ESO Faint Object Spectrograph and Camera
EFOSC2/CCD#40 PSF Distortion

EFOSC2, being a Focal Reducer, distorts the PSF to a considerable extent and this distortion varies across the CCD. We determined the PSF shape variation by determining the PSF ellipticities in acquisition (20 second exposure) images of dense stellar fields under good seeing (< 0.75 arcsec) conditions and then averaged the values as a function of position on the CCD. The resulting PSF map is plotted below.

The vectors indicate the orientation and magnitude of the PSF ellipse at that location.

It must be noted that this represents the minimum distortion that one should expect, which is "intrinsic" to the instrument/CCD combination. The image quality on any single image could be worse due to improper focus, telescope tracking effects, telescope optics distortion (due to stresses in primary and secondary mirrors etc).

Send comments to : ls-spectro

Last modified: Tue Jan 15 20:23:48 CLST 2002

[3.60 & CAT Homepage][La Silla][ESO][Observing][Search][Help][News]