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\begin{document}
\title{\textbf{Practice Work Session P5 (2h)}\\Preparation of observation}
\author{G.\ Duvert,\\
        Laboratoire d'Astrophysique de Grenoble (LAOG)}
\date{\textbf{Euro Summer School}\\
  \emph{Observation and Data reduction with the Very Large Telescope
    Interferometer} \\
4-16 June 2006, Goutelas (France)}
\maketitle

\begin{abstract}
 This Practice Work Session focusses on the selection of a good
 calibrator for interferometric observations. The SearchCal tool (SC)
 is used as an example. 
\end{abstract}

\section{Setup}
The session will use the local server (http://192.168.8.119) since the
SC application works only on a client-server basis. From the Mozilla
web browser, open the http://192.168.8.119 website and start the web
version of aspro (``start the application launcher applet''). Do not
use authentication. A ``Choose...'' menu appears. 
Select the full ASPRO interface.

The documentation for SC is included in the ASPRO documentation and is
provided on the school website.

\section{starting SC}
We will use the ``WHERE'' and ``WHAT'' menus, defining first the
interferometer (VLT~2T~+~Amber).

We will find first the calibrators for Achernar in K (2.1$\mu$).
\begin{itemize}
\item Retrieve the CDS coordinates of Achernar, akcnowledge the values.
\item Open the ``Search Calibrators'' menu item.
\item Note that the max baseline length is given as an information.
\item Achernar's K magnitude is 0.88.
\item Change Min\&Max magnitudes to -1 3 to bracket the object's
  magnitude (why?).
\item GO
\end{itemize}

The server side of the program queries the various
catalogs. Hopefully, if the CDS answers arrive in a reasonably short
time, a result panel appears.
\section{the result panel\label{thelabel}}
How many stars were found? How many selected? What was the reasons
several stars were not selected? Why such a small number
of calibrators?

Colors in list: they have a meaning. For example, what is the
originating catalog for the JHK magnitudes of HD14641? What is the
confidence index of the corresponding visibility? Why such a low (far
from V=1.0) visibility?


\section{Other buttons}

Use the ``SHOW DETAILS'' button to see all information. Use the ``SHOW
ALL RESULTS'' to see a complementary list of stars that were not
selected as good calibrators because of their multiplicity or
variability flags.

\section{MIDI calibrator}
We will now find the calibrators for Achernar, but observed with MIDI
at 10$\mu$. Select MIDI+UT, recall the ``Search Calibrators...'' menu,
enter the Achernar 10$\mu$ magnitude: -1. The panel is sligtly
different. Get the result. Discuss.

The calibrator found is closer than at K, and has a better
visibility. Why?

\section{Fainter Star, K band}
Let's go back to VLTI+AMBER, in K band, but with a fainter star, Gl551
(take mag K 5.28).

Fainter stars are more numerous, we will restrict ourselves to a
search zone of 20 minutes of time in RA and 2 degrees in declination.


Same questions as in section~\ref{thelabel}. The visibilities are now
better (for a calibrator). Why? What would be your final choice in
that list for the Gl551 star?

Use the ``sort above list'' subpanel to sort the list according to the
various sorting parameters.

\end{document}
