deletions | additions       diff --git a/Now_its_time_time.tex b/Now_its_time_time.tex  index 9084312..6a95010 100644  --- a/Now_its_time_time.tex  +++ b/Now_its_time_time.tex 
...
f = 2.51^{-m + c}  \label{eq:fluxcalib}  \end{equation}  where $c$ is a constant which we're going to determine. {\color{red}In practice, this equation is usually rearranged to give:   \begin{equation} m = -2.5\log(f) -2.5\log_{10}(f) + c. \end{equation}   Derive this form.}  For two sources, the difference in their magnitudes is proportional to the  ratio of their fluxes: