Hi Bruce, ah I see, so you’re using the filters from Larsair. I’m looking through the schema and objects.jdmin should indeed provide the “Earliest Julian Day of candidates that cite this object”, but I’m not sure if the JDNOW() function is predefined? Let’s also ping @roy to see if you can help out with this.
Lasair filters on the objects, not the candidates. To get the first candidate, you will need to get relevant object, then look at its candidates (web or API). To get a new orphan object, I suggest objects.jdmax < jdnow()-3 AND objects.ncand=1.
The attribute jdmin in lasair-ztf has always been misunderstood, its actually the earliest candidate from the 30-day lightcurve that we get with the alert. So there can be earlier detections, but the alert did not include them. We have asked Rubin to add an attribute firstDiaSourceMJD which is the real time of the first diaSource.