Optical Tests of a 2.5-m diameter Liquid Mirror: Behavior under External Perturbations and Scattered Light Measurements

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