I have a table with values. See the code:
\documentclass[paper = landscape, pagesize]{scrartcl}
\usepackage{siunitx}
\begin{document}
\setlength\tabcolsep{3pt}
\begin{tabular}{rSSSSSSSSSSS}
$k$ & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 & 11\\
$\frac{\vartheta}{\si{\celsius}}$ & 30 & 35 & 40 & 45 & 50 & 55 & 60 & 65 & 70 & 75 & 80\\
$\frac{U_{AB,m}(\vartheta)}{\si{\mV}}$ & 14,9 & 15,8 & 7,7 & 18,3 & 19 & 20 & 21,1 & 22,2 & 24,3 & 26,9 & 30,1\\
$\frac{R_{i}(\vartheta)}{\si{\ohm}}$ & 4,26162 & 3,29091 & 3,38843 & 2,0983 & 0,91519 & ,053 & -,70179 & -1,45605 & -1,13902 & -,28405 & 1,21793
\end{tabular}\\[\baselineskip]
Some text from Wikipedia\footnote{https://en.wikipedia.org/wiki/Entropy}: In statistical thermodynamics, entropy is a measure of the number of microscopic configurations that a thermodynamic system can have when in a state as specified by some macroscopic variables.\\[\baselineskip]
\begin{tabular}{rccccccccccc}
$k$ & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 & 10 & 11\\
$\frac{\vartheta}{\si{\celsius}}$ & 30 & 35 & 40 & 45 & 50 & 55 & 60 & 65 & 70 & 75 & 80\\
$\frac{U_{AB,m}(\vartheta)}{\si{\mV}}$ & 14,9 & 15,8 & 17,7 & 18,3 & 19 & 20 & 21,1 & 22,2 & 24,3 & 26,9 & 30,1\\
$\frac{R_{i}(\vartheta)}{\si{\ohm}}$ & 4,26162 & 3,29091 & 3,38843 & 2,0983 & 0,91519 & 0,053 & -0,70179 & -1,45605 & -1,13902 & -0,28405 & 1,21793
\end{tabular}
\end{document}
And the result:
But why is there so much space between the columns compared to for example a c-column. Even if I use very small space between the columns: \setlength\tabcolsep{3pt}.
Why it happens? How can I solve it?
Thank you for your help and effort in advance!

\sisetup{table-number-alignment=center}. The default is that thedecimal dotis centred, not the number, whence the large blank on the left of cells, due to the much larger number of digits in the decimal part. – Bernard Apr 10 '17 at 07:58Scolumns? The issue here is more that dissimilar numbers share a column, which would be addressed by transposing the table (along with the row/column counts swapping) – Chris H Apr 10 '17 at 09:06table-number-alignment=centeris implicitly set bytable-format– Joseph Wright Apr 10 '17 at 11:23center-decimal-comma? – Bernard Apr 10 '17 at 12:26