CAT Night-to-Night Overlap Analysis

Night-to-Night Overlap Analysis for Final Catalog Point Sources

This analysis examines the night-to-night point source internal consistency of photometry and astrometry. It utilizes information from the scan-to-scan overlap regions where each scan in the scan pair are from different nights or different night-hemis. 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 over the full sky (FSky) and at hemisphere seams (Hemis) .

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.

Night-to-night overlap analysis is shown for non-pole scan, pole scans and full set of night-to-night scan pairs (pole plus non-pole).

Summary tables comparing the statistical results from full sky, non-pole and pole is here.

Night-to-Night Pole plus Non-pole

The following histograms represent night to night overlaps from the entire sky, pole plus non-pole scans.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

The tables below gives the mean and standard deviation from the full sky night-to-night histograms:

Table A: Statistics for Night-to-Night Scan Overlaps - Point Source Final Catalog Pole plus Non-pole (SNR20)
Average Delta count > 1 count >= 100
Mean Std Mean Std
J Mag -.00063 .027 .00039 .019
H Mag -.00066 .025 -.00025 .017
K Mag .00023 .026 -.00015 .017
Ra(arcsec) .0033 .128 -.00385 .048
Dec(arcsec) -.00682 .121 -.00109 .068

Table A: Statistics for Night-to-Night Scan Overlaps - Point Source Final Catalog Pole plus Non-pole (SNR20)
Average Delta	count > 1	count >= 100
Mean	Std	Mean	Std
J Mag	-.00063	.027	.00039	.019
H Mag	-.00066	.025	-.00025	.017
K Mag	.00023	.026	-.00015	.017
Ra(arcsec)	.0033	.128	-.00385	.048
Dec(arcsec)	-.00682	.121	-.00109	.068

Night-to-Night Non-pole Scans Only

The following histograms represent night to night overlaps from the non-pole scans only.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Outliers in the non-pole overlap histograms have been identified. One pair of scans has average delta magnitudes greater than .2 in all bands. There are three other scan pairs that have average delta J magnitude between .1 and .15. All of these outlier pairs are expained in here .

The tables below gives the mean and standard deviation from the non-pole only histograms:

Table B: Night-to-Night Statistics for Scan Overlaps - Point Source Final Catalog Non-pole (SNR20)
Average Delta count > 1 count >= 100
Mean Std Mean Std
J Mag -.00018 .025 .000087 .019
H Mag -.00029 .024 -.00039 .018
K Mag .0000998 .024 -.00024 .017
Ra(arcsec) -.0054 .095 -.00478 .047
Dec(arcsec) -.000488 .101 -.00126 .066

Table B: Night-to-Night Statistics for Scan Overlaps - Point Source Final Catalog Non-pole (SNR20)
Average Delta	count > 1	count >= 100
Mean	Std	Mean	Std
J Mag	-.00018	.025	.000087	.019
H Mag	-.00029	.024	-.00039	.018
K Mag	.0000998	.024	-.00024	.017
Ra(arcsec)	-.0054	.095	-.00478	.047
Dec(arcsec)	-.000488	.101	-.00126	.066

Night-to-Night Pole Scans Only

The following histograms represent night to night overlaps from the pole scans only.

Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

The tables below gives the mean and standard deviation from the pole only histograms:

Table C: Night-to-Night Statistics for Scan Overlaps - Point Source Final Catalog Pole Only (SNR20)
Average Delta count > 1 count >= 100
Mean Std Mean Std
J Mag -.0015 .029 .0034 .017
H Mag -.0015 .037 .0014 .014
K Mag .00098 .030 .0011 .013
Ra(arcsec) .020 .174 .0054 .054
Dec(arcsec) -.019 .150 .0007 .078
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Table C: Night-to-Night Statistics for Scan Overlaps - Point Source Final Catalog Pole Only (SNR20)
Average Delta	count > 1	count >= 100
Mean	Std	Mean	Std
J Mag	-.0015	.029	.0034	.017
H Mag	-.0015	.037	.0014	.014
K Mag	.00098	.030	.0011	.013
Ra(arcsec)	.020	.174	.0054	.054
Dec(arcsec)	-.019	.150	.0007	.078

Night-to-Night Table Summary

Night-to-Night Overlap Statistics SNR20 Counts > 2
Average Delta	FSky		Non-pole		Pole
Average Delta	Mean	Std	Mean	Std	Mean	Std
J Mag	-.00063	.027	-.00018	.025	-.0015	.029
H Mag	-.00066	.025	-.00029	.024	-.0015	.037
K Mag	.00023	.026	.0000998	.024	.00098	.030
Ra(arcsec)	.0033	.128	-.0054	.095	.020	.174
Dec(arcsec)	-.00682	.121	-.000488	.101	-.019	.150

Night-to-Night Table Summary for Counts >= 100

Night-to-Night Overlap Statistics SNR20 Counts >= 100
Average Delta	FSky		Non-pole		Pole
Average Delta	Mean	Std	Mean	Std	Mean	Std
J Mag	.00039	.019	.000087	.019	.0034	.017
H Mag	-.00025	.017	-.00039	.018	.0014	.014
K Mag	-.00015	.017	-.00024	.017	.0011	.013
Ra(arcsec)	-.00385	.048	-.00478	.047	.0054	.054
Dec(arcsec)	-.00109	.068	-.00126	.066	.0007	.078

[Last Updated: 2002 Oct 30; by Sherry Wheelock]

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