Zeropoints were determined by Kate Whitaker, using all standard stars
taken on photometric nights during run #1.
The zeropoints were remarkably stable; no effort has been made to
correct for airmass or other effects. The error in the zeropoints is
probably about 0.02.
<p>
<table>
<tr><th>Filter</th><th>ZP</th>
</tr>
<tr><td>J1</td><td>22.66 (22.65)</td></tr>
<tr><td>J2</td><td>22.52 (22.52)</td></tr>
<tr><td>J3</td><td>22.41 (22.43)</td></tr>
<tr><td>H1</td><td>22.30 (22.28)</td></tr>
<tr><td>H2</td><td>22.18 (22.17)</td></tr>
<tr><td>Ks</td><td>22.01 (22.01)</td></tr>
</table>
<p>
Values in brackets are the ones that PvD derived 'by hand' after the first
night of the run.
The zeropoints are in Vega - see <a href="../instrument/filters.html">
Instrument: Filter info</a> for AB zeropoints. Vega magnitudes can
be calculated by<p>
mag = ZP - 2.5*log(ADU) + 2.5*log(exptime)
<p>