In games, aircraft navigation systems and in control systems, users have to track moving targets around a large workspace that may extend beyond the users' viewport. This paper presents on-going work that investigates the effectiveness of two different off-screen visualization techniques for accurately tracking off-screen moving targets. We compare the most common off-screen representation, Halo, with a new fisheye-based visualization technique called EdgeRadar. Our initial results show that users can track off-screen moving objects more accurately with EdgeRadar over Halos. This work presents a preliminary but promising step toward the design of visualization techniques for tracking off-screen moving targets.