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For various reasons, there can be several entries for a given stack object. See the page describing for suggested approachesThe best way to select the best entry is to use the PrimaryDetection column in StackObjectThin. 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 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). In severe cases, there may be more than 2 entries with PrimaryDetection=1. 

There is also a BestDetection flag in StackObjectThin, which has even more issues than PrimaryDetection, and we recommend to not use it at the current time. Both PrimaryDetection and BestDetection flag will be improved in DR2.

PS1 astrometry

How good is PS1 astrometry?

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