Contents

Introduction Why the Half Arcsecond Programme was set up. Results Summary Six findings from the programme Publications Major publications by the HAP team HAP People Staff from the ING and elsewhere working on the HAP Intrinsic Seeing quality at the WHT site:  DIMM  measurements All about DIMM Comparison with other observatory sites ESO/Chile comparisons WHT Seeing: 'JOSE' Wavefront sensor  measurements All about JOSE Dome Seeing or None ? WHT Dome Seeing and Comparisons Telescope Focus and Optical Quality Shack-Hartman wavefront sensor measurements Tracking stability All about the WHT tracking system Outer scale of Turbulence Noll's analysis; measurements of the FWHM stellar images