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, due to its structural characteristics, the observation direction of an LMT is typically restricted to the zenith. Although off-axis observations can partially extend the observable sky region, they inevitably introduce significant static off-axis aberrations. In addition, various disturbances, such as structure vibration and airflow turbulence, may cause mirror surface fluctuation, which leads 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 traditional wavefront correctors, MFDM can provide both super-large stroke and inter-actuator stroke. In the paper, a convex mirror is first deployed to achieve preliminary compensation of large low-order static off-axis aberrations. Subsequently, an MFDM is designed with respect to the residual aberrations, and an Youla parameterized adaptive control algorithm is developed to realize real-time correction of both static residual and dynamic time-varying aberrations. Finally, an experimental LMT platform is constructed to evaluate the proposed aberration correction system. The experimental results show that the MFDM can achieve a large deformation stroke of over 100μm and reduce the wavefront RMS error of aberration from 53.9μm to 0.18μm. The results demonstrate that the MFDM-combined aberration correction approach provides excellent capability for compensating the extremely large off-axis aberrations, and thus offers an effective solution for expanding the observable sky region of LMTs.