\begin{table}%t1
  \caption{\label{tab:1415h}Rotational transition frequencies and spectroscopic constants of N$^{15}$NH$^+$.}
  \small%\centerline
{
  \begin{tabular}{ccccc}
    \hline\hline\noalign{\smallskip}
    $J'$ & $J$ & {Observed} & {Obs.-calc.} & {Uncert.$^{{a}}$} \\
         &     & {(MHz)}    & {(kHz)}	   & {(kHz)}	       \\
    \hline  \noalign{\smallskip}
    1  &  0  &   91~205.7380$^{{b}}$ & 43.5 & 50 \\
    3  &  2  &  273~608.9846           & --2.9 &  5 \\
    4  &  3  &  364~802.5417           &  3.8 &  5 \\
    5  &  4  &  455~987.9927           &  0.6 &  5 \\
    6  &  5  &  547~163.3276           &  1.4 &  5 \\
    7  &  6  &  638~326.5101           & --6.0 &  5 \\
    8  &  7  &  729~475.5408           &  3.0 &  5 \\
    \noalign{\smallskip}
    \mcl{5}{l}{rms$_{\rm res}$$^{{c}} = 16.7$~kHz}\\
    \mcl{5}{l}{$\sigma^{d} = 0.846$} \\
    \hline  
    \mcl{2}{l}{Constant$^{{e}}$} & &
    \mcl{2}{r}{Correlation matrix} \\
    \hline  
    \mcl{2}{l}{$B_0$ / MHz} &  45~603.01594(41) & 1.000 \\
    \mcl{2}{l}{$D_J$ / kHz} &       84.3346(42)  & --0.928 & 1.000 \\
    \hline
  \end{tabular}}
\smallskip
   $^{{a}}$ Uncertainties estimated as explained in the text.\\
   $^{{b}}$ From \citet{Gudeman-PhDTh82}.\\
   $^{{c}}$ Rms error of residuals: $\sqrt{\frac{\sum {\rm residual}^2}{{N\;{\rm observations}}}}$.\\
   $^{{d}}$ Fit standard deviation: $\sqrt{\frac{\sum {\rm (residual/uncert.)}^2}{{\rm degrees\;of\;freedom}}}$.\\
  $^{{e}}$ Standard errors are reported in parentheses in units of the last quoted digits.
\end{table}