Figure S2. Planetarium Starry Skies from How animals follow the stars

Figure S2. Planetarium Starry Skies (a.) (i.) Schematic of an optomechanical “dumbbell” starball projector. Stars for each hemisphere are projected from two separate balls via lenses (shown as bright patches). Two cylinders near the pivot project the Milky Way streak. (ii.) Sky conditions used by Dacke and colleagues (2013; Fig. 1) projected from a MkIII starball projector (Zeiss AG, Germany; 1930) in Wits Planetarium (Johannesburg, South Africa), as in the original study. (iii.) The same conditions displayed on a 6 m dome by a newer optomechanical projector (Skymaster ZPK 2: Zeiss AG, Germany; 1979) at the planetarium in which Sauer (1956) performed the first study of avian stellar orientation (Olbers Planetarium: Bremen, Germany). (b.) (i.) A “Digital” projector. By using a fisheye lens, a single projector can illuminate the entire dome. (ii.) Conditions similar to (a) were projected onto a 6 m dome by a “digital” projector (Definiti: Sky-Skan Inc., Nashua, USA; 2010; Vattenhallen Science Centre: Lund, Sweden). The content projected by this system is more versatile than the starball, but effective contrast between dark and bright sky regions is somewhat limited. (c.) (i.) A Hybrid system. A combination of optomechanical and single-aperture projectors can exploit the high-contrast stars and versatile skylight produced by each. (ii.) Similar conditions projected onto an 8 m dome by a hybrid starball and multi-projector system (Skymaster ZPK 4: Zeiss AG; 2013; and 5 Definiti projectors: Sky-Skan Inc.; Museum am Schölerberg: Osnabrück, Germany). N.B. All images normalised to a maximum value of 3×10^6 photons cm^-2 s^-1 sr^-1 nm^-1 as in Fig. 2.