Automating the Synthetic Field Method:Application to Sextans A
  We have automated the ``Synthetic Field Method'' developed by Gonzalez et al.(1998) and used it to measure the opacity of the ISM in the Local Group dwarf galaxy Sextans A by using the changes in counts of background galaxies seen through the foreground system. The Sextans A results are consistent with the observational relation found by Cuillandre et al. (2001) between dust opacity and HI column density in the outer parts of M31. 
Benne W. Holwerda (1 and 2), Ronald J. Allen (1) and Pieter C. van der   Kruit (2) ((1) Space Telescope Science Institute, (...