Top, taken by Michael Grossmann at Kämpfelbach, Germany on 15 May 2011, and a
tertiary-quaternary rainbow pair (bottom, taken by Michael Theusner near Schiffdorf,
Germany on 11 June 2011). See Theusner, pp. F129-F133,
and Grossman et al., pp. F134-F141 for details. Three papers in this issue describe these observations and analyze the
visibility of the extraordinarily rare tertiary rainbow.