The liquid mirror telescope (LMT) features low cost, high surface optical quality, and ease of fabrication, providing an economical and efficient alternative to conventional solid-mirror telescopes. However, owing to its structural characteristics, the observation direction of an LMT is typically restricted to the zenith. Although off-axis observations can partially expand the observable sky region, they inevitably introduce significant static off-axis aberrations. In addition, various disturbances, such as structural vibration and atmospheric turbulence, may cause mirror surface fluctuations, which lead to dynamic aberrations. To correct these aberrations and thereby expand the observable sky region of the LMT, this paper proposes an aberration correction system based on a magnetic fluid deformable mirror (MFDM). Compared with the traditional wavefront correctors, MFDM can provide both a large stroke and a large inter-actuator stroke. Specifically in this paper, a convex mirror is first employed to provide preliminary compensation of large low-order static off-axis aberrations. Subsequently, an MFDM is designed with respect to the residual aberrations, and a Youla-parameterized adaptive control algorithm is developed to achieve real-time correction of both residual static aberrations and dynamic time-varying aberrations. Finally, an experimental LMT platform is established to validate the proposed aberration correction system. The experimental results show that the MFDM can achieve a deformation stroke exceeding 100 μm and reduce the wavefront RMS error from 53.9 to 0.18 μm. The results further demonstrate that the MFDM-combined aberration correction approach exhibits excellent capability in compensating the exceptionally large off-axis aberrations, and thus offers an effective solution for expanding the observable sky region of LMTs.