to assess whether the period we detect is either the fundamental or first over-tone period (or whether the period is even due to a radial mode). Some help is found from the fact that the period of the first over-tone is less than the period of the fundamental period by a factor of 0.775 (Poretti et al 2005). We determined the distance to each source assuming the period we detect was the fundamental radial mode and also by assuming the period was the first over-tone (we show the distance and corresponding height from the Galactic plane to each source in Table \[candidates\] under both assumptions). The error on the distance assuming we do not know the pulsation mode of the star is $\sim$17 percent.

As a zeroth order test, we show in Figure \[dist-vo\] the relationship between the dereddened $V$ mag (assuming the extinction to the edge of the Galaxy as determined above) and the derived distance assuming the period is the fundamental mode and also the first over-tone. Whilst one can argue that any individual object may give a better overall linear relationship if one assumes the period is one or the other mode, it gives us confidence that 