...
Sources of interest are at (roughly)
| x | y |
|---|---|
| 748 | 3841 |
| 763 | 1580 |
| 1503 | 3083 |
| 3731 | 3854 |
| 3769 | 1626 |
| 4502 | 878 |
| 5227 | 2374 |
Bad smudge ends at y=500 and we don't have a source below y=500.
...
For reasons of time I'm going to skip steps 1,2,3 and run Source Extractor on the four frames, with a tweaked configuration file that requires high significance for detection.
I ran source extractor with this configuration file: sex.config
and this default.sex file: default.sex (note this has an edited value for DEBLEND_NTHRESH, set to 1 here but was 32 for initial results shown below):
sex CU2A60*1.fits
And got this output file, called test.cat:
So that seems good. It caught all 7 sources plus 5 more. All look fairly compact. So why the extra ones, and where are they?
Extract x and y values: Use grep to get rid of comment lines and awk to print column 2. These are x values
cat test.cat | grep -v "#" | awk '{print $2}'
4506.706
772.435
3774.000
792.160
5232.965
5225.302
5239.854
5234.985
1511.580
3739.769
752.534
750.389
Same for y:
cat test.cat | grep -v "#" | awk '{print $3}'
888.634
1602.611
1639.883
1591.234
2393.825
2398.723
2395.239
2402.175
3099.798
3863.995
3849.634
3835.964
Plot x vs y to see where they are:
Ah, OK. So it's finding all 7 sources that we want, but the spiky PSF is making it break ('deblend') them into multiple adjacent sources. We can do one of two things: 1) convolve image with a Gaussian to to smooth out the PSF, or 2) tweak the deblending value that Source Extractor uses to fragment sources. Let's try setting number of deblending levels to 1, edited default.sex file to have
DEBLEND_NTHRESH 1 # Number of deblending sub-thresholds
Re-ran source extraction with this, got this result:
Produce x-ordered listing to compare to expectations:
cat test.cat | grep -v "#" | sort -k 2 -n
This looks good now!
Run on all 4 frames:
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ ls *.fits
CU2A6042.fits CU2A6050.fits CU2A6058.fits CU2A6081.fits
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ sex CU2A6042.fits
----- SExtractor 2.5.0 started on 2022-09-24 at 09:47:41 with 1 thread
Measuring from: "Unnamed" / 6744 x 4502 / 16 bits INTEGER data
(M+D) Background: 511.912 RMS: 122.625 / Threshold: 183.937
Objects: detected 7 / sextracted 7
> All done (in 3 s)
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ mv test.cat CU2A6042.cat
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ sex CU2A6050.fits
----- SExtractor 2.5.0 started on 2022-09-24 at 09:48:02 with 1 thread
Measuring from: "Unnamed" / 6744 x 4502 / 16 bits INTEGER data
(M+D) Background: 511.917 RMS: 122.511 / Threshold: 183.767
Objects: detected 7 / sextracted 7
> All done (in 3 s)
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ mv test.cat CU2A6050.cat
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ sex CU2A6058.fits
----- SExtractor 2.5.0 started on 2022-09-24 at 09:48:21 with 1 thread
Measuring from: "Unnamed" / 6744 x 4502 / 16 bits INTEGER data
(M+D) Background: 511.912 RMS: 122.556 / Threshold: 183.835
Objects: detected 7 / sextracted 7
> All done (in 3 s)
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ mv test.cat CU2A6058.cat
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ sex CU2A6081.fits
----- SExtractor 2.5.0 started on 2022-09-24 at 09:48:49 with 1 thread
Measuring from: "Unnamed" / 6744 x 4502 / 16 bits INTEGER data
(M+D) Background: 511.919 RMS: 122.474 / Threshold: 183.71
Objects: detected 8 / sextracted 8
> All done (in 3 s)
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ mv test.cat CU2A6081.cat
HUIT-FAS-MacBook-Stubbs:Q42022 cstubbs$ wc *.cat
25 267 2500 CU2A6042.cat
25 267 2500 CU2A6050.cat
25 267 2500 CU2A6058.cat
26 285 2683 CU2A6081.cat
30 357 3415 test2.cat
131 1443 13598 total
Ok, so we have one extra source in frame 81. Huh.
I think it found a companion ghost. extract flux values:
cat CU2A6081.cat | grep -v "#" | awk '{print $4}'
make a diagnostic plot of flux vs. x