Opened 15 years ago
#1485 new defect
Average Magnitude Error Wrong for Dual PSF Fit
| Reported by: | morganson | Owned by: | eugene |
|---|---|---|---|
| Priority: | normal | Milestone: | |
| Component: | misc | Version: | |
| Severity: | normal | Keywords: | |
| Cc: |
Description
This error was observed in the most recent dvo database release.
We have a source at
215.151440773 -16.0417386404
It's z magnitude measurements are:
# z z:err flag0x extern_id
19.223207 0.053754 2204000 6446648
19.159416 0.043235 2200000 6447248
19.238922 0.035382 6200005 10769549
19.347965 0.048594 2200000 10770809
21.407980 0.230573 2004024 11342113
20.807688 0.133663 6004024 11342113
19.291172 0.035008 6200045 11340493
But the average z z:err:
19.2955150604 0.984078884125
That error is suddenly huge and wrong. In one exposure the source was fit as a pair with a double psf. But the flux does not add up to the flux in all other exposures. I assume that the z error is a standard deviation derived quantity rather than the error in the weighted mean (which should always be smaller than the individual errors). But the magnitudes from the exposure in which the source was (incorrectly) identified as a pair should not be included in the average.
If this happens often, it will be a big problem anytime someone makes mag:err cuts.
