The sky is quite variable. The values below are the average sky
level and its 1 sigma variation as measured from data of the first
run. The variation is measured by comparing the average sky levels
in sequences of 1-1.5 hr in length; the variation on shorter timescales
can be substantially higher.
<p>
<table>
<tr>
<th>Filter</th><th>median</th><th>rms</th></tr>
<tr><td>J1</td><td>22</td><td>5</td></tr>
<tr><td>J2</td><td>40</td><td>8</td></tr>
<tr><td>J3</td><td>65</td><td>13</td></tr>
<tr><td>H1</td><td>205</td><td>57</td></tr>
<tr><td>H2</td><td>216</td><td>35</td></tr>
<tr><td>K</td><td>494</td><td>53</td></tr>
</table>
<p>
These are ADU per pixel per second.