The Solar Optical Telescope (SOT) onboard Hinode is a diffraction-limited optical telescope designed to observe the solar photosphere and chromosphere with high spatial and temporal resolution. SOT operates primarily in visible and near-ultraviolet wavelengths, providing continuous, seeing-free observations of solar fine structure at spatial scales down to approximately 0.2–0.3 arcseconds.

The instrument consists of a 50-cm aperture Gregorian telescope feeding multiple focal-plane instruments, including a Broadband Filter Imager (BFI), a Narrowband Filter Imager (NFI), and a Spectro-Polarimeter (SP). These subsystems enable high-resolution imaging, Doppler measurements, and precise vector magnetic field diagnostics through spectro-polarimetric observations.

SOT is optimized to investigate the structure and evolution of solar magnetic fields, including sunspots, active regions, and small-scale magnetic elements, as well as their role in driving dynamic phenomena such as flares and coronal heating. Its spectro-polarimetric capability provides measurements of the full vector magnetic field in the photosphere, enabling detailed studies of magnetic energy buildup and release.

SOT observations are routinely combined with data from the X-Ray Telescope (XRT) and the EUV Imaging Spectrometer (EIS) to provide a comprehensive, multi-layer view of the solar atmosphere from the photosphere to the corona.