Continuum photometry of solar white-light faculae

We have determined absolute continuum intensities and brightness temperatur es of individual facular grains at a spatial resolution limited by the phi = 50 cm aperture of the SVST on La Palma. A facular region at theta approxi mate to 57 degrees was observed simultaneously in three narrow continuum wi ndows at 450.5, 658.7, and 863.5 nm. We corrected for image degradation by the Earth's atmosphere using the speckle masking method. The brightness tem peratures do not exactly follow the Planck law. The differences of T-blue-T -red = 220 K and T-ir-T-red = -42 K reflect the wavelength dependence of th e continuum formation depth. The (red) temperatures of 250 facular grains s how excesses between 250 and 450 K above their undisturbed neighborhood. Th e wavelength dependence of the relative intensity ratios C-lambda = [I-fac/ I-phot](lambda) show a large scatter around mean values of C-blue/C-red = 1 .075 and C-ir/C-red = 0.98. We determined the center-to-limb variation of t he 863.5 nm continuum contrast for 0.17 < cos theta < 0.39 by measuring 270 grains in reconstructed facular images. The upper envelope of the data poi nts increases linearly to 1.5 at cos theta = 0.17. Application of the mean color dependence yields green contrasts up to C-550 = 1.7, which is far hig her than previously observed values. The behaviour for cos theta < 0.17 is estimated from (unreconstructed) frame-selected best images taken over a ti me interval of 7 hours. Six distinct facular regions clearly discernible du ring the whole time interval indicate a slight contrast decrease towards th e extreme limb. The observed quantities are useful for an adjustment of mod el calculations and for a discrimination of competing models.