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<section>
<h1 class="noindent">Photometric Systems Transformation Table</h1>
<p class="abstract">
Definition of a FITS table providing the transformation between
photometric systems.
</p>
<p>
The table is created by <samp>munipack phfotran</samp> action
and used by <samp>phcal</samp> action.
</p>
<p>
This specification has been developed for internal use in Munipack
and backward compatibility is not guarantied.
</p>
<h2>File Structure</h2>
<p>
The file has first HDU dummy without any machine-readable information
and just a short description and reference in comments.
</p>
<div class="table">
<table>
<caption>FITS file structure</caption>
<tr><th>HDU</th><th>EXTNAME</th><th>Description</th></tr>
<tr><td>0</td><td></td><td>Dummy<sup></sup></td></tr>
<tr><td>1</td><td>FOTRAN</td><td>The transformation table</td></tr>
</table>
</div>
<p>
The second HDU is a table with the transformation matrix.
EXTNAME is set to FOTRAN.
The header contains identifiers of input (instrumental) and output
(standard) photometry systems in keywords PHOTSYS1 and PHOTSYS2.
Amount of both columns and rows will generally variable and non-equal.
</p>
<div class="table">
<table>
<caption>FOTRAN extension keywords</caption>
<tr><th>Keyword</th><th>Value</th><th>Description</th></tr>
<tr><td>EXTNAME</td><td>FOTRAN</td><td>mandatory extension identifier</td></tr>
<tr><td>PHOTSYS1</td><td></td><td>instrumental photometry system</td></tr>
<tr><td>PHOTSYS2</td><td></td><td>standard photometry system</td></tr>
<tr><td>FILTER<i>i</i></td><td></td><td><i>i</i>-th standard filter</td></tr>
</table>
</div>
<p>
Columns of the table are named as instrumental filters. Rows
are equivalent filters. Lets elements of tables are <i>C<sub>i,j</sub></i>
than the values in the standard system (PHOTSYS2) are derived
from the instrumental system (PHOTSYS1) as
</p>
<p>
<p>
<i>
c'<sub>i</sub> = Σ<sub>j</sub> C<sub>ij</sub> c<sub>j</sub>
</i>
</p>
<p>
where <i>i,j = { B,V ...}</i> points on all available filters.
</p>
<div class="table">
<table>
<caption>Photometric System Transformation HDU Table</caption>
<tr><th>Column</th><th>Type</th><th>Description</th></tr>
<tr><td>FILTER</td><td>12A</td><td>Filter designation</td></tr>
<tr><td><i>C<sub>i1</sub></i></td><td>D</td><td>a coefficient</td></tr>
<tr><td><i>C<sub>i2</sub></i></td><td>D</td><td>a coefficient</td></tr>
<tr><td>..</td><td>D</td><td>a coefficient</td></tr>
<tr><td><i>C<sub>ij</sub></i></td><td>D</td><td>a coefficient</td></tr>
<tr><td>..</td><td>D</td><td>a coefficient</td></tr>
<tr><td><i>C<sub>iN</sub></i></td><td>D</td><td>a coefficient</td></tr>
</table>
</div>
<p>
The table can be created by hand, but the structure must be respected
and all identifiers included.
</p>
<h2>See Also</h2>
<p>
<a href="man_phfotran.html">Photometric System Transformation</a>,
<a href="man_phcal.html">Photometric Calibration</a>
</p>
</section>
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