decided to restrict our search for blue pulsating variables in the range of 40 min to 2 hrs.

Observations
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(14,6.5) (-0.8,-0.5)

The RATS observing strategy is to take a series of 30 sec exposures of a given field using the wide-field cameras on the Isaac Newton Telescope in La Palma and the MPG/ESO 2.2m on La Silla for a duration of $\sim$2 hrs. To date our survey has discovered around 1.2$\times10^{5}$ variable stars (see Barclay et al 2011 for a full description of our reduction process). Based on their photometric properties, a small sub-sample has been selected for followup spectroscopic observations to determine their nature.

To narrow our search for blue pulsators in our RATS data, we restricted our search to a range in both magnitude and colour. The intrinsic colour of SX Phe stars is typically $(B-V)_{o}\sim$0.1 to 0.35 (eg Poretti et al 2008), which corresponds to $(g-r)_{o}=$–0.12 to 0.14. This is virtually identical to the colours for $\delta$ Sct stars (eg Rodríguez et al 2000). Many of our fields lie at low Galactic latitude and hence have high extinction. To reduce the contamination with other types of sources at low Galactic latitudes we allow a maximum extinction 