Asteroid: 1999 JB

Predicted positions for POSS plate A0ZA with length of trail in arcsecs. The predictor generates ephemerides for start, midth, and end of trail, along with the predicted magnitude. 

     J99J00B   1992 05 01.16806 11 20 21.68 +21 21 28.4          20.1        675
     J99J00B   1992 05 01.18542 11 20 20.96 +21 21 34.6          20.1        675
     J99J00B   1992 05 01.20278 11 20 20.23 +21 21 40.8          20.1        675
                      -20.20"         12.3"        23.7"

Actually measured positions, start and end of trail 

Observations:
     J99J00B  P1992 05 01.16806 11 20 22.28 +21 21 29.9 A0ZA                 675
     J99J00B  P1992 05 01.20278 11 20 20.84 +21 21 40.7 A0ZA                 675
Link to the MPEC which published the improved orbit.

DSS image of 1999 JB from May 1, 1992 on POSS plate A0ZA