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<div class="section" id="what-s-new-in-astropy-0-2">
<span id="whatsnew-0-2"></span><h1>What’s New in Astropy 0.2<a class="headerlink" href="#what-s-new-in-astropy-0-2" title="Permalink to this headline">¶</a></h1>
<div class="section" id="ascii-table-i-o">
<h2>ASCII table I/O<a class="headerlink" href="#ascii-table-i-o" title="Permalink to this headline">¶</a></h2>
<p>The <a class="reference internal" href="../io/ascii/index.html#io-ascii"><em>astropy.io.ascii</em></a> subpackage allows reading and writing of
table data in ASCII format. A number of improvements have been made to this
package, some of which break compatibility with the original <a class="reference external" href="https://asciitable.readthedocs.org/">asciitable</a> package.</p>
<p>The biggest change is full integration with the <a class="reference internal" href="../table/index.html#astropy-table"><em>Table</em></a> class
so that table and column metadata (e.g. keywords, units, description,
formatting) are directly available in the output table object. The CDS,
DAOphot, and IPAC format readers now provide this type of integrated metadata.
Missing value support is now provided using <a class="reference internal" href="../table/index.html#astropy-table"><em>masked tables</em></a>
instead of NumPy masked arrays.</p>
<p>There is an important change in way that input data are parsed in the
<a class="reference internal" href="../_generated/astropy.io.ascii.ui.write.html#astropy.io.ascii.ui.write" title="astropy.io.ascii.ui.write"><tt class="xref py py-func docutils literal"><span class="pre">write()</span></tt></a> function. In version 0.1 of <tt class="xref py py-obj docutils literal"><span class="pre">astropy</span></tt>, a
list of lists was interpreted to be a <em>list of data rows</em>, corresponding to the
behavior in <a class="reference external" href="https://asciitable.readthedocs.org/">asciitable</a>. Starting from
version 0.2, a list of lists is interpreted as a <em>list of data columns</em>. This corresponds
to the behavior of the <a class="reference internal" href="../_generated/astropy.table.table.Table.html#astropy.table.table.Table" title="astropy.table.table.Table"><tt class="xref py py-class docutils literal"><span class="pre">Table</span></tt></a> class.</p>
<p>Finally, a reader class to read SExtractor table outputs is now available.</p>
</div>
<div class="section" id="coordinates">
<h2>Coordinates<a class="headerlink" href="#coordinates" title="Permalink to this headline">¶</a></h2>
<p>The <a class="reference internal" href="../coordinates/index.html#astropy-coordinates"><em>astropy.coordinates</em></a> subpackage was added in Astropy 0.2, and
adds a framework for defining celestial and other astronomical coordinate
systems, as well as transformations between them. A few simple usage examples
include:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">astropy.coordinates</span> <span class="kn">as</span> <span class="nn">coord</span>
<span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">coord</span><span class="o">.</span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="n">ra</span><span class="o">=</span><span class="mf">10.68458</span><span class="p">,</span> <span class="n">dec</span><span class="o">=</span><span class="mf">41.26917</span><span class="p">,</span> <span class="n">unit</span><span class="o">=</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">degree</span><span class="p">))</span>
<span class="gp">>>> </span><span class="n">c</span><span class="o">.</span><span class="n">ra</span>
<span class="go"><RA 10.68458 deg></span>
<span class="gp">>>> </span><span class="n">c</span><span class="o">.</span><span class="n">galactic</span>
<span class="go"><GalacticCoordinates l=121.17430 deg, b=-21.57280 deg></span>
</pre></div>
</div>
<p>Currently a limited set of standard coordinate systems are included, but more will be
added in the next release. There is also an
<a class="reference internal" href="../coordinates/sgr-example.html#sgr-example"><em>example of creating a custom coordinate system</em></a> in the documentation.</p>
<p>The package also includes a representation of angles (<a class="reference internal" href="../_generated/astropy.coordinates.angles.Angle.html#astropy.coordinates.angles.Angle" title="astropy.coordinates.angles.Angle"><tt class="xref py py-class docutils literal"><span class="pre">Angle</span></tt></a>)
