sourcefinder.accessors.fitsimage
================================

.. py:module:: sourcefinder.accessors.fitsimage


Attributes
----------

.. autoapisummary::

   sourcefinder.accessors.fitsimage.logger


Classes
-------

.. autoapisummary::

   sourcefinder.accessors.fitsimage.FitsImage


Module Contents
---------------

.. py:class:: FitsImage(url, plane=None, beam=None, hdu_index=0)

   Bases: :py:obj:`sourcefinder.accessors.dataaccessor.DataAccessor`


   
   Use PyFITS to pull image data out of a FITS file.

   Provide standard attributes, as per :class:`DataAccessor`. In addition, we
   provide a ``telescope`` attribute if the FITS file has a ``TELESCOP``
   header.

   :Parameters:

       **url** : Path or str
           The path or URL to the FITS file.

       **plane** : int, default: None
           If the data is a datacube, specifies which plane to use.

       **beam** : tuple, default: None
           Beam parameters in degrees, in the form (bmaj, bmin, bpa). If not
           supplied, the method will attempt to read these from the header.

       **hdu_index** : int, default: 0
           The index of the HDU to use from the HDU list.














   ..
       !! processed by numpydoc !!

   .. py:method:: _get_header(hdu_index)

      
      Retrieve the header from the specified HDU in the FITS
      file.


      :Parameters:

          **hdu_index** : int
              The index of the Header Data Unit (HDU) to extract the header from.



      :Returns:

          astropy.io.fits.Header
              A copy of the header from the specified HDU.











      ..
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   .. py:method:: calculate_phase_centre()

      
      Calculate the phase center of the FITS image.

      The phase center is determined by finding the central pixel and
      converting that position to celestial coordinates.




      :Returns:

          tuple[float]
              A tuple containing the right ascension and declination of
              the phase center in degrees.











      ..
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   .. py:method:: parse_beam()

      
      Read and return the beam properties bmaj, bmin and bpa
      values from the FITS header.





      :Returns:

          **bmaj** : float
              the major axis of the beam in degrees.

          **bmin** : float
              the minor axis of the beam in degrees.

          **bpa** : float
              the position angle of the beam in degrees.








      .. rubric:: Notes

      AIPS FITS file: stored in the history section



      ..
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   .. py:method:: parse_coordinates()

      
      Parse header to return a WCS (World Coordinate System)
      object.





      :Returns:

          WCS
              A WCS object containing the coordinate system information
              extracted from the FITS file header.




      :Raises:

          TypeError
              If the coordinate system is not specified in the FITS header.




      .. rubric:: Notes

      If units are not specified in the header, degrees are assumed by
      default.



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          !! processed by numpydoc !!


   .. py:method:: parse_frequency()

      
      Set some 'shortcut' variables for access to the frequency
      parameters in the FITS file header.





      :Returns:

          **freq_eff** : float
              The effective frequency extracted from the FITS header.

          **freq_bw** : float
              The bandwidth extracted from the FITS header.











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   .. py:method:: parse_start_time()

      
      Parse and return the start time of the observation, that
      yielded this FITS image, from its header.





      :Returns:

          datetime.datetime
              The start time of the observation as an instance of
              `datetime.datetime`.




      :Raises:

          KeyError
              If the timestamp in the FITS file is unreadable.

          Warning
              Logged if a non-standard date format is encountered in the FITS
              file.







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   .. py:method:: parse_times()

      
      Attempt to do something sane with timestamps.





      :Returns:

          **taustart_ts** : datetime.datetime
              Timezone-naive (implicit UTC) datetime representing the
              start of the observation.

          **tau_time** : float
              Integration time in seconds.











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   .. py:method:: read_data(hdu_index, plane)

      
      Read data from our FITS file.


      :Parameters:

          **hdu_index** : int
              The index of the Header Data Unit (HDU) to extract the data from.

          **plane** : int, default: None
              If the data is a datacube, specifies which plane to use.



      :Returns:

          numpy.ndarray
              The processed 2D data array, transposed for intuitive display.








      .. rubric:: Notes

      PyFITS reads the data into an array indexed as [y][x]. We
      take the transpose to make this more intuitively reasonable and
      consistent with (eg) ds9 display of the FitsFile. Transpose back
      before viewing the array with RO.DS9, saving to a FITS file,
      etc.



      ..
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   .. py:attribute:: data


   .. py:attribute:: header


   .. py:attribute:: pixelsize


   .. py:attribute:: url


   .. py:attribute:: wcs


.. py:data:: logger