FWHM of the dust tail of comet E3 vs. distance from the nucleus in the observation image taken on 10 October 2022 when Earth was located almost in the orbital plane of comet E3. The horizontal error bars show the distance range along the tail that was used to measure the FWHM, and the vertical bars indicate the range of uncertainties of the FWHM profiles. The red and blue lines denote the best-fitting relation θ_⊥ ∝ l^1/2 between the FWHM of the tail and the distance from the nucleus.