J vs. J − K diagram of the stars in the central region of G342.07+00.42. Their magnitudes are from the 2MASS and VISTA catalogues; we do not use VISTA data for stars brighter than 12.5 mag in J and K and 13.0 mag in H as they are probably saturated. The main sequence for OV stars is from Martins & Plez (2006), for visual extinctions of 0 mag, 20 mag, and 40 mag, and assuming a distance of 4.7 kpc; the extinction law is that of Rieke & Lebofsky (1985). The 2MASSphotometry of highly reddened stars must be regarded with caution as shown by the discrepancy between the 2MASS and VISTA measurements of some stars (joined by black lines). The stars are identified by their numbers according toFig. F.2.