that may be useful in other contexts. It also supports distances in
celestial coordinates, which allows a complete mapping to 3D coordinates:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">coord</span><span class="o">.</span><span class="n">ICRSCoordinates</span><span class="p">(</span><span class="s">'00h42m44.3s +41d16m9s'</span><span class="p">,</span> <span class="n">distance</span><span class="o">=</span><span class="n">Distance</span><span class="p">(</span><span class="mi">770</span><span class="p">,</span> <span class="n">u</span><span class="o">.</span><span class="n">kpc</span><span class="p">))</span>
<span class="gp">>>> </span><span class="n">c</span><span class="o">.</span><span class="n">cartesian</span>
<span class="go"><CartesianPoints (568.712888217, 107.300935969, 507.889909249) kpc></span>
</pre></div>
</div>
<p>The package also supports a simple interface for retrieving coordinates for an object by
name using the <a class="reference external" href="http://cds.u-strasbg.fr/cgi-bin/Sesame">Sesame Name Resolver</a> . This works
on all subclasses of <a class="reference internal" href="../_generated/astropy.coordinates.coordsystems.SphericalCoordinatesBase.html#astropy.coordinates.coordsystems.SphericalCoordinatesBase" title="astropy.coordinates.coordsystems.SphericalCoordinatesBase"><tt class="xref py py-class docutils literal"><span class="pre">SphericalCoordinatesBase</span></tt></a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">coord</span><span class="o">.</span><span class="n">ICRSCoordinates</span><span class="o">.</span><span class="n">from_name</span><span class="p">(</span><span class="s">"M42"</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">c</span><span class="o">.</span><span class="n">ra</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">dec</span>
<span class="go">(<RA 83.82208 deg>, <Dec -5.39111 deg>)</span>
<span class="gp">>>> </span><span class="n">c</span> <span class="o">=</span> <span class="n">coord</span><span class="o">.</span><span class="n">GalacticCoordinates</span><span class="o">.</span><span class="n">from_name</span><span class="p">(</span><span class="s">"M42"</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">c</span><span class="o">.</span><span class="n">l</span><span class="p">,</span> <span class="n">c</span><span class="o">.</span><span class="n">b</span>
<span class="go">(<Angle -150.98622 deg>, <Angle -19.38162 deg>)</span>
</pre></div>
</div>
<p>For more details about this feature, see
<a class="reference internal" href="../_generated/astropy.coordinates.name_resolve.get_icrs_coordinates.html#astropy.coordinates.name_resolve.get_icrs_coordinates" title="astropy.coordinates.name_resolve.get_icrs_coordinates"><tt class="xref py py-func docutils literal"><span class="pre">get_icrs_coordinates()</span></tt></a> and
<a class="reference internal" href="../_generated/astropy.coordinates.coordsystems.SphericalCoordinatesBase.html#astropy.coordinates.coordsystems.SphericalCoordinatesBase.from_name" title="astropy.coordinates.coordsystems.SphericalCoordinatesBase.from_name"><tt class="xref py py-meth docutils literal"><span class="pre">from_name()</span></tt></a>.</p>
<p>Note that this subpackage is still under heavy development, and likely will
undergo significant changes in the next few versions.</p>
</div>
<div class="section" id="cosmology">
<h2>Cosmology<a class="headerlink" href="#cosmology" title="Permalink to this headline">¶</a></h2>
<p>There have been several improvements to <a class="reference internal" href="../cosmology/index.html#astropy-cosmology"><em>astropy.cosmology</em></a> subpackage, some of which required minor API
changes. Contributions to the energy density from photons and
neutrinos are now taken into account, and so cosmological quantities
should be accurate all the way up to z ~ 1100, corresponding to the
CMB surface of last scattering. There are also new classes to
represent flat cosmologies, optionally with a time-varying dark energy
parameter <tt class="docutils literal"><span class="pre">w</span></tt> using the popular parameterisations by <a class="reference external" href="http://adsabs.harvard.edu/abs/2003PhRvL..90i1301L">Linder 2003</a>.</p>
<p>There are two API changes:</p>
<blockquote>
<div><ul class="simple">
<li>Previously the <tt class="docutils literal"><span class="pre">Om</span></tt>, <tt class="docutils literal"><span class="pre">Ol</span></tt> and <tt class="docutils literal"><span class="pre">Ok</span></tt> attributes of a
