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As I understand it, the moon makes for an ideal location for a telescope because it offers environmental factors that are unlike anything achievable on earth: A lack of atmosphere, light pollution, and electromagnetic sources all make for ideal conditions. Is this accurate?

Theoretically, would there be a significant improvement in observability?

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    $\begingroup$ Thank you for the answers so far. I did exclude the financial implications involved with achieving this. This was intensional in order to focus on the practical advantages of this specific project over what is achievable on earth. I also excluded the benefits provided from attempting an off earth construction. Please keep sharing all your thoughts.Thank you. $\endgroup$ – PV22 Apr 17 '16 at 8:15
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    $\begingroup$ Again, thank you for the answer. Please again take note, I am asking whether a lunar telescope would provide better better observability that a similar device on earth. Is that improvement a significant degree better than what exists on earth? $\endgroup$ – PV22 Apr 17 '16 at 18:56
  • $\begingroup$ Link to similar thread: "Would placing an x-ray telescope on the surface of the moon be a good idea" $\endgroup$ – PV22 Apr 17 '16 at 19:15
  • $\begingroup$ Related article. businessinsider.com/… $\endgroup$ – PV22 Jul 15 '18 at 12:49
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As stated, the answer to the question has to be yes, a telescope on the Moon can have significant advantages over a telescope on Earth, because of Earth's atmosphere. That's why we have space telescopes.

However that is the wrong question. The real question is what advantages, as well as disadvantages, does a telescope on the Moon have over a telescope somewhere else in space, e.g. in Earth orbit or at a Lagrange point?

Overall, a telescope on the Moon is a terrible idea. First off, thermal control would be a nightmare. There are two week days and two-week nights, misaligning everything you might try to align in a telescope and with the swings making it extremely difficult to keep infrared sensors at cryogenic temperatures. Second, for the same reason, you only have solar power half the time. So you need to have enough batteries to stay alive for two weeks, or nuclear energy! If on batteries, you will want to conserve power exactly when you'd like to be observing more. Which brings up visibility. You can only see half the sky, and your telescope keeps getting turned towards the Sun every month whether you want it to or not. Which brings up pointing. You now have the Moon's gravity to deal with when turning your telescope. In space you have only your own inertia to deal with. Furthermore it will need to deploy itself in lunar gravity as opposed to zero gravity. And then there's the dust. Dust that gets kicked up by impacts and electrostatically, eventually covering your optics with a layer of crap.

You mentioned in a comment excluding considerations of cost, but you can never exclude that. Landing something softly on the Moon is hugely more expensive, in terms of mass and money, than putting it at a Lagrange point.

Should I go on?

The only conceivable advantages I can come up with are:

A. You have a stable surface in a vacuum on which to build a large interferometer,

B. Radio silence on the far side (but adding the complexity of requiring a relay orbiter to get the data back), and

C. Availability of raw materials.

For A, we can do the same thing in free space with precision formation flying, and then the horizon of the Moon doesn't limit your baseline distances.

For B, a radio telescope would get excellent isolation from Earth radio transmissions. However it seems that just putting your radio telescope on Earth in a valley with some mountains around you, and maybe some radio silence laws, works just dandy. You don't need the expense of a space-borne radio telescope (where such telescopes need to be ginormous.)

For C, you could extract materials from lunar regolith to make your mirrors. You could do the same from an asteroid more easily, with a wider range of asteroid types to choose from, and in lower gravity.

So yes, it would be better than Earth (for optical), but much, much worse than simply putting your telescope in space somewhere which is cheaper and easier.

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    $\begingroup$ And another point; the Moon has relatively significant gravity. I don't know how common lunar surface impacts are, but I dare say they do happen from time to time even these days. While you'd have to be pretty unlucky to have an impactor hit your telescope specifically, if it does, it's unplanned game over until you spend the money on a replacement. In orbit, or at a Lagrange point, the same holds true but the risk of the two objects intersecting seems to me to be significantly reduced. Of course, Apollo and friends faced the same risk, but for a much shorter duration surface stay. $\endgroup$ – a CVn Apr 18 '16 at 14:29
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    $\begingroup$ True as well. At some size, you're getting hit by micrometeorites all the time. The consequences depend on the sensitivity of the optics to that sort of thing. Assuming that a hit only makes a tiny ding and doesn't propagate to a crack, then I think that the effect on the images would not be noticeable until you had a lot of hits. The image is not focused at the surface of the mirror, so the effect of the ding would be spread over pretty much an entire focused image. $\endgroup$ – Mark Adler Apr 18 '16 at 15:15
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    $\begingroup$ Right, micrometeorites are an entirely different ball game. I was thinking more about impactors of sufficient mass that on impact they have the inertia to actually damage the equipment, including at least cracking glass. $\endgroup$ – a CVn Apr 18 '16 at 15:28
  • $\begingroup$ These are ]environmental factors that need to be addressed in order to further a space program. I would think it best to encounter them in a relatively close to home situation first, However, this is out of scope for the original question. $\endgroup$ – PV22 Apr 19 '16 at 3:50
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    $\begingroup$ 1. Any satellite will be built in perma-shade and probably shielded with regolith. $\endgroup$ – ventsyv May 7 '16 at 3:56
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That depends on what kind of telescope we are talking about.

