Simulation of a spotted stellar surface in Mollweide projection and seen almost pole on as Vega. Deep blue are dark spots which appear in emission in the dynamical spectrum. Phase 0 is at the left of the stellar map (rotation vector points towards the top). Stellar rotation is counterclockwise in this representation. A spot at the central meridian of the stellar sphere (in front of the observer) would have phase zero and appear on the left of the map. Phases increase clockwise on the stellar sphere. If we read the map in analogy to the terrestrial coordinates, then the phase would correspond to the negative longitude. Left: original map of the stellar surface. Middle: dynamical spectrum. Right: reconstructed stellar surface map. Top: single spot. Middle: complex pattern of three spots of different sizes. Bottom: simulation of a realistic dynamical spectrum (signatures with an amplitude of 1.5 × 10⁻⁴ F/F_c and a noise of σ = 5 × 10⁵−5).