<tt class="xref py py-obj docutils literal"><span class="pre">Cosmology</span></tt> class referred to densities at z = 0. These have been
renamed to <tt class="docutils literal"><span class="pre">Om0</span></tt>, <tt class="docutils literal"><span class="pre">Ol0</span></tt>, and <tt class="docutils literal"><span class="pre">Ok0</span></tt>. <tt class="docutils literal"><span class="pre">Om</span></tt>, <tt class="docutils literal"><span class="pre">Ol</span></tt> and
<tt class="docutils literal"><span class="pre">Ok</span></tt> are now methods that give the relevant density as a
function of redshift. This change makes their behaviour consistent
with that of the Hubble parameter attribute and method (<tt class="docutils literal"><span class="pre">H0</span></tt> and
<tt class="docutils literal"><span class="pre">H</span></tt>).</li>
<li>The <tt class="xref py py-obj docutils literal"><span class="pre">FLRWCosmology</span></tt> class has been renamed to
<a class="reference internal" href="../_generated/astropy.cosmology.core.FLRW.html#astropy.cosmology.core.FLRW" title="astropy.cosmology.core.FLRW"><tt class="xref py py-class docutils literal"><span class="pre">FLRW</span></tt></a>.</li>
</ul>
</div></blockquote>
<p>So while in version 0.1 you could define a flat cosmology in following way:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">astropy.cosmology</span> <span class="kn">import</span> <span class="n">FLRWCosmology</span>
<span class="gp">>>> </span><span class="n">cosmo</span> <span class="o">=</span> <span class="n">FLRWCosmology</span><span class="p">(</span><span class="n">H0</span><span class="o">=</span><span class="mi">70</span><span class="p">,</span> <span class="n">Om</span><span class="o">=</span><span class="mf">0.3</span><span class="p">,</span> <span class="n">Ol</span><span class="o">=</span><span class="mf">0.7</span><span class="p">)</span>
</pre></div>
</div>
<p>Now you would do the same thing using:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">astropy.cosmology</span> <span class="kn">import</span> <span class="n">FlatLambdaCDM</span>
<span class="gp">>>> </span><span class="n">cosmo</span> <span class="o">=</span> <span class="n">FlatLambdaCDM</span><span class="p">(</span><span class="n">H0</span><span class="o">=</span><span class="mi">70</span><span class="p">,</span> <span class="n">Om0</span><span class="o">=</span><span class="mf">0.3</span><span class="p">)</span>
</pre></div>
</div>
<p>The convenience functions
<a class="reference internal" href="../_generated/astropy.cosmology.funcs.kpc_proper_per_arcmin.html#astropy.cosmology.funcs.kpc_proper_per_arcmin" title="astropy.cosmology.funcs.kpc_proper_per_arcmin"><tt class="xref py py-func docutils literal"><span class="pre">kpc_proper_per_arcmin()</span></tt></a>,
<a class="reference internal" href="../_generated/astropy.cosmology.funcs.kpc_comoving_per_arcmin.html#astropy.cosmology.funcs.kpc_comoving_per_arcmin" title="astropy.cosmology.funcs.kpc_comoving_per_arcmin"><tt class="xref py py-func docutils literal"><span class="pre">kpc_comoving_per_arcmin()</span></tt></a>,
<a class="reference internal" href="../_generated/astropy.cosmology.funcs.arcsec_per_kpc_proper.html#astropy.cosmology.funcs.arcsec_per_kpc_proper" title="astropy.cosmology.funcs.arcsec_per_kpc_proper"><tt class="xref py py-func docutils literal"><span class="pre">arcsec_per_kpc_proper()</span></tt></a> and
<a class="reference internal" href="../_generated/astropy.cosmology.funcs.arcsec_per_kpc_comoving.html#astropy.cosmology.funcs.arcsec_per_kpc_comoving" title="astropy.cosmology.funcs.arcsec_per_kpc_comoving"><tt class="xref py py-func docutils literal"><span class="pre">arcsec_per_kpc_comoving()</span></tt></a> are now all
available as methods of the <tt class="xref py py-class docutils literal"><span class="pre">Cosmology</span></tt>
object.</p>
<p>Finally, a new set of cosmological parameters from the 9 year WMAP
results (<tt class="xref py py-obj docutils literal"><span class="pre">astropy.cosmology.WMAP9</span></tt>) has been added from the recently
submitted paper by <a class="reference external" href="http://arxiv.org/abs/1212.5226">Hinshaw et
al.</a>. Since this paper has not yet
been refereed, convenience functions still use the 7 year WMAP results
if you don’t explicitly specify a cosmology.</p>
</div>
<div class="section" id="data-tables">
