Fig. 3

Schematic view of \(\overrightarrow {{L_{\text{V}} }}\) in an instrument coordinate. Schematic view of \(\overrightarrow {{L_{\text{V}} }}\), Venus and a Venus image in the instrument coordinate (from Fig. 1 of Ogohara et al. 2012). \(\overrightarrow {{L_{\text{V}} }}\) is a unit vector from the focal point, O, to the center of Venus, C. The center of the elliptical Venusian limb is D. The line of the major axis is assumed to pass through Q which is the point of intersection of the CCD plane and the line of sight. H is the point of intersection of the CCD plane and the line from C to O