Variation of parameter B of the scaling function for uncertainty in RV (S_RV) with log g and metallicity for order-sorting filters, HR10, HR15N and HR21. a) Shows the value of B determined for data in three equal bins of log g. Numbers indicate the sample size. b) Shows the value of B determined for data in three equal bins of [Fe/H]. For filter HR15N only the values shown in the upper two bins are reliable due to the low number of targets with [ Fe/H ] < − 1.