Published online by Cambridge University Press: 26 May 2016
Microlensing surveys have ruled out that the dark halos of the Milky Way and M31 are composed entirely of massive compact halo objects (MACHOs) for a wide range of MACHO masses. We have tried using the Subaru telescope to improve the limit on Moon-mass MACHOs, which is the lowest decade in MACHO mass that can be probed by microlensing. Unfortunately, only a half-night of Subaru data was obtained and this is not enough; at least 2 nights of data are required. the current limit is based on nearly 6 years of observations with smaller telescopes.