Non si riesce a centrare perché la tabella è troppo larga. Per questo supera il margine superiore della pagina. Ho provato a cambiare localmente i margini col pacchetto chngpage.
`\usepackage{chngpage}
`
Questo è il codice (ho eliminato alcune cose “strane”):
`\begin{landscape}
\footnotesize
\begin{adjustwidth}{}{-7em}
\begin{longtable}[l]{cccccccccccccccc}
\hline \\
(1) & (2) &(3) &(4) &(5) &(6) &(7) &(8) &(9) &(10) &(11) &(12) &(13) &(14) &(15) & (16) \\
N$\degree$ & RA & Dec & Err. & Count Rate & HR1 & HR2 & LM & U& B & V & I & Dist & $Log(F_{X}/F_{V})$ &ID& Note \\
&(h m s) & ($\degree$ $'$ $''$) & $('')$ & $(10^{-3} \text{s}^{-1})$& & & & & & & &$('')$& & & \\[1em]
\hline\\
1 & 00 52 05.72 & -72 26 04.1 & 1.23 & $219.41 \pm 4.29$ & -0.01$\pm$0.04 & -0.25$\pm$0.04 & 8809& 13.94$\pm$0.03 & 14.91$\pm$0.02 & 14.91$\pm$0.02 & 14.83$\pm$0.05 & 0.20 & -0.52$\pm$0.02 & HMXB & \\
2 & 00 53 23.97 & -72 27 14.8 & 1.23 & 155.36$\pm$3.45 & -0.10$\pm$0.04 & -0.24$\pm$0.05 & 6386& 15.06$\pm$0.03 & 16.11$\pm$0.02 & 16.19$\pm$0.12 & 16.14$\pm$0.24 & 0.65 & -0.19$\pm$0.05 & HMXB & \\
3 & 00 52 52.16 & -72 17 14.8 & 1.23 & 156.00$\pm$4.31 & -0.19$\pm$0.04 & -0.27$\pm$0.05 & 4085& 15.83$\pm$0.04 & 16.41$\pm$0.02 & 16.62$\pm$0.03 & 16.82$\pm$0.07 & 0.45 & 0.03$\pm$0.02 & HMXB & \\
4 & 00 55 35.25 & -72 29 06.9 & 1.23 & 201.51$\pm$5.77 & -0.02$\pm$0.05 & -0.05$\pm$0.06 & 3383& 13.60$\pm$0.03 & 14.65$\pm$0.02 & 14.69$\pm$0.03 & 14.67$\pm$0.04 & 0.75 & -0.58$\pm$0.02 & HMXB & \\
5 & 00 54 03.86 & -72 26 32.3 & 1.24 & 60.73$\pm$2.32 & 0.16$\pm$0.07 & -0.10$\pm$0.07 & 1625& 13.82$\pm$0.06 & 14.95$\pm$0.02 & 14.94$\pm$0.03 & 14.79$\pm$0.04 & 0.55 & -0.98$\pm$0.03 & HMXB & \\
6 & 00 54 31.46 & -72 18 11.6 & 1.25 & 73.16$\pm$3.27 & -0.45$\pm$0.07 & -0.26$\pm$0.14 & 1197& 15.61$\pm$0.03 & 16.48$\pm$0.04 & 16.57$\pm$0.03 & 16.81$\pm$0.04 & 2.61 & -0.51$\pm$0.04 & HMXB & \\
7 & 00 51 16.84 & -72 16 51.0 & 1.24 & 135.18$\pm$5.02 & -0.27$\pm$0.05 & -0.34$\pm$0.08 & 2059& 17.85$\pm$0.05 & 19.08$\pm$0.05 & 18.25$\pm$0.05 & 21.94$\pm$0.00 & 0.75 & 0.57$\pm$0.04 & Unknown & \\
8 & 00 54 56.18 & -72 26 47.3 & 1.25 & 49.35$\pm$2.45 & -0.12$\pm$0.09 & -0.22$\pm$0.12 & 840& 14.15$\pm$0.03 & 15.21$\pm$0.02 & 15.27$\pm$0.03 & 15.11$\pm$0.03 & 0.37 & -1.10$\pm$0.04 & HMXB & \\
9 & 00 53 31.63 & -72 22 40.7 & 1.27 & 30.81$\pm$1.67 & -0.48$\pm$0.08 & -0.23$\pm$0.15 & 642& 22.17$\pm$0.00 & 19.89$\pm$0.09 & 20.23$\pm$0.12 & 21.94$\pm$0.00 & 2.53 & 0.59$\pm$0.06 & Unknown & \\
\hline
\end{longtable}
\end{adjustwidth}
\end{landscape}
\clearpage`
In rosso ho evidenziato un esempio in base al quale dovresti uniformare le altre formule.
Antonio mi ha preceduto. Infatti mancano alcune informazioni. Bisogna caricare i pacchetti lscape,longtable,amsmath,gensymb,chngpage
Ciao e benvenuto/a nel forum
Ivan