Automatic determination of the large separation. Dark squares indicate the values of EACF tested in 13 frequency ranges between 2 and 220 μHz. Gray values are artifacts cause by the CoRoT low Earth orbit and must be excluded. The horizontal dashed line indicates the threshold level for a detection at the 1% rejection level. The vertical dark gray line indicates the observed signature at Δν ≃ 75 μHz, and the dash-dotted lines the spurious signatures of the daily aliases (11.6 and 23.2 μHz).