Context :

Aims : We report on the discovery of J0644+3344 , a bright deeply eclipsing cataclysmic variable ( CV ) binary .

Methods : Optical photometric and spectroscopic observations were obtained to determine the nature and characteristics of this CV .

Results : Spectral signatures of both binary components and an accretion disk can be seen at optical wavelengths .
The optical spectrum shows broad H I , He I , and He II accretion disk emission lines with deep narrow absorption components from H I , He I , Mg II and Ca II .
The absorption lines are seen throughout the orbital period , disappearing only during primary eclipse .
These absorption lines are either the the result of an optically-thick inner accretion disk or from the photosphere of the primary star .
Radial velocity measurements show that the H I , He I , and Mg II absorption lines phase with the the primary star , while weak absorption features in the continuum , between H \alpha and H \beta , phase with the secondary star .
Radial velocity solutions give a 150 \pm 4 km s ^ { -1 } semi-amplitude for the primary star and 192.8 \pm 5.6 km s ^ { -1 } for the secondary , resulting in a primary to secondary mass ratio of q =1.285 .
The individual stellar masses are 0.63 - 0.69 M _ { \odot } for the primary and 0.49 - 0.54 M _ { \odot } for the secondary , with the uncertainty largely due to the inclination .

Conclusions : The bright eclipsing nature of this binary has helped provide masses for both components with an accuracy rarely achieved for cataclysmic variables .
This binary most closely resembles a nova-like UX UMa or SW Sex type of cataclysmic variable .
J0644+3344 , however , has a longer orbital period than most UX UMa or SW Sex stars .
Assuming an evolution toward shorter orbital periods , J0644+3344 is therefore likely to be a young interacting binary .
The secondary star is consistent with the size and spectral type of a K8 star , but has the mass of a M0 .