The upper boxes show the relation between the signal-to-noise ratio 
and the counts (the signal). The values are derived from telluric standard stars 
acquired in slit mode. The values are extracted from different wavelength regions
known to be free of telluric features. 
</font><p><font size="2">
The lower boxes show the relation between the isquere of the signal-to-noise ratio 
and the counts (the signal).  This is to show deviation from the square root
law. 
</font><p><font size="2">
<!--

In addition all data from 2015 have been fit with the following  function:
</font><p><font size="2">
<b> f(x) = a + d * x + b * sqrt( c * x )</b></font><p><font size="2"> 
where <b>a</b> is negligible constant, <br>
<b>b * sqrt( c * x )</b> accounts for the physical effect of photon noise following poission statistcics and <br>
<b>d * x</b> accounts for the technical effect of non-linearity of the detector which influences the S/N at higher counts.</font><p><font size="2">

The coeffients used are:
</font><p><font size="2">
 
VIS, 600 nm<br>
a               = -19.9134           <br>
b               = 1.44183            <br>
c               = 1.21564            <br>
d               = -0.000637029       <br>
</font><p><font size="2">
VIS-arm, 700 nm<br>
a               = -25.4216           <br>
b               = 1.54694            <br>
c               = 1.27896            <br>
d               = -0.000720955       <br>
</font><p><font size="2">
VIS-arm, 990 nm<br>
a               = -18.7537           <br>
b               = 1.30422            <br>
c               = 1.13469            <br>
d               = -0.00042295        <br>

</font><p><font size="2">
The lower three boxes show as a comparison the same relation for flux standard stars, which
are much fainter.
--!>