Two-color diagram that combines the K_s magnitude of the 2MASS system and the magnitudes [3.4] and [4.6] of the WISE system, used to identify YSOs. We plot the stars in the 15′ × 15′ area centered on IC 1805, for which the magnitudes K_s, [3.4] and [4.6] have observational errors < 0.06 mag. The two straight lines taken from Koenig et al. (2012) divide the plane into three areas in which YSOs of types I and II and young diskless objects are located.