Table 1: Magnitudes of the secondary standard stars. The "-'' signs appear where the magnitudes for the stars have not been derived either because they were saturated in some images, which was the case of the B and C stars, or they were faint and therefore gave large photometric errors (>0.08). These were disregarded in the case of the U, B, and near-IR bands of the secondary standards 1-6. The  band magnitudes of A, B, C, and D are taken from Sahu et al. (2000).

Std.	U	B	V	R	I	J	H
1	-	-	19.84 0.02	18.76 0.02	17.48 0.03	-	-	-
2	19.16 0.07	-	18.21 0.01	17.87 0.02	17.48 0.03	-	-	-
3	-	-	19.08 0.02	17.94 0.02	16.57 0.03	-	-	-
4	-	-	18.90 0.02	18.37 0.02	17.86 0.03	-	-	-
5	-	-	20.72 0.04	19.73 0.02	18.68 0.04	-	-	-
6	-	-	19.21 0.01	18.31 0.02	17.34 0.03	-	-	-
A	18.80 0.06	18.80 0.06	17.16 0.01	16.40 0.01	15.64 0.01	14.82 0.02	14.20 0.03	14.04 0.04
B	-	17.91 0.05	16.98 0.01	16.65 0.01	16.29 0.01	15.91 0.02	15.60 0.04	15.57 0.03
C	-	17.69 0.07	16.46 0.01	15.97 0.01	15.50 0.01	14.96 0.02	14.51 0.04	14.42 0.04
D	17.69 0.07	17.33 0.06	15.91 0.01	15.27 0.01	14.65 0.01	13.99 0.02	13.39 0.03	13.28 0.03