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Photometry annulus

DJOD · 138

Hors ligne DJOD

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le: avril 07, 2019, 06:33:27 06
Hi all

I am using SIRIL for photometry for variable stars.  While the settings allow you to set the diameter of the inner and outer annulus to measure the background, the measuring circle for the actual star appears to be a fixed size.  If the star being measured is bigger than the measuring circle, this would give incorrect results.

Here is an example image: https://1drv.ms/u/s!Ag0gndakb7fDhLJ6mSYibS8mLccubg

Or am I missing something?

Kind regards
David
« Modifié: avril 07, 2019, 06:36:55 06 par DJOD »

Clear skies
David
Brisbane, Australia


Hors ligne lock042

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Réponse #1 le: avril 07, 2019, 08:15:45 08
The size of circle is updated with fwhm size.
We are doing a psf model on it. It is more complicated than a simple circle arround. So the annulus drawned is not exaclty the annulus where pixel are picked. It's much more complicated ;).
« Modifié: avril 07, 2019, 09:02:52 09 par lock042 »



Hors ligne DJOD

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Réponse #2 le: avril 17, 2019, 07:57:52 07
Thanks for the information.  That certainly helps.  Do you have any description of the process you use?  I am working with a high school group who are learning photometry, and being able to explain some of this would be helpful.  For example, if the FWHM was 2.5, what size measuring circle would you use and how is it calculated?

Clear skies
David
Brisbane, Australia


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Réponse #3 le: avril 17, 2019, 09:24:20 09
Hello, thanks to you I think I will make some changes in the calculation of the annulus for the next version (available very soon).
Also the annulus will be drawn precisely.





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Réponse #4 le: avril 17, 2019, 11:43:12 11
Great.  I look forward to working with the new version when it is available.

Clear skies
David
Brisbane, Australia


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Réponse #5 le: avril 17, 2019, 12:25:08 12
Results will not be very different. But the circule is now accurate.