<p>
oops I forgot:
</p>
<p>
the r band 32 band was also observed.
</p>
<p>
Gijs: when did you observe the rotator TWILIGHTS in r?
</p>
<p>
GS
</p>
<p>
On Thu, 16 Jun 2011 13:30:36 +0200, Gert Sikkema wrote:
</p>
<blockquote style="padding-left: 5px; border-left: 2px solid #1010ff; margin-left: 5px; width: 100%">
        <p>
        dear all,
        </p>
        <p>
         I made a list of all 32 CCD pointings observerd so far:
        </p>
        <p>
        B,V, u, g(2x), i, z(2x)
        </p>
        <p>
        g and z were observed two times, but the first of each of these bands was done with cirrus in the sky, this can at least be seen in my analysis of g.
        </p>
        <p>
        I also analyzed the u band data of SA113, but the resulst of this do not make any sense ( I included both gain and/or QE corrections), I do not see a smooth picture, but many discrete off-sets of magnitudes between chips.
        </p>
        <p>
        , I can think of several causes:
        </p>
        <p>
        -) it may be due to bad observing conditions (zeropoints of chips fluctuating),
        </p>
        <p>
        -) the flat field used is not OK (only twilights, remember that the dome flats are useless)
        </p>
        <p>
        -) the QE has a large gradient as a function of wavelength at low wavelengths, my correction based the 360 nm part of table 2.A.1 of Fabrice his thesis may not be a good estimate of the QE.
        </p>
        <p>
        -) another possibility is that the standard star catalog is not really good here (however the scatter was only ~0.05 mags for each chip using ~30 standard stars )
        </p>
        <p>
        So...if you have some time left it may be a good idea to re-observe in the u band in good conditions at SA107
        </p>
        <p>
        ---------------------------------
        </p>
        <p>
        ROTATOR ANGLE
        </p>
        <p>
        another point I would like to verify with you concerns the rotator angle:
        </p>
        <p>
        the illumation variations of the astronomical objects in a reduced science frame are mainly caused by the (twilight) flat fields used.
        </p>
        <p>
        This means that the illumination correction is only dependend on the rotator angle of the twilight flat field and not on the rotator angles of the science frames
        </p>
        <p>
        Not that a varying illumination will also occur in the sky background --> this DOES depend on the rotator angle of the science frames. Deviding this with an (twilight) flatfield with another rotation angle will cause some strange effects on the sky background.
        </p>
        <p>
        So if we want to use a default illumination correction frame in the future, this should mean that the twilight frames in observing mode should always have a similar rotation angle as the ones used for the twilight flatframes that were used to calculate the default illumination correction frame...
        </p>
        <p>
         Gert S.
        </p>
        <p>
        <br />
        On Thu, 16 Jun 2011 13:08:48 +0200, Gijs Verdoes Kleijn wrote:
        </p>
        <blockquote style="padding-left: 5px; border-left: 2px solid #1010ff; margin-left: 5px; width: 100%">
                <p>
                Dear all,
                </p>
                <p>
                
                </p>
                <p>
                Main points of what we have observed:
                </p>
                <p>
                -domeflats r at 4 rotator angles to accompany their twilight counterparts of yesterday.
                </p>
                <p>
                -photometry with ADC in+out
                </p>
                <p>
                -AO/guiding test observation, which includes pointings on Hercules.
                </p>
                <p>
                -daily calibrations
                </p>
                <p>
                
                </p>
                <p>
                Last afternoon we said goodbye to John.
                </p>
                <p>
                
                </p>
                <p>
                Best wishes, Gijs
                </p>
                <p>
                
                </p>
        </blockquote>
        <span id="_rc_sig">
        <pre>
        dr. Gert Sikkema
        Kapteyn Institute Zernike Building, room 133,
        P.O. Box 800 9700 AV Groningen
        sikkema@astro.rug.nl
        homepage: http://www.astro.rug.nl/~sikkema
        31-50-3634548
        Popular lectures on:
        - Einstein's theory of Relativity
        - Globular Clusters
        - Active Galactic Nuclei
        </pre>
        </span>
        <p>
        
        </p>
</blockquote>
<p>
</p>