<h2>Data Tables<a class="headerlink" href="#data-tables" title="Permalink to this headline">¶</a></h2>
<p>The <a class="reference internal" href="../table/index.html#astropy-table"><em>astropy.table</em></a> subpackage was first introduced for
preview in Astropy 0.1 and provides functionality for storing and manipulating
heterogenous tables of data in a way that is familiar to numpy users. Some key
features include:</p>
<ul class="simple">
<li>Modify a table by adding or removing columns, changing column names,
or adding new rows of data.</li>
<li>Include table and column metadata as flexible data structures.</li>
<li>Specify a description, units and output formatting for columns.</li>
<li>Interactively scroll through long tables similar to using <tt class="docutils literal"><span class="pre">more</span></tt>.</li>
</ul>
<p>Astropy 0.2 brings the addition of integrated support for missing values via
the Numpy <a class="reference external" href="http://docs.scipy.org/doc/numpy/reference/maskedarray.html">masked array</a> class. This
feature requires Numpy version 1.5 or greater because of issues
with masked arrays in previous versions.</p>
<p>The <a class="reference internal" href="../_generated/astropy.table.table.Table.html#astropy.table.table.Table" title="astropy.table.table.Table"><tt class="xref py py-class docutils literal"><span class="pre">Table</span></tt></a> class now connects to the new <a class="reference internal" href="#i-o-framework">I/O
framework</a> read and write methods. For example, assume you have a table
of magnitudes called <tt class="docutils literal"><span class="pre">mags</span></tt> with columns <tt class="docutils literal"><span class="pre">B</span></tt> and <tt class="docutils literal"><span class="pre">V</span></tt>. You can add a new
column <tt class="docutils literal"><span class="pre">B-V</span></tt> and write out to an ASCII table with:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">BV</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">data</span><span class="o">=</span><span class="n">mags</span><span class="p">[</span><span class="s">'B'</span><span class="p">]</span> <span class="o">-</span> <span class="n">mags</span><span class="p">[</span><span class="s">'V'</span><span class="p">],</span> <span class="n">name</span><span class="o">=</span><span class="s">'B-V'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">mags</span><span class="o">.</span><span class="n">add_column</span><span class="p">(</span><span class="n">BV</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">mags</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s">'mags_BV.dat'</span><span class="p">,</span> <span class="n">format</span><span class="o">=</span><span class="s">'ascii'</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="section" id="i-o-framework">
<h2>I/O framework<a class="headerlink" href="#i-o-framework" title="Permalink to this headline">¶</a></h2>
<p>This version sees the introduction of a framework that makes it easy to read
in or write out data objects. This can be used for
<a class="reference internal" href="../_generated/astropy.table.table.Table.html#astropy.table.table.Table" title="astropy.table.table.Table"><tt class="xref py py-class docutils literal"><span class="pre">Table</span></tt></a> and <a class="reference internal" href="../_generated/astropy.nddata.nddata.NDData.html#astropy.nddata.nddata.NDData" title="astropy.nddata.nddata.NDData"><tt class="xref py py-class docutils literal"><span class="pre">NDData</span></tt></a>
objects, by doing e.g.:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">astropy.table</span> <span class="kn">import</span> <span class="n">Table</span>
<span class="gp">>>> </span><span class="n">t</span> <span class="o">=</span> <span class="n">Table</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="s">'my_table.xml'</span><span class="p">,</span> <span class="n">format</span><span class="o">=</span><span class="s">'vo'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">t</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s">'my_table.hdf5'</span><span class="p">)</span>
</pre></div>
</div>
<p>At this time, this framework supports ASCII tables, HDF5 tables, and VO
tables, and will be extended to support FITS tables and datasets in the next
version. Users can also register their own file formats directly, in case
these are not present in Astropy. More information about how to read/write
