of the landing site, you’ll have to magnify several thousand times, and need a telescope aperture almost half a mile wide to resolve it as a dot. Regular telescopes can not resolve that amount of detail.

For something 0.5mm / 1.6ft wide filling the view in your telescope’s eyepiece, you’d need over 700,000,000x magnification and several miles of aperture. Our earth’s atmosphere usually limits you to around 200x magnification. A bit more on a good day, a bit less on a bad day. Even when atmopsheric seeing is excellent, you may only go up to 400x, 500x.

 

Even Hubble can not resolve details on the moon due to the required aperture.

Older post of mine with some explanations, math: https://www.reddit.com/r/explainlikeimfive/comments/otj55t/eli5_which_sizetype_of_telescope_could_ideally/h6vscmo?utm_source=share&utm_medium=web2x&context=3

The reason why we can resolve planets, clusters, nebulae and galaxies is that they are really, really huge. Even though they are far away, you can see them in lower magnifications. The apparent size of the Andromeda Galaxy is way larger than our moon. But it’s much fainter. So without a telescope, you can only see it from very dark places.

 

The only way you can prove we’ve been up there, are the mirrors left behind by the astronauts. You shoot a laser and measure the time the signal requires to get back. But you need a very powerful laser, and a very sensitive receiver.

 

> prove to my co-worker

If recordings, astronauts and literature can’t, you will probably not be able to. It’s sad that people will rather believe the flawed arguments on social-media. Often you just solidify their believes if you try to argument. Going from debunking one theory to the next, with no end in sight.

Even if you had a telescope to show it, some weirdo on the internet will come up with some theory why it’s just a hologram or something.

There’s a property with optics where the ability to resolve two points a given distance apart is dependent on:

1. The distance apart the objects are (or in the case of a single object how wide it is).
2. The distance away the object is.
3. The width of the telescope aperture (opening)
4. The wavelength of light being observed

If the distance is too large for the telescope diameter when using visible light the path of the light waves gets bent by the process of passing though the telescope opening, and that bend is so much the light from one object overlaps the light from the other, making them appear as a single blurry object.

The further the object is away the bigger the telescope you need to avoid this effect.

For the moon landers – the their size combined with their distance you’d need a telescope hundreds of feet across. This is significantly larger than any telescope ever constructed and would be an absurd engineering effort. Look up the giant Magellan telescope project – a fraction of the size of the one required to see the moon landers – for an idea of the effort required to build a telescope big enough.

Basically, it’s too small to see. We can see mountain ranges, and craters…but even the best earthbound telescopes aren’t good enough to see a landing site as anything more than a single darker pixel or two.

Essentially your typical hobby telescope is too small to see anything that humans left behind on the moon. We’ve left behind the Apollo lander base (legs) and the lunar rover as well as a few other objects.

To explain why your usual hobby telescope is too small is that you need three things to take a good image. You need a good level of magnification, a high aperture for sharpness and a large area to reflect the light.

The moon is about 380,000 kilometres from earth and has a visible surface area of about 20 million square kilometres, which is roughly the same as the whole of North America. Now try finding an object about 5 metres or so across somewhere in an area that size. Yes you can look up the coordinates of the object and then get your telescope to find it but that’s not the point.

To make sure you have a telescope to meet those three criteria you can have a large telescope with the correct set of lenses for magnification. The size of the telescope can meet the aperture and the large light collecting area requirements. However, a telescope large enough will need to be metres across to meet those requirements. This will make it very expensive and very difficult to make for the tolerances needed for an accurate image.

However, scientists have found that the can meet those requirements by using multiple smaller telescopes far apart from each other. You can through this principal effectively have a telescope with a light collecting area that is kilometres wide by using spaced out telescopes. Although the issue this now faces is not having a large enough collection area but this can be overcome by increasing the exposure to create the image.

TL;DR the objects are too small and too far away for your hobby telescope to see because they are too small