We report the discovery of 1RXS J173006.4+033813, a polar cataclysmic
variable with a period of 120.21 min. The white dwarf primary has a magnetic
field of B = 42+6-5 MG, and the secondary is a M3 dwarf. The system shows
highly symmetric double peaked photometric modulation in the active state as
well as in quiescence. These arise from a combination of cyclotron beaming and
ellipsoidal modulation. The projected orbital velocity of the secondary is K2 =
390+-4 km/s. We place an upper limit of 830+-65 pc on the distance.Comment: ApJ Accepted. 12 Pages, 13 Figures, 6 table
