[1]https://www.popularmechanics.com/space/moon-mars/a34714863/liquid-mirror-tele
scope-on-the-moon/

   I will be able to provide them with the material which makes up the
   liquid mirror:. It will use isotopes to keep the mirror liquid, even in
   the cold.

References

   1. https://www.popularmechanics.com/space/moon-mars/a34714863/liquid-mirror-telescope-on-the-moon/