Distant supernovae probe the history of cosmic expansion and star formation, and provide important information on their progenitor models. Investigation of supernovae type Ia for  are needed to reveal any evolution in their intrinsic properties, and thus their utility as existing distance indicators.  One approach to extend the redshift range beyond the reach of our telescopes is to use galaxy clusters as gravitational telescopes. Conversely, lensed supernovae can be used as probes for testing cluster lens model predictions. In this licentiate thesis, I present a 5-year ground based near-infrared search for gravitationally magnified supernovae behind the galaxy cluster A1689. Abell 1689, at z=0.187, is a one of the best-studied clusters with an extended Einstein radius, making it particularly suited as a gravitational telescope. Our search resulted in the discovery of one highly magnified supernova type II at z=1.703 and two transient objects (probably type IIP and Ia, in host galaxies at redshifts  and ), which is  in agreement with the survey expectations.