Fig 1. USNO 'B' Magnitude Error f(Magnitude)
Red = USNO - Calibrated
Yellow = Best Fit: Y = +0.76 -0.074 * B_cal
Y vertical Tick = 0.1 magnitude
Offset for Magnitude 14.0 'B' = -0.28
Error cancels for Magnitude 10.2

Fig 2. USNO 'R' Magnitude Error f(Magnitude)
Red = USNO - Calibrated
Yellow = Best Fit: Y = +0.18 -0.023 * R_cal
Y vertical Tick = 0.1 magnitude
Offset for Magnitude 14.0 'R' = -0.14
Error cancels for Magnitude 7.8

For any comment, contact Jean-Claude PELLE