USNO Magnitudes versus calibrated

Field RA = 18h19.4m DC = -25°23'

Fig 1. USNO 'B' Magnitude Error f(Magnitude)
Red = USNO - Calibrated
Yellow = Best Fit: Y = +5.57 -0.236 * B_cal
Y vertical Tick = 0.1 magnitude
Offset for Magnitude 14.0 'B' = +2.27
Error cancels for Magnitude 23.7

Fig 2. USNO 'R' Magnitude Error f(Magnitude)
Red = USNO - Calibrated
Yellow = Best Fit: Y = +4.77 -0.226 * R_cal
Y vertical Tick = 0.1 magnitude
Offset for Magnitude 14.0 'R' = +1.61
Error cancels for Magnitude 21.1

For any comment, contact Jean-Claude PELLE