Cross correlation functions measured for an artificial single star of 1 arcsec apparent diameter (100 μm aperture at 23 m), normalized to zero baseline, show how (a) the temporal coherence gradually decreases with increasing time delay; and (b) the spatial coherence gradually decreases with increasing baseline. In this particular case, the normalized value for zero baseline was taken as the autocorrelation for delays in the range 1−10 μs (at much shorter delay times the autocorrelation rises to unphysical values due to detector afterpulsing). These effects were avoided in other measurements where the zero baseline was realized by cross correlating two telescopes behind one beamsplitter.