The microarcsecond quasar J1819+3845
  We present new WSRT observations of the micro-arcsecond quasar J1819+3845. All short term variations are attributed to interstellar scintillation of a source which is at most 30 micro-arcseconds in diameter. The timescale of the modulations changes over the year, which we interpret as due to a peculiar velocity of the scattering medium. The scintillation behaviour can be used to determine sub-structure in the source. 
J. Dennett-Thorpe, A. G. de Bruyn