\begin{table}%t5
   \caption{Polarization and infrared emission data for gas-rich comets observed
   at large phase angles.   \label{tab5}}
%\centerline
{\begin{tabular}{llllllll}
   \hline \hline
   Comet name & $\alpha_{\rm obs}^{1}$ & Diaphragm size& $P_{\rm obs}^{2}$ & $P_{\rm dust}^{3}$
   & Polar. & Overheat/silicate & Ref.$^{4}$\\
   & ($^{\circ}$) &  or box (km$^2$) & (\%) & (\%) & class & features at 10 $\mu$m &\\ \hline
   C/1975 N1 (Kobayashi- & 95.4 & $\pi \times 38360^2$ & 9.1 & 25.9 & low & 1.08/no & 1, 2\\
   Berger-Milon)\\
   23P/Brorsen-Metcalf & 86.0 & $\pi \times 37660^2$ & 15.3 & 25.2 & low & 1.05/no &
   1, 3\\
   C/1982 M1 (Austin) & 94.1 & $\pi \times 45000^2$ & 9.1 & 25.9 & low & ?/? & 4, --\\
   & 98 & 2452$~\times~$5655 & 22.3 & 25.8 & high & & 5, --\\
   C/1983 H1 (Iras- & 92.5 & $\pi \times 800^2$ & 32 & 25.8 & high & 1.07/very weak &
   6, 7\\
   Araki-Alcock)\\
   \object{27P/Crommelin} & 73.7 & $\pi \times 28760^2$ & 11.3 & 22.2 & low & $<$1.04/no & 1, 8\\
   C/1989 X1 (Austin) & 89.3 & $\pi \times 5400^2$ & 18.0 & 25.6 & low & 1.07-1.20/weak &
   9, 10\\
   C/1989 Q1 (Okazaki- & 89.8 & $\pi \times 3630^2$ & 16.0 & 25.6 & low & 1.20/no
   & 11, 7\\
   Levy-Ludenko)\\
   D/1996 Q1 (Tabur) & 83.3 & 990$~\times~$990 & 25.4 & 24.7 & high & $\approx$1.05/weak & 12, 13\\
   & & 7422$~\times~$7422 & 15.9 & & low & &\\
   2P/Encke & 94.6 & $582 \times 582$ & $\ge$30 & 25.9 & high& 1.03/weak & 14, 15\\
   & & $\approx$3000$~\times~$4500 & 7.7 & & low \\
   \object{21P/Giacobini-Zinner} & 62.3 & 35~300~$\times$~35~300 & 15.7 & 17.6 & high &
   weak/weak &
   16, 17\\ \hline
   \end{tabular}}
\par
\smallskip
  {$^{1)}$ Observed phase angle.}\\
  {$^{2)}$ Observed degree of polarization.}\\
  {$^{3)}$ Polarization of a typical dusty comet at phase angle $\alpha_{\rm obs}$.}\\
   {$^{4)}$ References: (1) \citet{Chernova1993}; (2) \citet{Ney1982}; (3)
   \citet{Lynch1992}; (4) \citet{Rosenbush1997};}\\
   {~~~(5) \citet{Myers1984}; (6) \citet{Kikuchi1983};
   (7) \citet{Hanner1994}; (8) \citet{Hanner1985};}\\
   {~~~(9) \citet{Kikuchi1990}; (10) \citet{Hanner1993};
   (11) \citet{Rosenbush1994}; (12) \citet{Kiselev2001};}\\
   {~~~(13) \citet{Harker1999}; (14) This work; (15) \citet{Gehrz1989}; (16) \citet{Kiselev2000};}\\
   {~~~(17) \citet{Hanner1992}.}\\
\par
   \end{table}