The ASTRI-Horn telescope has been developed under the leadership of the Italian National
Institute for Astrophysics (INAF) as a prototype of a compact aplanatic dual-mirror (4 m diameter) Imaging Atmospheric Cherenkov Telescope (IACT) with a large FoV (8◦). It is the pathfinder of the small-size telescopes adopted for both the ASTRI Mini-Array (Tenerife, Canary Islands) and the SST/CTA array (Paranal, Chile) to perform 1-200 TeV gamma-ray astronomy with an unprecedented combination of high angular/energy resolution and flux sensitivity across a large Field of View. ASTRI-Horn is a complete end-to-end system; since 2014 it is installed in Italy at the INAF "M.G. Fracastoro" observing station (Mt. Etna, Sicily). The telescope already successfully demonstrated, first time ever, the optical behavior of a dual-mirror Schwarzschild-Couder telescope as a Cherenkov system, and also obtained the first gamma-ray source detection, the Crab Nebula. During 2020-2022, ASTRI-Horn - which operates in a harsh environment on an active volcano - has been subject to significant maintenance and refurbishment to restore systems and improve performance. Mirrors have been substituted, adopting high-performance new-recipe coatings, and the camera electronics has been further optimized. Now the telescope is extensively used for cosmic rays, gamma rays, and muon-radiography of the Etna volcano investigations.