The visibility function and its effect on the observed characteristics of sunspot groups

A three-dimensional 3D model of the Minnaert diagram was constructed by expansion in time. It is proved that the Minnaert classical diagram and the diagram of observational conditions of sunspot groups can be generated by projecting the 3D model of the Minnaert diagram into two fundamental planes whereas the projection into the third plane creates a new diagram referred to as the diagram of boundaries of observable sunspot group areas. The 3D model of the Minnaert diagram was also used to establish the relation between the Minnaert modified diagram and a modified diagram of observational conditions of sunspot groups if observations are made once every 24 hours. (author). 9 figs., 1 tab., 11 refs