Fig 1. USNO 'B' Magnitude Error f(Magnitude)
Red = USNO - Calibrated
Yellow = Best Fit: Y = +3.03 -0.206 * B_cal
Y vertical Tick = 0.1 magnitude
Offset for Magnitude 14.0 'B' = +0.15
Error cancels for Magnitude 14.8

Fig 2. USNO 'R' Magnitude Error f(Magnitude)
Red = USNO - Calibrated
Yellow = Best Fit: Y = +3.33 -0.210 * R_cal
Y vertical Tick = 0.1 magnitude
Offset for Magnitude 14.0 'R' = +0.39
Error cancels for Magnitude 15.9

For any comment, contact Jean-Claude PELLE