We present time-series spectroscopy of two short period cataclysmic variables , CC Scl and V2051 Oph , to test the efficiency of Doppler tomography-based methods in constraining orbital parameters of evolved cataclysmic variables .
We find that the Ca II triplet lines offer superior diagnostics , revealing emission components from the mass donors and sharp images of the accretion discs .
Furthermore , we use Monte-Carlo methods to estimate the uncertainties from ensembles of Doppler maps .
We compare our new methods against traditional radial velocity methods and show that they offer a valid route towards system parameter determination .
Our analysis of CC Scl suggests a low mass ratio of q = 0.08 \pm 0.03 with a primary velocity of K _ { 1 } = 37 \pm 14 km/s .
This mass ratio is in between the pre- and post-period minimum status , however our K _ { 1 } solution favours a post-period minimum system .
Our derived parameters for V2051 Oph ( q = 0.16 \pm 0.03 , K _ { 1 } = 97 \pm 10 km/s ) are in agreement with the eclipse solution ( q = 0.19 \pm 0.03 ) , offering a direct validation of our methods .