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For various reasons, there can be several entries for a given stack object. The  Currently, the best way to select the best a unique entry is to use the PrimaryDetection column in in StackObjectThin, which is a geometric flag which defines assigns a unqiue unique area on the sky to each skycell. However, in about 0.5% of the stack objects, there are multiple entries with PrimaryDetection=1 for a given object. This happens when there is a very close split stack detection on the primary skycell. The PrimaryDetection flag is then set for both entries because both detections are in the primary skycell (for that location on the sky) and both are assigned to the same object. In severe cases, there may be more than 2 entries with PrimaryDetection=1. It is also possible for an object to exist without a PrimaryDetection=1 detection if it lies in an area overlapping an adjacent skycell but is not detected on the primary skycell, only on the non-primary one(s) (e.g. this might happen for an object very near the detection limit, or if there was some masking only on the primary skycell).

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