THE CASE FOR A LIQUID MIRROR IN A LUNAR-BASED TELESCOPE

I discuss the advantages that a lunar liquid mirror telescope would have over a conventional glass mirror instrument. The very high optical quality obtainable with liquid mirrors and their simplicity make them excellent candidates. The mass of a liquid mirror is an order of magnitude less than the mass of a glass mirror of equal size, resulting in substantially smaller shipping costs. Because liquid mirrors are so simple, a 4-8 m diameter lunar liquid mirror telescope should be feasible at relatively low cost very shortly after the establishment of a lunar base, and even larger mirrors should be feasible at later dates. I discuss some practical considerations. In particular, I consider mercury and gallium (and its eutectic alloys) mirrors, concluding that gallium is preferable to mercury because of its higher reflectivity, lower mass and greater ease of wetting.