Wide-field performance gradient at a mid-latitude site and at Dome C

Dome C is considered a site particularly suited for wide-field imaging thanks to its shallow surface turbulent layer and its weak turbulence in the free atmosphere. What is the quantitative gain one can hope to achieve at Dome C with respect to a mid-latitude site? With the point spread function model defined analytically in the spatial frequency domain we are better able to connect the morphological and statistical behaviour of the turbulence profile to the trade-off between the adaptive telescope's field of view and a figure of merit for survey rate. A familiar image quality figure of merit is the radius of 50% encircled energy, and for J-band images it quickly identifies the requirement that will make a Dome C telescope, 8 meters above the ice, competitive with a mid-latitude one. From the radius of 50% encircled energy we derive the wide-field survey rate equation to estimate the impact of uncertainty in the vertical distribution of ground-layer turbulence on the trade-off between field of view (in the domain 10-20 arcminutes) and their survey rate.