<a class="reference internal" href="../_generated/astropy.table.table.Table.html#astropy.table.table.Table" title="astropy.table.table.Table"><tt class="xref py py-class docutils literal"><span class="pre">Table</span></tt></a> objects using the built-in formats is
available in <a class="reference internal" href="../io/unified.html#table-io"><em>Unified file read/write interface</em></a>, and more information about the I/O framework and
how to register new file formats can be found in <a class="reference internal" href="../io/registry.html#io-registry"><em>I/O Registry (astropy.io.registry)</em></a>.</p>
</div>
<div class="section" id="time">
<h2>Time<a class="headerlink" href="#time" title="Permalink to this headline">¶</a></h2>
<p>The <a class="reference internal" href="../time/index.html#astropy-time"><em>astropy.time</em></a> package is new in Astropy 0.2 and
provides functionality for manipulating times and dates. Specific emphasis is
placed on supporting time scales (e.g. UTC, TAI, UT1) and time representations
(e.g. JD, MJD, ISO 8601) that are used in astronomy. The underlying
computations are mostly done with the C language <a class="reference external" href="http://www.iausofa.org/index.html">SOFA</a> time and calendar
routines. A simple example follows:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">astropy.time</span> <span class="kn">import</span> <span class="n">Time</span>
<span class="gp">>>> </span><span class="n">times</span> <span class="o">=</span> <span class="p">[</span><span class="s">'1999-01-01 00:00:00.123456789'</span><span class="p">,</span> <span class="s">'2010-01-01 00:00:00'</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">t</span> <span class="o">=</span> <span class="n">Time</span><span class="p">(</span><span class="n">times</span><span class="p">,</span> <span class="n">format</span><span class="o">=</span><span class="s">'iso'</span><span class="p">,</span> <span class="n">scale</span><span class="o">=</span><span class="s">'utc'</span><span class="p">)</span>
</pre></div>
</div>
<p>The <tt class="docutils literal"><span class="pre">format</span></tt> argument specifies how to interpret <a class="reference internal" href="../time/index.html#time-format"><em>Time Format</em></a> of the
input values, e.g. ISO or JD or Unix time. The <tt class="docutils literal"><span class="pre">scale</span></tt> argument specifies
the <a class="reference internal" href="../time/index.html#time-scale"><em>Time Scale</em></a> for the values, e.g. UTC or TT or UT1. Converting to
another time <tt class="docutils literal"><span class="pre">format</span></tt> or time <tt class="docutils literal"><span class="pre">scale</span></tt> is a snap:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">t</span><span class="o">.</span><span class="n">jd</span> <span class="c"># Get an array of JD times</span>
<span class="go">array([ 2451179.50000143, 2455197.5 ])</span>
<span class="gp">>>> </span><span class="n">t</span><span class="o">.</span><span class="n">tt</span> <span class="c"># Get a new Time object with values in the TT time scale</span>
<span class="go"><Time object: scale='tt' format='iso' vals=['1999-01-01 00:01:04.307' '2010-01-01 00:01:06.184']></span>
</pre></div>
</div>
</div>
<div class="section" id="units-and-quantities">
<h2>Units and quantities<a class="headerlink" href="#units-and-quantities" title="Permalink to this headline">¶</a></h2>
<p><a class="reference internal" href="../units/index.html#astropy-units"><em>Units (astropy.units)</em></a> handles defining and converting between physical
units, and performing arithmetic with physical quantities (numbers
with associated units).</p>
<p>Units can be converted to one another:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">astropy</span> <span class="kn">import</span> <span class="n">units</span> <span class="k">as</span> <span class="n">u</span>
<span class="gp">>>> </span><span class="c"># Convert from parsec to meter</span>
<span class="gp">>>> </span><span class="n">u</span><span class="o">.</span><span class="n">pc</span><span class="o">.</span><span class="n">to</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">m</span><span class="p">)</span>
<span class="go">3.0856776e+16</span>
</pre></div>
</div>
<p>It also handles equivalencies that hold true in certain contexts, such
as that between wavelength and frequency:</p>
<div class="highlight-python"><pre># Wavelength to frequency doesn't normally work
>>> u.nm.to(u.Hz, [1000, 2000])
