Summary
We present low-resolution turbulence pro les of the atmosphere above Dome C, Antarctica, measured with the MASS instrument during 25 nights in March { May 2004. Except for the lowest layer, Dome C has signi cantly less turbulence than Cerro Tololo and Cerro Pachon. In particular, the integrated turbulence at 16 km is always less than the median values at the two Chilean sites. From these pro les we evaluate the photometric noise produced by scintillation, and the atmospheric contribution to the error budget in narrow-angle di erential astrometry. In comparison with the two mid-latitude sites in Chile, Dome C o ers a potential gain of about 3:6 in both photometric precision (for long integrations) and narrow-angle astrometry precision. These gain estimates are preliminary, being computed with average wind-speed pro les, but the validity of our approach is con rmed by independent data. Although the data from Dome C cover a fairly limited time frame, they lend strong support to expectations that Dome C will offer signi cant advantages for photometric and astrometric studies.