CFHT, Instruments, Imaging, AOB, Instrumentation
The CFHT Adaptive Optics Bonnette :
Preparing your astronomical observations
Although we've done our best designing the AO bonnette,
it will not provide diffraction limited images over the whole
sky. The principles of adaptive correction impose theoretical limits
to what is achievable by an AO system. The correction will get worse as :
If you want to have a quick look on how the performance behaves with
wavelength, guide star magnitude and seeing (excluding the distance to the
guide star), you can follow this link
(in this link, the seeing is quoted in r0. r0 is proportionnal to 1/seeing,
and a seeing of 1 arcsec corresponds to a r0 of 10 centimeters. Typical
free atmosphere seeing is about 0.5 arcsec at CFHT).
- - the seeing gets worse
- - the imaging wavelength gets shorter
- - the magnitude of the guide star increases
- - the distance to the guide star gets larger
If you want to
treat a particular case, or want to have an idea of how the correction
degrades with the distance to the guide star, use the interactive forms
The PSF image will be a 128x128 image, therefore showing a field which
side is 128 times your requested pixel size. This program uses pre-computed
images at selected guide star magnitudes, seeing values
and guide star to object distances to obtain your image.
The attenuation of the modulation transfer function brought
by anisoplanatism effects has been computed separately, assuming a complete
decorrelation between anisoplanatism effects and the other sources of
The pre-computed PSF were obtained by numerical simulation, using a code
developped at CFHT by F.Rigaut. It includes a realistic model of the atmosphere,
close-loop, wavefront sensor and bimorph mirror.
Created 10 November 95.
Page maintained by Jean-Luc Beuzit.
Please send comments to :