Really excellent work and excellent images, thanks for posting. Clouded out here unfortunately at the time. Just wondering if there was a rotation period reported for 2004 BL86?
I checked the Minor Planet Ephemeris Service for this object and it reported that its apparent motion across the sky was in the order of 159 arcsec/min around closest flyby. A quick calculation for my own telescope system with a pixel scale of 2.17 arcsec/pixel indicates that a maximum exposure time of 0.8 seconds was allowable before trailing would occur of the asteroid target! I think this would indeed be a big challenge to obtain good SNR values and even more so for a rotation curve! I am guessing that those in possession of higher end tracking mounts can somehow program the mount to follow the asteroid instead of sidereal rate.
Best wishes and clear skies