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emhuff / Balrog

DES image simulation software: We dug too deeply and too greedily
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postage stamp size, surface brightness #24

Closed suchyta1 closed 10 years ago

suchyta1 commented 10 years ago

I realized that when I compute the postage stamp size, I'm not doing quite what I thought I was. Sersic.xValue returns surface brightnesses, but the --fluxthresh I was thinking of as being entered as an ADU flux level in a pixel. In the code, --fluxthresh winds up being treated equivalently to xValue, looking if xValue has fallen below --fluxthresh, meaning I actually wind up treating --fluxthresh as a surface brightness. So, the default of 0.01 actually means 0.01 ADU/arcsec^2 for comparing to the profile. This is ~16 times less than the ADU/pixel I was thinking. Fortunately this makes all the postage stamps larger than they need to be, so it's not cutting off all the profiles.

suchyta1 commented 10 years ago

The way the postage stamp is chosen is different now. Galsim does it automatically based on the GSParams. The original message here is no longer relevant.