Table 1: B, V, R, I magnitudes of the reference stars used in our analysis.

Star	B	V	R	I
A, 2	12.03	11.51	11.20	10.92
B, 3	13.06	12.48	12.10	11.79
C, 5	14.17	13.58	13.20	12.85
D, 6	14.25	13.66	13.28	12.97