Disclaimer: I am NOT an astronomer. I'm just a nerd who happens to provide computer security help for some awesome telescopes, and has seen them up close.

For a radiotelescope, I believe that there would probably be an advantage to running it on the moon. There would also be a number of logistical disadvantages (getting someone out there to repair the thing is suddenly expensive and time-consuming, for example). However, the radiotelescopes here on earth do a lot of work filtering out terrestrial signals, and getting them even a little further away from those signals (it's really only a little in astronomical scale) could make that easier. Worth all the money and logistical overhead? Maybe not...astronomers have gotten good enough at this that the optical telescopes around the radio telescope installations on Mauna Kea only get a modicum of grumbling over their wifi access points, and the dining hall shared by the 13 observatories is equipped with a microwave.

For an optical telescope, we'd have to be building the thing at a MUCH higher focal length, resolution, and sensitivity than we are doing now to get an advantage by placing it on the moon. I recently got to play around (well, not play, I was working) on Mauna Kea in Hawaii, and got an up-close look at the Gemini Observatory there. At about 14,000 feet above sea level, the air is pretty thin, and they have a system for sampling atmospheric disturbance between the telescope and bright objects so that that distortion can be compensated for when viewing less-bright objects near that field of view. Light pollution really isn't an issue atop Mauna Kea. It's high above and miles away from the nearest homes and businesses. The visitor station is about 7k feet below the summit if I recall correctly, and closed at night. I believe that the area around and over the observatories is a no-fly zone as well. Looking at blown-up photos of the same deep-space objects taken by Gemini and by Hubble side by side, I couldn't find a difference in clarity.

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Mark asked the correct question, which is how would it compare to a satellite around Earth, or other location in space. I'm going to offer the only 2 suggestions that I've heard of that make sense.

Radio Telescope- On Earth is is virtually impossible to obtain pure radio silence. Being an Amateur Radio operator, I can attest to that. The best that one can do is to have an area very isolated, preferably with mountains around it, but even that is difficult, and doesn't work for some bands. For RF bands that are affected by the atmosphere it is virtually impossible to obtain complete radio silence on Earth. The far side of the Moon does offer an attractive proposition for such an observatory, although as noted, it does have some serious difficulties.

Infra-red. There are a few craters near the poles which are in perpetual shadow. These could make for an excellent infra-red observatory. The biggest problems are power, and the fact that you are limited to only the southern half of the sky (Really less than that) by such a telescope. Still, it could work conceivably.

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  • $\begingroup$ Or limited to the northern half of the sky... $\endgroup$ – kim holder Apr 18 '16 at 14:25
  • $\begingroup$ Fair enough, but the main crater of interest is at the southern part. There would be virtually no chance to observe the ecliptic in either case. $\endgroup$ – PearsonArtPhoto Apr 18 '16 at 14:29
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This discussion is missing a lot of the main advantages of a lunar telescope.

This is mainly from the telescopes on the Moon section of my Case for Moon First (except I forgot to mention interferometry there - will do with next update).

The dust can be dealt with, for instance by making a region around the telescope into glass, which is easy to do on the Moon as use of a microwave turns the regolith into glass as easily as you boil a kettle. Unlike Mars, there are no dust storms to deal with. Just electrostatic elevation of the dust. See Lunar Glass

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Theoretically, yes it would improve our scope of observation if we use a lunar telescope.

But I believe, the cost of doing so would significantly outweigh the advantages it will have than launching telescopes in low Earth orbits.

Plus, moon is a heavily cratered body. If we were to position a telescope on the dark side of the moon ( the face we do not see ), it will increase the chances of the telescope being damaged. If we position it to the other part of the moon, we would not have a bigger horizon on our plate, thus reducing the productivity of it.

Then, we have the problems with managing the telescope remotely. The Hubble telescope itself had to be repaired/upgraded on several occasions and these maintenance missions are expensive and dangerous, to both the telescope and astronauts.

And again, having a telescope orbiting around does not really hinder our observations since they are out of most of Earth's atmosphere.

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