UnitsException: 'nm' (length) and 'Hz' (frequency) are not convertible
# ...but by passing an equivalency unit (spectral()), it does...
>>> u.nm.to(u.Hz, [1000, 2000], equivalencies=u.spectral())
array([ 2.99792458e+14, 1.49896229e+14])</pre>
</div>
<p>Also included in the <tt class="xref py py-obj docutils literal"><span class="pre">astropy.units</span></tt> package is the
<a class="reference internal" href="../_generated/astropy.units.quantity.Quantity.html#astropy.units.quantity.Quantity" title="astropy.units.quantity.Quantity"><tt class="xref py py-obj docutils literal"><span class="pre">Quantity</span></tt></a> object, which represents a
numerical value with an associated unit. These objects support
arithmetic with other numbers and <a class="reference internal" href="../_generated/astropy.units.quantity.Quantity.html#astropy.units.quantity.Quantity" title="astropy.units.quantity.Quantity"><tt class="xref py py-obj docutils literal"><span class="pre">Quantity</span></tt></a>
objects and preserve units:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">astropy</span> <span class="kn">import</span> <span class="n">units</span> <span class="k">as</span> <span class="n">u</span>
<span class="gp">>>> </span><span class="mf">15.1</span><span class="o">*</span><span class="n">u</span><span class="o">.</span><span class="n">meter</span> <span class="o">/</span> <span class="p">(</span><span class="mf">32.0</span><span class="o">*</span><span class="n">u</span><span class="o">.</span><span class="n">second</span><span class="p">)</span>
<span class="go"><Quantity 0.471875 m / (s)></span>
<span class="gp">>>> </span><span class="mf">3.0</span><span class="o">*</span><span class="n">u</span><span class="o">.</span><span class="n">kilometer</span> <span class="o">/</span> <span class="p">(</span><span class="mf">130.51</span><span class="o">*</span><span class="n">u</span><span class="o">.</span><span class="n">meter</span><span class="o">/</span><span class="n">u</span><span class="o">.</span><span class="n">second</span><span class="p">)</span>
<span class="go"><Quantity 0.0229867443108 km s / (m)></span>
<span class="gp">>>> </span><span class="p">(</span><span class="mf">3.0</span><span class="o">*</span><span class="n">u</span><span class="o">.</span><span class="n">kilometer</span> <span class="o">/</span> <span class="p">(</span><span class="mf">130.51</span><span class="o">*</span><span class="n">u</span><span class="o">.</span><span class="n">meter</span><span class="o">/</span><span class="n">u</span><span class="o">.</span><span class="n">second</span><span class="p">))</span><span class="o">.</span><span class="n">simplify_units</span><span class="p">()</span>
<span class="go"><Quantity 22.9867443108 s></span>
</pre></div>
</div>
</div>
<div class="section" id="votable-xml-support">
<h2>VOTable XML support<a class="headerlink" href="#votable-xml-support" title="Permalink to this headline">¶</a></h2>
<p>The name of the VOTable XML handling package has changed from
<tt class="xref py py-obj docutils literal"><span class="pre">astropy.io.vo</span></tt> to <a class="reference internal" href="../io/votable/index.html#module-astropy.io.votable" title="astropy.io.votable"><tt class="xref py py-obj docutils literal"><span class="pre">astropy.io.votable</span></tt></a>.</p>
<p>The <tt class="xref py py-obj docutils literal"><span class="pre">unit</span></tt> attribute is now an <tt class="xref py py-obj docutils literal"><span class="pre">astropy.units.Unit</span></tt> object, so unit
conversions can easily be supported. The CDS unit format used by
VOTable XML is now fully supported as a result.</p>
<p>Masked values are now handled by a single array, rather than a pair of
arrays.</p>
<p>The <tt class="xref py py-obj docutils literal"><span class="pre">precision</span></tt> and <tt class="xref py py-obj docutils literal"><span class="pre">width</span></tt> attributes of each field are now handled
