\begin{table}%t1
\par
\caption {\label{table1}Observations used for the study of massive stars in both NGC~2244 and Mon OB2. }
%\centerline
 { \begin{tabular}{l l l l c c c}
\hline\hline                 % inserts double horizontal lines
Object & Cluster & Obs. run & Telescope/Instrument & Wavelength domain & n\# Spectra & $\Delta T$\\    % table heading 
\hline 
\noalign{\smallskip}                       % inserts single horizontal line
   HD~46~056 & NGC~2244  &  Feb. 2006 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &6 &5.02\\      
    &   & Apr. 2007 & SPM -- ESPRESSO/2.20~m & &5&6.00\\
    &   & Nov. 2007 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 1&\dots\\
    &   & Jan. 2008 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &4&3.00\\
    &   & Mar. 2008 & SPM -- ESPRESSO/2.20~m & &1&\dots\\
\hline
   HD~46~149 & NGC~2244  &  Dec. 1994 & Asiago -- Echelle/1.82m & &1&\dots\\
    &   & Dec. 1998 & Asiago -- Echelle/1.82~m & &1&\dots\\
    &   & Jan. 2003 & OHP -- ELODIE/1.93~m & &1&\dots\\
    &   & Nov. 2005 & OHP -- ELODIE/1.93~m & &1&\dots\\
    &   & Jan. 2006 & ESO -- FEROS/2.20~m & &1&\dots\\
    &   & Feb. 2006 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &6&5.10\\
    &   & Apr. 2007 & SPM -- ESPRESSO/2.20~m & & 3&3.97\\
    &   & Apr. 2007 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &1&\dots\\
    &   & Nov. 2007 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 6&25.05\\
    &   & Jan. 2008 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &4&5.03\\
    &   & Mar. 2008 & SPM -- ESPRESSO/2.20~m & &5&4.93\\
    &   & Sep. 2008 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 1&\dots\\
    &   & Oct. 2008 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 3&4.02\\
\hline
   HD~46~150 & NGC~2244  &  Nov. 1999 & OHP -- ELODIE/1.93~m & &1&\dots\\
    &   & Jan.  2003 & OHP -- ELODIE/1.93~m & & 1&\dots\\
    &   & Nov  2004 & OHP -- ELODIE/1.93~m & & 1&\dots\\
    &   & Jan. 2006 & ESO -- FEROS/2.20~m & & 1&\dots\\
    &   & Feb. 2006 & ESO -- FEROS/2.20~m & & 1&\dots\\
    &   & Feb. 2006 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &6&5.10\\
    &   & Apr. 2007 & SPM -- ESPRESSO/2.20~m & & 5&5.99\\
    &   & Nov. 2007 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 5&25.07\\
    &   & Jan. 2008 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &4&2.99\\
    &   & Mar. 2008 & SPM -- ESPRESSO/2.20~m & & 5&3.95\\
    &   & Oct. 2008 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 4&4.00\\
\hline
   HD~46~202 & NGC~2244  & Jan. 2006 & ESO -- FEROS/2.20~m & &1&\dots\\
    &   & Feb. 2006 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &2&1.98\\
    &   & Apr. 2007 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &2&5.00\\
    &   & Nov. 2007 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 4&20.00\\
    &   & Jan. 2008 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &4&3.01\\
\hline
   HD~46~223 & NGC~2244  & Jan. 1999 & OHP -- ELODIE/1.93m & &1&\dots\\
    &   & Nov  2005 & OHP -- ELODIE/1.93~m & & 1&\dots\\
    &   & Jan. 2006 & ESO -- FEROS/2.20~m & & 1&\dots\\
    &   & Feb. 2006 & ESO -- FEROS/2.2~0m & & 1&\dots\\
    &   & Feb. 2006 & OHP -- AURELIE/1.52~m & 5500--5900~\AA & 6&5.03\\
    &   & Apr. 2007 & OHP -- AURELIE/1.52~m & 5500--5900~\AA & 3&6.00\\
    &   & Nov. 2007 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 5&21.98\\
    &   & Jan. 2008 & OHP -- AURELIE/1.52~m & 5500--5900~\AA & 4&3.06\\
    &   & Mar. 2008 & SPM -- ESPRESSO/2.20~m & & 3&2.01\\
    &   & Oct. 2008 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 1&\dots\\
\hline
   HD~46~485 & NGC~2244  & Nov. 2005 & OHP -- ELODIE/1.93~m & & 1&\dots\\
    &   & Jan. 2006 & ESO -- FEROS/2.20m & & 1&\dots\\
    &   & Nov. 2007 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 6&14.99\\
    &   & Jan. 2008 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &4&3.05\\
    &   & Mar. 2008 & SPM -- ESPRESSO/2.20~m & &5&4.02\\
\hline
   HD~46~573 & Mon OB2  & Jan. 2006 & ESO -- FEROS/2.20~m & & 1&\dots\\
    &   & Feb. 2006 & ESO -- FEROS/2.20~m & & 1&\dots\\
    &   & Feb. 2006 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &3&2.97\\
    &   & Apr. 2007 & SPM -- ESPRESSO/2.20~m & & 5&5.99\\
    &   & Nov. 2007 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 6&25.98\\
    &   & Jan. 2008 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &5&3.05\\
    &   & Oct. 2008 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 3&3.00\\
\hline
   HD~46~966 & Mon OB2  & Jan. 2003 & OHP -- ELODIE/1.93m & & 2&1.76\\
    &   & Nov  2004 & OHP -- ELODIE/1.93~m & &1&\dots\\
    &   & Jan. 2006 & ESO -- FEROS/2.20~m & &2&1.94\\
    &   & Feb. 2006 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &6&5.01\\
    &   & Feb. 2007 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &1&\dots\\
    &   & Apr. 2007 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &1&\dots\\
    &   & Nov. 2007 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 5&24.05\\
    &   & Jan. 2008 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &4&3.02\\
\hline
   HD~48~279 & Mon OB2  & Jan. 2000 & OHP -- ELODIE/1.93m & &1&\dots\\
    &   & Nov  2004 & OHP -- ELODIE/1.93~m & &1&\dots\\
    &   & Nov. 2007 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 9&16.02\\
    &   & Jan. 2008 & OHP -- AURELIE/1.52~m & 5500--5900~\AA &4&3.01\\
    &   & Mar. 2008 & SPM -- ESPRESSO/2.20~m & &4&4.01\\
    &   & Oct. 2008 & OHP -- AURELIE/1.52~m & 4450--4900~\AA & 1&\dots\\
\hline
\end{tabular}}
\smallskip
The first and the second columns give the name of the object and the membership to the cluster or association (Ogura \& Ishida  1981). The next columns are the epochs of the campaign, the telescope/instrument used, the observed wavelength domain, the number of spectra obtained and the time elapsed between the first and the last spectrum of the run, expressed in days.
\end{table}