[Comm2011] Fwd: Re: Distorsion, crosstalk, tilt: outlook for OCAM 1B

[Gijs Verdoes Kleijn]

-------- Originele bericht --------
Onderwerp: 	Re: Distorsion, crosstalk, tilt: outlook for OCAM 1B
Datum: 	Fri, 01 Apr 2011 19:56:02 +0200
Van: 	Dietrich Baade <dbaade at eso.org>
Aan: 	Gijs Verdoes Kleijn <verdoes at astro.rug.nl>
CC: 	K Kuijken <kuijken at strw.leidenuniv.nl>, Muschielok Bernard 
<mbernard at usm.uni-muenchen.de>



Hi Gijs,
>  We are of course very interested to hear the outcome of last nights
>  work on the distorsions (i.e., anisotropy of the PSF), cross-talk and
>  saturation. If you find the time in your busy schedule.
Thanks very much for your interest.

Since I haven't seen a reply from others, let me try:

PSGF and cross talk are being investigated.  Saturation looks OK now.

>  Let us know where we can help out today with additional analysis. We
>  expect the data in this afternoon.
Right now, three things are at the top of my curiosity list:

1)  A couple of nights ago, Bernard made three consecutive images of a
standard star field with exposure times of 1, 3, and 9 units (I forget
what "unit" was and don't know the file names).  Their aim is to
determine non-linearity from point sources rather than FF's.  This can
be done by boot-strapping the calibration from the tabulated standard
magnitudes.  But one can also compare the three exposures of all
suitable stars in the filed.  The latter avoids all problems with
extinction, etc (the night was photometric).

2)  Ewout and Thomas Szeifert independently determined a drop in gain
from 2.2 to 1.6 e-/ADU after a change of the filter settings in FIERA.
However, the true gain should not be appreciably affected by reduced
filtering.  However, it could be spurious if the filtering also affects
subsequent pixels, so that their noise becomes correlated.  Could you
try to simulated this in some simple way (for instance by smoothing a
bias image in the row direction only) and see whether and how this
affects the deduced gain?

3)  In your previous tests, have you seen any crosstalk between CCDs
94-96 (on the RTD, they are the 3 CCDs at the right end of the top
row)?  If yes, what symptoms do you see?

Many thanks in advance if you can look into this.

>  Tilt and PSF anisotropy can have an effect on the OCAM 1B schedule.
>  What is the opinion on the mountain regarding this?

I've asked Ueli Weilenmann to make a proposal.  My _opinion_ is that we
should not change the start date.  We could add 1 day to the duration.

>  Please let us know if can help there with further analysis.
>
>  Best wishes, om behalf of the Groningen team,
>  Gijs
>


-- 
Dietrich Baade
ESO - European Organisation for Astronomical Research in the Southern Hemisphere
Karl-Schwarzschild-Strasse 2,  85748 Garching bei Muenchen,  Germany
Email: dbaade at eso.org    Tel: +49 89 3200-6388    Fax: +49 89 3202362



-- 
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|dr Gijs Verdoes Kleijn         |   astronomer                     |
|e-mail: verdoes at astro.rug.nl   |   OmegaCEN / Kapteyn Institute / |
|www: www.astro.rug.nl/~verdoes |   Target                         |
|tel: +31-50-3638326            |   University of Groningen        |
|mobile: +31-654658050          |   postal address:                |
|                               |   Kapteyn Astronomical Institute |
|                               |   Postbus 800, 9700 AV, Groningen|
|                               |   The Netherlands                |
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