our distances are not grossly in error.

Taking into account the uncertainties in our photometry ($g\sim0.1$ for stars brighter than $g$=20, increasing to $g\sim0.2$ for fainter sources), the uncertainty on our period determinations, coupled with the uncertainty on the pulsation mode, we estimate the errors on our distances maybe up to 25 percent. If on the other hand the periods we determine are half the true period then we significantly underestimate their distances. Similarly, if the extinction is less than that to the edge of the Galaxy then we also underestimate the distances. Of course, if the period we detect is not due to radial pulsation then the distance is highly uncertain.

(8,6) (-0.8,-0.4)

Our sources have a large spread of distances (Table 1). Assuming the period is due to the fundamental radial pulsation mode then the closest star is 0.6 kpc, while the most distant lies at 32 kpc (the median is 7.0 kpc). Similarly, the sample shows a large spread in height from the Galactic plane, the least distant only 200 pc, with the most distant at 20 kpc. The median height is 1.4 kpc, which equates to twice the scale height of the thick disc of the 