\begin{table}%t1
%\centering
\par
\caption{General characteristics of the observational material.
The succesive columns signify: comet designation and name (Col.~1)
perihelion time, $T$, and perihelion distance, $q$
(2), observational arc and number of all observations (3), {rms} for the pure gravitational orbital fitting to pre-periherlion
(4), post-perihelion (5) and all (6) observations, {rms} for
the NG~orbital fitting to all observations (7), original (8) and
future (9) reciprocals of semimajor axes in units of $10^{-6}$~AU$^{-1}$. \label{tab1}}
 { 
\begin{tabular}{ccccccccc} \hline\hline
 Comet      & Perihelion   &  Observational        & \multicolumn{4}{c}{{rms}}                & $(1/a)_{\rm{ori}}$ & $(1/a)_{\rm{fut}}$        \\
 name       & time $T$ [Date]&material             & \multicolumn{3}{c}{Pure grav. case}                & NG case   & \multicolumn{2}{c}{ NG }     \\
            & $q$ [AU]     & (Number of obs.)      & pre-         & post-     & all                    & all              & \multicolumn{2}{c}{ (pure grav.  )} \\
            &              &                       & perih.       &    perih. &                        &                  &            &                        \\
            \hline
&&&&&&&&  \\
1996 B2     & 1996 05 01   &  19960101--19961102 & 1\farcs 02 & 1\farcs 19 & 1\farcs 66         & 1\farcs 08 &   1515        &  554          \\
Hyakutake   & 0.230        &        (1026)         & (971)      & (55)       &                    &            &  (1400)       & (540)         \\
&&&&&&&&  \\
1959 Y1     & 1960 03 21   &  19600104--19600617 & 1\farcs 29 & 2\farcs 14 & 3\farcs 00         & 1\farcs 64 & $-$202        & $-$319        \\
Burnham     & 0.504        &        (88)           & (34)       & (54)       &                    &            &  ($-$139)     & ($-$582)      \\
&&&&&&&&  \\
1969 Y1     & 1970 03 20   &  19691230--19701027 & 0\farcs 80 & 1\farcs 68 & 2\farcs 00         & 1\farcs 53 &   7381        &  7126         \\
Bennett     & 0.538        &        (548)          & (159)      & (389)      &                    &            &  (7317)       & (7126)        \\
&&&&&&&&  \\
1999 H1     & 1999 07 11   &  19990416--20000108 & 0\farcs 71 & 0\farcs 69 & 0\farcs 98         & 0\farcs 69 &  1288         &   397         \\
Lee         & 0.708        &        (1032)         & (352)      & (680)      &                    &            & (1313)        &  (365)        \\
&&&&&&&&  \\
1991 T2     & 1992 07 24   &  19911006--19920821 & 1\farcs 21 & --         & 1\farcs 21         & 1\farcs 14 &   894         &  1019         \\
Shoemaker--Levy& 0.836      &        (212)          & (209)      & (3)        &                    &            & ( 941)        & ( 434)        \\
&&&&&&&&  \\
1993 Y1     & 1994 03 31   &  19931217--19940908 & 0\farcs 82 & 1\farcs 12 & 1\farcs 23         & 1\farcs 00 &  7349         &  8442         \\
McNaught--Russell    & 0.868    &        (397)          & (146)      & (251)      &                    &            & (7171)        & (8261)        \\
&&&&&&&&  \\
1995 O1     & 1997 04 01   &  19930427--20011217 & 1\farcs 06 & 1\farcs 06 & 1\farcs 29         & 1\farcs 07 &  3841         &  5588         \\
Hale-Bopp   & 0.918        &        (3550)         & (2580)     & (970)      &                    &            & (3797)        & (5566)        \\
&&&&&&&&  \\
1990 K1     & 1990 10 25   &  19900521--19920401 & 1\farcs 18 & 1\farcs 22 & 1\farcs 94         & 1\farcs 21 &   26          &  $-$790       \\
