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Appendix B: limiting magnitudes

Three-sigma limiting magnitudes were determined by measuring the RMS on each final stacked mosaic using the following expression:

\begin{displaymath}
m_{lim} = -2.5 \cdot log \Big( \frac{3 \cdot RMS \cdot Pix\_A}
{T_{exp}} \Big) - k \cdot X + Z
\end{displaymath}

where Z, X and k are the correspondent zero point, airmass and extinction coefficient respectively, $Pix\_A$ is the PSF pixel area, and Texp is the exposure time. For the OACDF, the typical PSF FWHM is about 1'', which corresponds to a $Pix\_A$ of 14 pixels. The three-sigma limiting magnitudes for the OACDF observations are summarised in Table 1. Note that the exposure time in the above equation is the one of the single dithering (column 4 in Table 1), whereas the RMS is the one measured in the stacked mosaic image.



Juan Alcala
2002-02-05