The SPUV Sun Photometer measures direct normal solar irradiance at up to ten narrowband wavelengths from 300 in the UV-B through  1020 nm in the near-IR, and is the world's most advanced commercial solar sun photometer. Thermally stabilized, environmentally sealed state-of-the-art interference filters, with energy-absorbing visible pre-filters on UV channels provide long term calibration stability. Instead of using a rotating filter wheel, it makes measurements simultaneously across all channels meeting the Baseline Solar Radiation Network's requirements for atmospheric turbidity measurements. A modular mechanical design permits rapid channel service. The SPUV  mounts on most solar trackers (shown here mounted on the ST-1). The SPUV system includes the YESDAS-2 datalogger and works with YESDAS Manager data analysis software.