This is one of the richest field of the entire sky. All kinds of nebulae (dark, emission and reflection) are visible in the area. From left to right are the following: IC431 and IC432 (two reflection nebulae), NGC2024 (the Flame Nebula, an emission nebulosity near Alnitak, Zeta Orionis), NGC2023 and IC435 (two other reflection nebulae) and B33 (the Horsehead Nebula), one of the best examples of dark nebulae. The large area of emission nebulosity on which is clearly spotted B33 is IC434.