Abstract
We investigate the possibility of performing precision astrometry on saturated stellar images of the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2). We obtain the position of the stellar photocentres by using a centring technique which utilises the diffraction pattern produced by the secondary mirror support. This technique appears to be very promising in the astrometrical analysis. It allows a precision of the order of 10 milliarcseconds in WFPC2 images.
