SBI-1 Limb Darkening

Comparison of wide band solar limb darkening measured (LD) during the SBI1 flight with other indirect estimations:

(2) Integration of a set of monochromatic LD curves from Neckel and Labs (1994), weighted by the spectrum of the solar radiation. This curve agrees well with the SBI derived one, with the exception for ? < 0.2, which corresponds to the last 20 arcsec before reaching the limb. The discrepancy in the last 20 arcsec can not be reasonably explained when considering imperfections in the SBI's optical system. The point spread correction would require a totally unrealistic large amount of scattering or blurring to notably influence the shape of the observed LD.

(3) Total LD function from the Astrophysical Quantities book of Allen 2000, pp. 355-357 (but of unknown origin).

(4) Curve calculated from the gray LD formula (e.g., Foukal 1990, p. 54).