Interstellar extinction A_V as a function of distance in the IC 1805 area of a diameter of 15′ for stars in the A0–A5 (blue crosses) and A6–F0 (red dots) groups, considering that all of them belong to luminosity class V. The stars within rectangles a) and b) can be luminosity III or IV stars, see the text for discussion. The stars within rectangle c) can be late-type giants. The limiting magnitude curves for A3 V stars of r = 19 mag and for A8 V stars of r = 13 mag are shown. The arrow close to the x-axis shows the shift when a luminosity III star is considered to be of luminosity V. The absolute errors of distances at d = 2 kpc, shown in the error cross, are due to the acceptance of the mean values of absolute magnitudes for the groups A0–A5 and A6–F0.