We present multi-epoch , total intensity , high-resolution images of 43GHz , v=1 , J=1-0 SiO maser emission toward the Mira variable R Cas .
In total we have 23 epochs of data for R Cas at approximate monthly intervals over an optical pulsation phase range of \phi = 0.158 to \phi = 1.78 .
These maps show a ring-like distribution of the maser features in a shell , which is assumed to be centred on the star at a radius of 1.6 \to 2.3 times the radius of star , R _ { \star } .
It is clear from these images that the maser emission is significantly extended around the star .
At some epochs a faint outer arc can be seen at 2.2 R _ { \star } .
The intensity of the emission waxes and wanes during the stellar phase .
Some maser features are seen infalling as well as outflowing .
We have made initial comparisons of our data with models by Gray et .
al .
( 11 ) .