Optical tests of a 3.7-m-diameter liquid mirror: behavior under external perturbations

We built and tested a 3.7-m-diameter liquid mirror that rotates on a ball bearing. Although the ball bearing is of a poor quality, the mirror is surprisingly good for one that comprises 1-mm-thick mercury layers. We found no evidence of the strong astigmatism that might have been expected from Coriolis We did not detect effects of turbulence might or vibrations for thin mercury layers, illustrating layers. forces. We did not detect effects the necessity of using thin layers: for layers much thicker than 2 mm. Large liquid mirrors would have had unacceptable optical qualities (C) 2000 Optical Society of America OCIS codes: 110.6770, 230.4040, 120.0120.