Goal of lunar liquid telescope not so distant – CNN.com
WASHINGTON (Reuters) — Scientists have taken a giant leap toward making possible the dream of building a powerful telescope on the moon that could withstand even the harshest of lunar conditions.

Writing in Thursday’s edition of the journal Nature, they said they coated a special type of liquid surface with a layer of silver to make a highly reflective mirror like one that could be used in any future, moon-based telescope.

This isn’t remotely a new idea, but what is new is that they’ve done some actual research and experimentation with materials that could be used for this sort of telescope.

Now, what they don’t tell you in this story is that liquid mirror telescopes must remain perpendicular to the gravitational field they are in, so they can’t “scan” the sky like a conventional hard-mirror telescope. They also can’t be used in microgravity (like the Hubble or proposed Webb telescopes) because the parabolic curve of the liquid itself depends on the mirror being spun in a significant gravitational field. So that means that it has a very limited view of the sky, essentially straight up from wherever it is built.

However, telescopes that can only look straight up still have a lot of value, as shown by Puerto Rico’s Arecibo radio telescope, which is the biggest on earth and is built into the ground in Puerto Rico. Even if you are constrained to a five-degree strip of the heavens, there’s still a lot to see in that strip. And believe me, there would be a lot of wrangling over exactly where to build the thing so that the “best” five degree strip of the sky would be visible to it.

My attitude is “why limit yourself to a 100 meter telescope?” I still think there are ways to build a much larger telescope and make it space-based for the most flexible possible use.