Three-dimensional plot of the intensity distribution in a stellar image.

Data were recorded in November 1997 with Hokupa'a mounted on the CFHT f/36 focus (aperture diameter 3.355 m). The object is star SAO 12442 (mag 9.5 in the visible). These 30-second CCD exposures were recorded through a narrow-band filter centered at the wavelength of 0.936 micron. The left image was recorded with the feedback loop turned-off. However, constant voltages were applied to the deformable mirror to remove static aberrations. In addition autoguiding was used to remove any tracking error. The full width at half maximum (FWHM) of this image is 0.6 arc-second and its Strehl ratio is 0.009. The right image was recorded with the feedback loop turned on. The loop update frequency rate was 1.3 kHz. The image FWHM is 0.068" and its Strehl ratio is 0.29. The gain is by a factor of about 9 on the FWHM, and by a factor of about 30 in the Strehl ratio.