Overlap Analysis for Final Catalog Point Sources
This analysis examines the point source internal consistency of photometry and astrometry over the full sky (FSky) utilizing information from the scan-to-scan overlap regions. Computations made during the duplicate resolution process provide mean delta magnitudes and mean delta RA and Dec for each overlap scan pair. Confused sources were NOT included in this analysis and all sources had SNR > 20. Links to additional analysis provide information regarding internal consistency at hemisphere seams (Hemis) and for night-to-night (N2N) consistency.
Tables summarizing statistical results from full sky (FSky), night-to-night (N2N) and hemisphere (Hemis) overlap scans are found here.
Sources with SNR > 20, where SNR is computed as 1.0857/sigma_mag, were selected within an overlapping scan pair. The difference in magnitude and position was computed for each matching (within 2") source pair. An average delta [J,H,K] magnitude and average delta RA and DEC were computed for each overlapping scan pair. Histograms were made of these averages. Two populations are shown on each histogram. The BLACK histogram incorporates all overlapping scan pair averages where at least 2 matched sources contributed to the average. The BLUE histogram reflects only the overlapping scan pair averages where at least 100 matched sources contributed to the average.
A mean and standard deviation for each distribution were computed and printed on the histogram. The left most statistical group reflects the distribution where the number of match sources > 1 in the overlap regions. The statistical group on the right reflects the distribution where the number of match sources contibuting to the average >= 100. Table A is a summary of the distribution statistics.
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| Figure 1 | Figure 2 | Figure 3 | Figure 4 | Figure 5 |
| Average | count > 1 | count >= 100 | ||
|---|---|---|---|---|
| Mean | Std | Mean | Std | |
| Delta J Mag | .00105 | .02 | .0025 | .014 |
| Delta H Mag | .00216 | .019 | .004 | .015 |
| Delta K Mag | .00068 | .018 | .00013 | .014 |
| Delta Ra(arcsec) | .00292 | .084 | -.0022 | .04 |
| Delta Dec(arcsec) | -.00704 | .090 | -.005 | .056 |
[Last Updated: 2002 Oct 30; by Sherry Wheelock]
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