Levy        & 0.939        &        (678)          & (590)      & (88)       &                    &            & (112)         & ($-$849)      \\
&&&&&&&&  \\
1999 J3     & 1999 09 20   &  19990512--20000228 & 0\farcs 66 & 1\farcs 12 & 1\farcs 25         & 0\farcs 83 &  1150         &   963         \\
Linear      & 0.977        &        (196)          & (91)       & (105)      &                    &            & (1084)        &  (769)        \\
&&&&&&&&  \\
1995 Y1     & 1996 02 24   &  19951226--19960921 & 0\farcs 79 & 0\farcs 72 & 0\farcs 96         & 0\farcs 80 &  $-$67        &   649         \\
Hyakutake   & 1.055        &        (262)          & (185)      & (77)       &                    &            & ($-$4)        & (1119)        \\
&&&&&&&&  \\
1998 P1     & 1998 10 17   &  19980811--19990515 & 0\farcs 58 & 1\farcs 73 & 4\farcs 58         & 1\farcs 10 &  ~~211        &  1320         \\
Williams    & 1.147        &        (461)          & (133)      & (328)      &                    &            & ($-$125)      & (1119)        \\
&&&&&&&&  \\
1999 T1     & 2000 12 13   &  19991007--20011202 & 0\farcs 82 & 0\farcs 45 & 1\farcs 27         & 0\farcs 76 &   1111        &   141         \\
McNaught--Hartley    & 1.172    &        (481)          & (260)      & (442)      &                    &            & ( 1111)       & ( 34)         \\
&&&&&&&&  \\
1986 P1A    & 1987 04 21   &  19860805--19890411 & 1\farcs 31 & 1\farcs 32 & 1\farcs 62         & 1\farcs 31 &   42          &   768         \\
Wilson      & 1.200        &        (688)          & (507)      & (181)      &                    &            & ($-$0.4)      &  (725)        \\
&&&&&&&&  \\
1996 E1     & 1996 07 27   &  19960315--19961012 & 0\farcs 80 & 0\farcs 75 & 1\farcs 01         & 0\farcs 77 &   28          &    34         \\
NEAT        & 1.359        &        (249)          & (177)      & (72)       &                    &            & ($-$43)       &   (36)        \\
&&&&&&&&  \\
1998 T1     & 1999 06 25   &  19981002--20000508 & 0\farcs 59 & 0\farcs 77 & 1\farcs 43         & 0\farcs 70 &  560          &  1481         \\
Linear      & 1.468        &        (466)          & (263)      & (203)      &                    &            & (559)         & (1458)        \\
&&&&&&&&  \\
1975 T1     & 1975 12 25   &  19751006--19761024 & 1\farcs 35 & 1\farcs 21 & 1\farcs 48         & 1\farcs 31 &  2052         &  1572         \\
Mori-Sato--Fujikawa    & 1.604  &        (197)          & (139)      & (58)       &                    &            & (1958)   & (1540)        \\
&&&&&&&&  \\
1987 W2     & 1988 03 03   &  19871121--19880812 & 0\farcs 93 & 1\farcs 56 & 1\farcs 18         & 1\farcs 06 &  401          &    50         \\
Furuyama    & 1.680        &        (154)          & (144)      & (10)       &                    &            & (266)         & (   7)        \\
&&&&&&&&  \\
1993 A1     & 1994 01 13   &  19921126--19940817 & 1\farcs 33 & 0\farcs 66 & 2\farcs 79         & 1\farcs 14 &   58          &  $-$409         \\
Mueller     & 1.938        &        (746)          & (671)      & (75)       &                    &            & ($-$19)       & ($-$539)        \\
&&&&&&&&  \\
1991 B1     & 1991 12 31   &  19910113--19930815 & 0\farcs 96 & 0\farcs 92 & 1\farcs 06         & 0\farcs 93 &  3027         &  3100         \\
Shoemaker--Levy    & 2.264      &        (429)          & (123)      & (306)      &                    &            & (3019)        & (3083)        \\
\hline
\end{tabular}
}
\end{table}