Liquid mirror telescopes: a progress report

We review the status of the liquid mirror project. Interferometric tests of a f/1.2 2.5-m diameter liquid mirror carried out with a scatterplate interferometer show Strehl ratios of order 0.6, close to the value of 0.8 usually taken to signify that diffraction limit has been reached. The mirror is certainly better than implied by the data because the interferograms were taken with 1/500 second exposures and the wavefronts therefore include the effects of seeing in the testing tower. Correctable small variations of the rotational velocity account for another substantial fraction of the deviations from a parabola. We have videotaped hours of interferogram and PSF observations that show that those we analyze are representative.

[1]  Gerard Lemaitre Various Aspects Of Active Optics , 1989, Defense, Security, and Sensing.

[2]  J. C. Dainty,et al.  Current trends in optics , 1994 .