See this Comm Center thread by Geoff Stone. If a minor planet is being acquired via MPCORB lookup, it will have "MP " in front of its name, number, or designation. Remove the MP brom the name before using it as the FITS 'OBJECT' header in images.
As of the changes in ACP-1606 it's even worse. Need to isolate the Planet number, name or designation from both the CT and from the possible trailing stuff after the # Easy. Just use the contents of the Observation.Planet field!