As reported in the previous NOAO Newsletter (December 1998) and in Solar News (February 15, 1999 issue), the NSO solar adaptive optics program at NSO/Sac Peak has achieved a major milestone by closing the servo loop with solar granulation and small pores as the wavefront sensing target at the R.B. Dunn Solar Telescope (DST) in early November 1998. This is the first time adaptive optics has been shown to work with solar granulation as the wavefront sensing target. First images and movies from the November 1998 engineering run and a brief description of the solar AO system, which is based on a 24 subaperture correlating Shack-Hartmann wavefront sensor, are now available on the internet (www.sunspot.noao.edu/AOWEB).
The accompanying figure shows simultaneous corrected and un-corrected images of granulation taken at 500 nm. The images were recorded using two synchronized video cameras and a split-screen electronics. The image scale and the field-of-view for the two images are slightly different (axes are labeled in arcsec). The images were digitized from videotape using a frame grabber. Despite the poor reproduction of the video images, it is obvious that the image correction performed by the AO system is substantial. The correction is slightly better in the center of the field of view, giving an indication of the size of the isoplanatic patch. However, a substantial improvement in image quality can be seen over the entire FOV. This indicates that a substantial amount of local turbulence close to the telescope and possibly aberrations in the telescope optics were present during these observations. A detailed performance evaluation of the solar AO system was conducted during a second engineering run in mid-February 1999, during which an attempt was made to collect the first science data.
T. Rimmele, R. Radick, R. Dunn, K. Richards