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I saw that some survey said that their depth is 27.5 magnitudes.

May I ask that if I have a dataset with magnitude and their errors, for example I have J band j_m, j_cmsig, j_msigcom, j_snr from Sextractor.

How can I derive the 3 sigma magnitude depth in this fields to compare with the other survey.

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It's the magnitude where the average signal-to-noise ratio (I assume that's what j_snr represents) is 3.

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  • $\begingroup$ Is this possible to calculate from j magnitude and their error? $\endgroup$ – GHC Oct 12 '20 at 7:19
  • $\begingroup$ @GHC No. And notice that magnitude uncertainties are generally non-linear and asymmetric, particularly when large. $\endgroup$ – ProfRob Oct 12 '20 at 10:30
  • $\begingroup$ May I ask that what the different if I need to get the depth in 5sigma/2arcsec? So I can plot the SNR and get the SNR to 5, but what the meaning of 2arcsec. $\endgroup$ – GHC Oct 14 '20 at 10:16

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