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<H3><A NAME="SECTION003042700000000000000">
Flux Calibration</A>
</H3>
<P>
The Flux Calibration window contains the options required for the
atmospheric extinction and flux calibration.
Click the
<!-- MATH: $\fbox{\tt Flux...}$ -->
<IMG
WIDTH="94" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1109.gif"
ALT="\fbox{\tt Flux...}">
button in the Main window to
pop up the Flux Calibration window.
<P>
The
<!-- MATH: $\fbox{\tt Extinct}$ -->
<IMG
WIDTH="94" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1110.gif"
ALT="\fbox{\tt Extinct}">
button corrects the spectra for extinction and
requires that the field <B>Extinction table:</B> contains a valid
extinction table name. After clicking
<!-- MATH: $\fbox{\tt Extinct}$ -->
<IMG
WIDTH="94" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1111.gif"
ALT="\fbox{\tt Extinct}">
a
selection list for <B>.bdf</B> files
pops up. Click the file you want to correct. A small prompt window
asks for the airmass. If the airmass appears in the file header,
that value is used as default. The output is stored by default
in a file with the original name plus the suffix _<TT>ext</TT>.
Airmass and output file name can be modified before clicking on
<!-- MATH: $\fbox{\tt OK}$ -->
<IMG
WIDTH="37" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1112.gif"
ALT="\fbox{\tt OK}">
which activates the command <TT>EXTINCTION/LONG</TT>.
<P>
The
<!-- MATH: $\fbox{\tt Integr}$ -->
<IMG
WIDTH="83" HEIGHT="32" ALIGN="BOTTOM" BORDER="0"
SRC="img1113.gif"
ALT="\fbox{\tt Integr}">
button allows the response table to be generated.
The field <B>Flux table:</B> must be updated with the name of the standard
star flux table. This table can be plotted by clicking on the button
<!-- MATH: $\fbox{\tt Plot Flux}$ -->
<IMG
WIDTH="117" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1114.gif"
ALT="\fbox{\tt Plot Flux}">.
After clicking
<!-- MATH: $\fbox{\tt Integr}$ -->
<IMG
WIDTH="83" HEIGHT="32" ALIGN="BOTTOM" BORDER="0"
SRC="img1115.gif"
ALT="\fbox{\tt Integr}">
a file selection window appears
requesting the name of the standard star image, which must
be a one dimensional reduced, extinction corrected
spectrum. Click the name. The name of the resulting intermediate
response table is stored in the MIDAS keyword <TT>RESPTAB</TT> and
by default set to <B>resp.tbl</B>. Values of this table can be
interactively edited by clicking on
<!-- MATH: $\fbox{\tt Edit}$ -->
<IMG
WIDTH="60" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1116.gif"
ALT="\fbox{\tt Edit}">.
<P>
<BR>
<DIV ALIGN="CENTER"><A NAME="fig:xflux"> </A><A NAME="28039"> </A>
<TABLE WIDTH="50%">
<CAPTION><STRONG>Figure G.8:</STRONG>
Flux Calibration window</CAPTION>
<TR><TD></TD></TR>
</TABLE>
</DIV>
<BR>
<P>
The response table must be interpolated to generate the final response
curve, which name is provided in the field <B>Response curve:</B>.
The Section <B>FITTING PARAMETERS</B> allows the different values
and options to be selected (See Section <A HREF="node519.html#flux-cal">G.3.8</A> and Chapter 6
Vol. B). The button
<!-- MATH: $\fbox{\tt Fitting space}$ -->
<IMG
WIDTH="163" HEIGHT="32" ALIGN="BOTTOM" BORDER="0"
SRC="img1118.gif"
ALT="\fbox{\tt Fitting space}">
radio button allows the calibration curves
to be plotted in two different ways. The first option
<!-- MATH: $\fbox{\tt ratio/wave}$ -->
<IMG
WIDTH="128" HEIGHT="31" ALIGN="BOTTOM" BORDER="0"
SRC="img1119.gif"
ALT="\fbox{\tt ratio/wave}">
is the standard plane used by MIDAS. The second option
<!-- MATH: $\fbox{\tt
magnitude/wave}$ -->
<IMG
WIDTH="175" HEIGHT="34" ALIGN="BOTTOM" BORDER="0"
SRC="img1120.gif"
ALT="\fbox{\tt
magnitude/wave}">
plots <IMG
WIDTH="42" HEIGHT="22" ALIGN="BOTTOM" BORDER="0"
SRC="img1121.gif"
ALT="$\Delta m$"> versus <IMG
WIDTH="19" HEIGHT="22" ALIGN="BOTTOM" BORDER="0"
SRC="img1122.gif"
ALT="$\lambda$">
and generally has
the advantage to require lower order curves to fit the response.
The
<!-- MATH: $\fbox{\tt Fitting type}$ -->
<IMG
WIDTH="151" HEIGHT="32" ALIGN="BOTTOM" BORDER="0"
SRC="img1123.gif"
ALT="\fbox{\tt Fitting type}">
button allows fitting the
curves with either polynomials or splines.
<P>
Clicking on
<!-- MATH: $\fbox{\tt Fit}$ -->
<IMG
WIDTH="48" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1124.gif"
ALT="\fbox{\tt Fit}">
activates the MIDAS command
<TT>RESPONSE/LONG</TT>.
The response curve can also be generated by filtering
with the button
<!-- MATH: $\fbox{\tt Filter}$ -->
<IMG
WIDTH="83" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1125.gif"
ALT="\fbox{\tt Filter}">.
The response curve can be plotted by
clicking on the button
<!-- MATH: $\fbox{\tt Plot resp}$ -->
<IMG
WIDTH="117" HEIGHT="32" ALIGN="BOTTOM" BORDER="0"
SRC="img1126.gif"
ALT="\fbox{\tt Plot resp}">.
<P>
Reduced, extinction corrected spectra can be corrected for the
instrumental response with the button
<!-- MATH: $\fbox{\tt Correct}$ -->
<IMG
WIDTH="94" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1127.gif"
ALT="\fbox{\tt Correct}">.
Clicking on this button pops up a file selection list.
Click the name of the spectrum. A small prompt window appears
requesting the name of the output file. The
default is the input file name with the suffix _<TT>cor</TT>.
Clicking on
<!-- MATH: $\fbox{\tt OK}$ -->
<IMG
WIDTH="37" HEIGHT="27" ALIGN="BOTTOM" BORDER="0"
SRC="img1128.gif"
ALT="\fbox{\tt OK}">
sends a command <TT>CALIBRATE/FLUX</TT> to the
MIDAS monitor.
<P>
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-15</I>
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