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SExtractor in Double Image Mode
09-01-2006, 18:58
Post: #1
SExtractor in Double Image Mode
Hello - can anyone help? I am very confused by the behaviour of SExtractor in double image mode. Here is a transcript of what happens:

~> sex FLS51he2_4.fit -c he24.sex
Measuring from: "FLS51 he2" / 2108 x 4157 / 32 bits FLOATING POINT data
Background: 0.0881718 RMS: 0.00269397 / Threshold: 0.00269397
Objects: detected 5806 / sextracted 4085
> All done
~> mv test.cat FLS51he2_4_ap3.cat
~> sex FLS51he2_4.fit,FLS51g_4.fit -c g4.sex
Detecting from: "FLS51 he2" / 2108 x 4157 / 32 bits FLOATING POINT data
Background: 0.0881718 RMS: 0.00269397 / Threshold: 0.00269397
Measuring from: "FLS51 g" / 2108 x 4157 / 32 bits FLOATING POINT data
Background: 1.23659 RMS: 0.0110686 / Threshold: 0.0110686
Objects: detected 5806 / sextracted 4086
> All done
~>

As you can see, detecting sources on the same image, it extracts DIFFERENT NUMBERS OF SOURCES!?!?!?! Shouldn't these two numbers always be the same, thus enabling colour data (for example) to be easily extracted since the ID numbers in both filters are then the same? The catalogues that it produces also get mixed up with some sources not appearing in others. Can you please help? How can i get the same sources extracted in the same order from both files?
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09-02-2006, 14:39
Post: #2
RE: SExtractor in Double Image Mode
Yes this is an old "feature" (OK let's call it a bug :rolleyesSmile, related to various buffer and parameter handling limitations. Could you try to run the single image in "pseudo-double image mode":
sex FLS51he2_4.fit,FLS51he2_4.fit -c he24.sex

One question: what is the difference between he24.sex and g4.sex?
- Emmanuel.
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09-04-2006, 10:51
Post: #3
RE: SExtractor in Double Image Mode
~> sex FLS51he2_4.fit,FLS51g_4.fit -c he24.sex
Detecting from: "FLS51 he2" / 2108 x 4157 / 32 bits FLOATING POINT data
Background: 0.0881718 RMS: 0.00269397 / Threshold: 0.00269397
Measuring from: "FLS51 g" / 2108 x 4157 / 32 bits FLOATING POINT data
Background: 1.23659 RMS: 0.0110686 / Threshold: 0.0110686
Objects: detected 5806 / sextracted 4085
> All done
~>

The difference between he24.sex and g4.sex is only the zeropoint, seeing and ah i think i've found the problem... PHOT_APERTURES is set differently in he24.sex... How strange! What is the reason for this?

~> sex FLS51he2_4.fit,FLS51g_4.fit -c he24.sex
Detecting from: "FLS51 he2" / 2108 x 4157 / 32 bits FLOATING POINT data
Background: 0.0881718 RMS: 0.00269397 / Threshold: 0.00269397
Measuring from: "FLS51 g" / 2108 x 4157 / 32 bits FLOATING POINT data
Background: 1.23659 RMS: 0.0110686 / Threshold: 0.0110686
Objects: detected 5806 / sextracted 4086
> All done
~>
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09-04-2006, 10:55
Post: #4
RE: SExtractor in Double Image Mode
Sorry yes, here is pseudo double image mode...

~> sex FLS51he2_4.fit,FLS51he2_4.fit -c he2blob4.sex
Detecting from: "FLS51 he2" / 2108 x 4157 / 32 bits FLOATING POINT data
Background: 0.0881718 RMS: 0.00269397 / Threshold: 0.00269397
Measuring from: "FLS51 he2" / 2108 x 4157 / 32 bits FLOATING POINT data
Background: 0.0881718 RMS: 0.00269397 / Threshold: 0.00269397
Objects: detected 5806 / sextracted 4086
> All done
~>

Thanks for your help Emmanuel!
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12-21-2015, 16:52
Post: #5
RE: SExtractor in Double Image Mode
(09-02-2006 14:39)Emmanuel Bertin Wrote:  Yes this is an old "feature" (OK let's call it a bug :rolleyesSmile, related to various buffer and parameter handling limitations. Could you try to run the single image in "pseudo-double image mode":
sex FLS51he2_4.fit,FLS51he2_4.fit -c he24.sex

One question: what is the difference between he24.sex and g4.sex?
- Emmanuel.

Hi,

I'm have the same problem, but the parameters PHOT_APERTURE are the same in both files. What should I do?
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