Observation scheme. The measurements were performed at ten heliocentric positions (μ = cos θ) from the disk center (DC, μ = 1.0) toward the solar limb (μ = 0.3) along four radial directions: northern (blue, circle), southern (green, rectangle), eastern (orange, diamond), western (red, triangle) axis. The positions are drawn as black ellipses indicating the spatially covered area.