  Occulting galaxy pairs have been used to determine the transmission and dust
composition within the foreground galaxy. Observations of the nearly face-on
ring-like debris disk around the solar-like star HD 107146 by HST/ACS in 2004
and HST/STIS in 2011 reveal that the debris ring is occulting an extended
background galaxy over the subsequent decades. Our aim is to use 2004 HST
observations of this system to model the galaxy and apply this to the 2011
observation in order to measure the transmission of the galaxy through the
outer regions of the debris disk. We model the galaxy with an exponential disk
and a S\'{e}rsic pseudo-bulge in the V- and I-band, but irregularities due to
small scale structure from star forming regions limits accurate determination
of the foreground dust distribution. We show that debris ring transit
photometry is feasible for optical depth increases of $\Delta \tau \geq$ 0.04
($1 \sigma$) on tens of au scales the width of the background galaxy { when the
2011 STIS data are compared directly with new HST/STIS observations, instead of
the use of a smoothed model as a reference.
