Phase Diversity: Experimental Results from the Lick Observatory

In the past, fixed aberrations in large astronomical telescopes were not considered to be a problem as long as the errors were no worse than the seeing at the telescope sight. Adaptive optics are now allowing researchers to correct for local seeing errors as well as fixed aberrations. In order to better understand the correction capabilities it is important to separate the fixed aberration errors from the seeing errors. The Lockheed Palo Alto Research labs ongoing phase diversity program has addressed this problem by using phase diversity techniques to estimate the fixed aberrations in the 1 meter and 3 meter telescopes at the Lick Observatory. The phase information extracted from the focused and defocused images is also used to enhance images of extended objects such as Jupiter, Saturn and the Earth’s moon.