Correlation between pixels in the Lyα-forest and pixels in the CIV-forest, ξ^pl(λ₂−λ₁,θ) for small wavelength differences. The wavelength difference and angular separation have been transformed to pseudo-separations assuming Lyα absorption in both forests. The red points show the correlation for pairs on the same halfplate . The much smaller correlations for different half-plates are the blue points. The red line represents the prediction for our model of calibration and sky noise.