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I'm playing around with the data in the SDSS DR16, but the magnitudes have huge uncertainties:

for i in ['umag', 'gmag', 'rmag', 'imag', 'zmag']:
    print(max(dataset[i]))

30.889
26.3114
26.5881
29.9517
24.465


for i in ['e_umag', 'e_gmag', 'e_rmag', 'e_imag', 'e_zmag']:
    print(max(dataset[i]))


2661440.0
37.8006
25.9054
2392490.0
113.926

Why are the errors so large? Could they be millimags? But even then, e_umag and e_imag are enormous, compared to the measurements. A comment on this question states that errors should be ~0.01.

Jim421616
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  • Why are you printing the maximum value (which will most probably be a large number). – ProfRob Apr 06 '22 at 20:54
  • Error is quoted as being in the range [1.5e-5...100] in the Vizier table with '100' being set in the event of issues in the fit so max() is definitely not going to give a representative value for the typical magnitude error – astrosnapper Apr 06 '22 at 21:04
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    My question is why are they so large, especially if the range is supposed to be [1.5e-5...100] ? – Jim421616 Apr 06 '22 at 21:50
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    100 is being used in this instance as a replacement for null/missing/bad values; not all table formats support the concept of null values. – astrosnapper Apr 07 '22 at 17:02

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