From: Michael Wood-Vasey (wmwood-vasey@lbl.gov)
Date: Tue Nov 05 2002 - 10:39:45 PST
On Tue, Nov 05, 2002 at 12:51:46AM -0800, Saul Perlmutter wrote:
> The listed magnitudes in sntrak are i'_AB for this run. We don't yet know
> how uncertain these numbers are in their zeropoint, but you can estimate
> their photometric uncertainty from their Ap.Sig.
It anyone's curious these zeropoints were obtained from calibration
against fields from the SDSS Early Data Release. Brian Lee estimates
the uncertainty in the magnitudes from those fields at 5% in i'. If
it helps to get a sense of the calibration, we had standard star
observations at airmasses of 1.088 and 1.919, but we could not fit an
airmass term and just assumed a standard one. Rob may have more
opinions about this, but I think we're pretty confident that we're
right to within a couple tenths of a magnitude.
- Michael
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