PSFs obtained with Hokupa'a

Hokupa'a gives spectacular performance in I,J,H & K bands

1. These narrow I band (0.936 microns) images show the spectacular performance of Hokupa'a ("immovable star" in Hawaiian) our new 36 actuator AO system on the 3.6m CFHT telescope. The first image was taken with the AO system set to remove static telescope aberrations the second image was taken with the AO loop turned on. Each image is a 30 second integration on the sky. The guide star (SAO12442) is relatively bright at mv=9.5. The Strehl (peak brightness) improvement between the images is a factor of 30.5 (at D/ro=9.6). The field of view on these CCD images is 1.17 arc seconds. The plate scale for the images is 0.0145 arc seconds per pixel, making the open loop FWHM 0.6" (diameter of the green circle) and the closed loop FWHM 0.067". The diffraction limit for the telescope in I band is 0.059". The slight broadening of the image from the diffraction limit is due to residual tip-tilt motion and small aberrations in the CCD camera relay lens, this means that there is significantly more light in the central peak, than would be indicated by the image Strehl ratio. We estimate the "ON" image Strehl ratio to be 0.29 We also find 27% of the total flux can be found within 0.065" of the star (contained in the slightly broadened diffraction peak). NB: the "OFF" image is scaled to the same peak value as the ON image, and the stretch is logarithmic.

Image with loop turned off I BAND CORRECTION
Image with loop turned on a linear surface map of the PSF (click for a clearer image)

2. The same PSF star through narrow band J, H and K filters:
Image with loop turned on more visible and infrared PSFs

3. Deep images showing how well Hokupa'a can detect faint companion stars:
I Band Image of faint companion I Band image of faint companion detection
I,J,H,K Images of faint companion I,J,H,K Faint companion detection images

Laird Close, Institute for Astronomy, University of Hawaii
close@galileo.ifa.hawaii.edu
Last modified: March 3, 1998