Why Adaptive Optics?

In astronomy, the effects of atmospheric blurring can be avoided by going into space. However, facilities like the Hubble Space Telescope are extremely costly to build and operate, and despite their expense, space-based telescopes remain relatively small. To compare HST and the Keck Telescopes, HST cost roughly 20 (?) times more to build and launch, yet Keck has 20 times the light gathering area and -- potentially -- 4-5 times better resolution.

One technique that has been developed for overcoming atmospheric blurring is speckle interferometry, in which hundreds of very short exposures ("specklegrams") are later analyzed to reconstruct the unblurred image. However, because the specklegrams must be short exposures and at the same time have good signal-to-noise, speckle interferometry is limited to imaging very bright objects. Furthermore, results can only be seen following a lengthy reconstruction process.

Adaptive optics compensates for atmospheric turbulence while the observations are in progress. In principle, very faint objects can be imaged in long exposures, provided there is a bright "reference beacon" nearby to allow the AO system to analyze the atmospheric effects. Furthermore, AO's real-time nature means that spectroscopy becomes possible on very small angular scales, and it follows that fainter objects can be studied because less of the night-sky background needs to be included in the light being analyzed.

Vision science does not have any means of avoiding the imperfections in the cornea and lens in living subjects, so AO is the only option for studying living retinal tissue. Furthermore, a full adaptive optics system can compensate for micro-fluctuations in eye muscles, which means that the eye does not have to be temporarily paralyzed while under examination.

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