Authors: G.A. Chapman, A.M. Cookson, S.R. Walton
Affiliation: California State University, Northridge, San Fernando Observatory
The largest changes in Total Solar Irradiance (TSI) are associated with the
passage of large sunspots across the solar disk. Photometric measurements of
sunspot deficits from ground-based images are important for understanding the
details of how sunspots and other forms of solar activity affect the TSI. Photometric
solar images have been obtained at the San Fernando Observatory (SFO) since
mid-1985 with the Cartesian Full Disk Telescope (CFDT1) and since mid-1992 with
CFDT2. Sunspot deficits are calculated from red images obtained at a wavelength
of 632 nm. More recently, a new source of ground-based photometric images has
become available from the Precision Solar Photometric Telescope (PSPT). Sunspot
deficits calculated from both the SFO/CFDT2 and the Mauna Loa/HAO PSPT are being
compared. The correlation between the two data sets is quite high. Having data
from two locations reduces the amount of missing days. Progress toward creating
a composite record of sunspot deficits will be described.
This work has been partially supported by grants from NASA and the NSF.