deletions | additions       diff --git a/Now_its_time_time.tex b/Now_its_time_time.tex  index 61a3bab..9084312 100644  --- a/Now_its_time_time.tex  +++ b/Now_its_time_time.tex 
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star. {\color{blue}Ask your demonstrator how to extract the column   containing the pixel values, and transfer them across to the Excel on  a Windows PC.}  {\color{red} A perl script has been provided for you, which will extract this information. Run: {\color{red}Run  \begin{verbatim}  > ../extract_params.pl OUTPUT.FILE  \end{verbatim} 
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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_{10}(f) + c.  \end{equation}  Derive this form.}  For two sources, the difference in their magnitudes isthen  proportional to the ratio of their fluxes:  \begin{equation}  \Delta m = m_1 - m_2 = 2.5 \log_{10} \left(\frac{f_2}{f_1}\right) (f_2/f_1)  \label{eq:appmagfluxratio}  \end{equation}