When a celestial rotating body is observed with a high spectroscopic resolution instrument (like GOLF), were this resolution is smaller than the solar linewidth, it is possible to find sensitivity differences over the whole disk (Brookes et al. 1978b). In fact, this can be calculated by instantaneously taking the images of and by appropriate integration of Eq. (1 (click here)) at any epoch of the year. Figure 3 (click here), shows the result obtained for the sensitivity variation across the solar disk. In the nearest symetrical case, around end September where V is only 100 ms-1, there is a factor of 4.05 for the red component and 3.85 for the blue one between the maximum and the minimum contributions in the solar disk. In the less symetrical case, around April where ms-1, the factors are 3.96 and 3.73.
Figure 3: Maps of the relative contributions of each point over the solar disk to the scattered intensities at each wing of the sodium doublet,
and (left and right respectively) as
they are measured by the GOLF instrument. We have considered only the Zeeman
components without the magnetic modulation
Comparing the sensitivity differences between the two wings we find that it is less than a and during the year it changes . Moreover, in April, the reduction of the sensitivity due to the change of the working points is less than a . In conclusion, the selected working points show small differences in their sensibility during the year and between the two wings.