RZ, May 30 2012
The figure fwhm_planet.png gives effective FWHM ~16 and 20arcsec for an 8arcsec disk convolved with 10 and 17arcsec Gaussians (input FWHM) correspondingly. This cannot be correct ! The upper limits for the resulting FWHM can be calculated for a convolution of a Gaussian with FWHM=8arcsec instead a disk: sqrt(82+102)=12.8 and sqrt(82+172)=18.8arcsec. To get the correct numbers I calculated the 2 cases, i.e. convolved an 8arcsec disc with FWHM=10 and 17arcsec Gaussians. The resulting sources are very well represented by Gaussians with FWHM of 11.1 and 17.7arcsec (no restrictions for the fitting). The difference of the resulting sources and the Gaussian fits are presented below. The discrepancy is -0.4 to +0.14% for the convolution with a FWHM=10arcsec and much below 1% for the convolution with a FWHM=17arcsec Gaussian. The effective FWHM in figure fwhm_planet.png therefore do not represent the correct values - or do I have a problem in reading this figure ?