Solar Sunspot Photometry

San Fernando Observatory (SFO) Photometric Observations (Data Documentation) 1985-1998

Rapid changes in the total solar irradiance from space borne sensors are largely due to the passage of large sunspots across the disk. The effects of sunspots have often been modeled using ground-based observations by the use of a Photometric Sunspot Index (PSI), usually assuming all sunspots have the same thermal structure. The SFO data measure the mean temperature or bolometric contrast and corrected hemispherical areas, incorporating these into the PSI calculation. The PSI is calculated for each sunspot group and then summed over all groups present on the solar disk. Recent data