Gaussian vs. JK errors for the κg NVSS cross-spectrum estimated in bins Δ_ℓ = 30 in the range 11 ≤ ℓ ≤ 310. Upper panel: Gaussian errors for different b(z)+N(z) model combinations, specified in the labels, shown as colored dots and dashed curves. Black dots and dashed curve indicate JK errors. Errors have been estimated from the diagonal elements of the Gaussian covariance (Eq. 18) and JK covariance (Eq. B.1). Bottom panel: Per cent difference between the Gaussian and JK errors.