<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Pictures for Bernard, plus a quick note for the others:</div><div><br></div><div>In the u filter we have light leaking through the auxiliary filter onto the science array - quite a lot actually, up to 30% of the flux in nearby ccds is leakage.</div><div>The frames OMEGACAM_IMG_OBS214_FLAT0001 and 0002 (from 2011-08-02) are u dome flats. One is normal and in the other one the aux filter on one side was covered with a piece of paper. The difference between the two frames is the light leaking in through the aux filter.</div><div><br></div><div>Attached two pictures. The first is the flat field 1, obtained when the aux filter on the left is covered. The second is the difference between 2 and 1, ie the leaked light. Clearly it comes from the aux filter. The pattern is similar to the Jupiter experiment in comm2. </div><div>Also notice the structure of the difference flat field: it does not show the regular pattern typical of u band flats, instead it is much flatter. This is all consistent with 'g' light leaking into the science ccds through the aux filter.</div><div><br></div><div>This is not nice - but on sky it will not be quite so bad since the sky is not as red as the dome flat lamps...</div><div>K</div><div><br></div><div><br></div><img height="746" width="682" apple-width="yes" apple-height="yes" id="3217d9d0-f21f-447a-ad49-5fadbea17187" src="cid:D7D8AF13-0228-4761-890A-7ADA7A3776A7@pl.eso.org"><img id="c54575ed-c2dd-4f89-817f-8970a078df84" height="746" width="682" apple-width="yes" apple-height="yes" src="cid:07430F74-5D98-47BD-A2B3-531C56FD553C@pl.eso.org"></body></html>