Vertical spacing of captions in booktabs

Question

Both \abovetopsep and \belowbottomsep are 0.0pt. But for some reason there's extra space between the bottom rule and "my second caption" in the table below.

Q: What is that space? Where does it come from?

Ultimately, I'd like to do the following:

\setlength{\abovetopsep}{<the width between the bottom rule and "my second caption">}

so that there's some uniformity in the vertical placement of captions above and below tabulars.

Q: Is there another, maybe more standard, method for doing this?

\documentclass{article}
\usepackage{booktabs}
\begin{document}
\begin{table}
  \centering
  \caption{my first caption}
  \begin{tabular}{ll}
    \toprule
    foo & bar \\
    \midrule
    baz & bog \\
    \bottomrule 
  \end{tabular}
  \caption{my second caption}
\end{table}
\end{document} 

Answer 1

Ad 1: As egreg has commented, booktabs has nothing to do with captions. The standard document classes article, book, and report define the lengths \abovecaptionskip (default value: 10pt) and \belowcaptionskip (default value: 0pt). \abovecaptionskip is responsible for the space in your example.

Ad 2 : Have a look at the caption package, especially at section 2.6 "Skips" of its manual.