correctly as per the VOTable XML specification. This may result in
the output changing.</p>
<p>Each <tt class="xref py py-obj docutils literal"><span class="pre">TABLE</span></tt> section of a <tt class="xref py py-obj docutils literal"><span class="pre">VOTable</span></tt> XML file can be converted to/from
an <tt class="xref py py-obj docutils literal"><span class="pre">astropy.table.Table</span></tt> object, which allows much easier editing of
the columns than a regular Numpy structured array.</p>
<p>A standalone <tt class="xref py py-obj docutils literal"><span class="pre">volint</span></tt> script is available to validate the contents of
VOTable XML files.</p>
<p>The default setting for <tt class="xref py py-obj docutils literal"><span class="pre">pedantic</span></tt> mode can be set using a
configuration parameter (<tt class="xref py py-obj docutils literal"><span class="pre">astropy.io.vo.PEDANTIC</span></tt>).</p>
</div>
<div class="section" id="wcs">
<h2>WCS<a class="headerlink" href="#wcs" title="Permalink to this headline">¶</a></h2>
<p>When reading FITS headers, the default value of <tt class="xref py py-obj docutils literal"><span class="pre">relax</span></tt> is <tt class="xref py py-obj docutils literal"><span class="pre">True</span></tt>, in
order to accept all non-standard keywords that <tt class="xref py py-obj docutils literal"><span class="pre">wcslib</span></tt> understands.
This should make <a class="reference internal" href="../wcs/index.html#module-astropy.wcs" title="astropy.wcs"><tt class="xref py py-obj docutils literal"><span class="pre">astropy.wcs</span></tt></a> handle more FITS files by default, but
may introduce a change in behavior in some edge cases. Likewise for
writing FITS headers, the default value of <tt class="xref py py-obj docutils literal"><span class="pre">relax</span></tt> is <tt class="xref py py-obj docutils literal"><span class="pre">WCSHDO_safe</span></tt>,
meaning it will write all non-standard exceptions that are considered
safe and unambiguous. This should make the FITS files produced by
<a class="reference internal" href="../wcs/index.html#module-astropy.wcs" title="astropy.wcs"><tt class="xref py py-obj docutils literal"><span class="pre">astropy.wcs</span></tt></a> supported by a larger range of third-party tools, but
may introduce changes in behavior in some edge cases.</p>
<p>The WCS transformation functions, when provided for a separate array
for each input axis, will now broadcast the arrays correctly and
return the output in the broadcasted shape. This makes using a
constant for one of the axes possible.</p>
<p>The units in a WCS object (<tt class="xref py py-obj docutils literal"><span class="pre">CUNITij</span></tt>) are now <tt class="xref py py-obj docutils literal"><span class="pre">astropy.units.Unit</span></tt>
objects, so operations on those units may be performed.</p>
<p>The included version of <tt class="xref py py-obj docutils literal"><span class="pre">wcslib</span></tt> has been upgraded to version 4.16.</p>
</div>
</div>
</div>
</div>
</div>
<div class="sphinxsidebar">
<div class="sphinxsidebarwrapper"><h3>Page Contents</h3>
<ul>
<li><a class="reference internal" href="#">What’s New in Astropy 0.2</a><ul>
<li><a class="reference internal" href="#ascii-table-i-o">ASCII table I/O</a></li>
<li><a class="reference internal" href="#coordinates">Coordinates</a></li>
<li><a class="reference internal" href="#cosmology">Cosmology</a></li>
<li><a class="reference internal" href="#data-tables">Data Tables</a></li>
<li><a class="reference internal" href="#i-o-framework">I/O framework</a></li>
<li><a class="reference internal" href="#time">Time</a></li>
<li><a class="reference internal" href="#units-and-quantities">Units and quantities</a></li>
<li><a class="reference internal" href="#votable-xml-support">VOTable XML support</a></li>
<li><a class="reference internal" href="#wcs">WCS</a></li>
</ul>
</li>
</ul>
</div>
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