Optical tests of a 2.5-m-diameter liquid mirror: behavior under external perturbations and scattered-light...

Interferometric tests of an f/1.2, 2.5-m-diameter liquid mirror show rms surface deviations of ~lambda/20 and Strehl ratios of the order of 0.6, which show that it is diffraction limited. The mirror is certainly better than what is implied by the data because of aberrations introduced by the auxiliary testing optics. We made detailed studies of the scattered light of the mirror. We studied the behavior of the mirror under external perturbations. We reached an important milestone because we now have a good understanding of liquid mirrors.