Although adaptive optics (AO) systems have been developed to compensate for atmospheric turbulence, their application is mostly limited to large size (1.5 to 8 m) telescopes due to high cost and complexity. In particular, for small to medium aperture telescopes for which the need for AO correction is critical, AO systems have different requirements such as compactness and transportability. We report on the realization and the on-sky test of an extremely small adaptive optics module (XSAO) based on a multiactuator adaptive lens. Observations were performed on an 11-in. commercial telescope and a 1-m scientific telescope with minimal modifications. The results show a strong improvement of the acquired images for different types of observed objects, such as bright stars, double stars, planets, and deep sky objects.