Wrote docs for FieldOfView

docs/fov.rst

@@ -0,0 +1,67 @@
+.. _fov:
+
+About fields of view
+====================
+
+Fields of view (FOVs) are pre-loaded annotations that provide approximate 
+projections of how instruments from major telescopes look on the sky, which is 
+useful in simulating observing runs. FOVs for existing instruments (such as 
+those from NASA's Hubble and Spitzer Space Telescopes), future instruments on 
+the James Webb Space Telescope, and larger footprints like the field of the K2 
+mission come out of the box and ready to use with pyWWT.
+
+(If you have an instrument you'd like to simulate, you can still use the methods 
+from :ref:`foo_bar` to plot it, but please also consider forwarding its 
+dimensions and further information to us on GitHub. We are especially interested 
+in adding more footprints from other sky surveys.)
+
+
+Plotting an instrument
+----------------------
+
+Use the :meth:`~pywwt.BaseWWTWidget.add_fov` method to add a pre-loaded FOV to 
+the viewer::
+
+    >>> from astropy import units as u
+    >>> from astropy.coordinates import SkyCoord
+    >>> 
+    >>> hdf = SkyCoord(189.206, 62.216, unit=u.deg)
+    >>> wwt.background = wwt.imagery.visible.sdss
+    >>> wwt.center_on_coordinates(hdf, fov=2.8*u.arcmin)
+    >>>
+    >>> # recreate the Hubble Deep Field image
+    >>> fov = wwt.add_fov(wwt.instruments.hst_wfc3_ir, center=hdf,
+    ...                   rotate=12*u.deg, line_color='#D4BD8A')
+    
+.. image:: images/hdf.png
+
+Only certain instrument names are accepted, so be sure to use the 
+:obj:`pywwt.instruments.Instruments` object in selecting the proper one. To see 
+which instruments are currently available, either use tab-completion in an 
+interactive interpreter with :obj:`pywwt.instruments.Instruments`, or return a 
+list like so::
+
+    >>> wwt.instruments.available
+    ['hst_acs_wfc',
+    'hst_wfc3_ir',
+    'hst_wfc3_uvis',
+    'jwst_nircam',
+    'jwst_niriss',
+    'k2',
+    ''spitzer_irac']
+    
+For :meth:`~pywwt.BaseWWTWidget.add_fov`, the instrument name is the only 
+required argument; center defaults to the center of your view and rotation 
+defaults to 0. Additionally, since FOVs are drawn as polygons, editable 
+properties for annotations (see :class:`~pywwt.Polygon` for a full list) work as 
+trailing keyword arguments, just as ``line_color`` did in the earlier example 
+function call.
+
+Once an FOV is no longer needed, it can be removed from view via its 
+:meth:`~pywwt.FieldOfView.remove` method. 
+:meth:`~pywwt.BaseWWTWidget.clear_annotations` will also clear FOVs in addition 
+to regular annotations.
+
+.. note:: Due to the spherical projection system used by WWT, FOVs warp near the 
+poles. This especially true for FOVs that are larger in size, contain multiple 
+panels, or have been rotated.

docs/screenshots.py

@@ -22,7 +22,7 @@ line.color = 'salmon'
 wwt.wait()
 wwt.render('images/big_dipper2.png')
 
-# polygon.png
+# polygons.png
 wwt.center_on_coordinates(SkyCoord.from_name('eta orion'))
 wwt.crosshairs = False
 
@@ -96,3 +96,21 @@ wwt.foreground = 'Planck Dust & Gas'
 wwt.foreground_opacity = .75
 wwt.wait()
 wwt.render('images/dust_on_gamma.png')
+
+# universe.png
+wwt.set_view('universe')
+
+wwt.wait()
+wwt.render('images/universe.png')
+
+# hdf.png
+wwt.set_view('sky')
+wwt.clear_annotations()
+
+hdf = SkyCoord(189.206, 62.216, unit=u.deg)
+wwt.background = wwt.imagery.visible.sdss
+wwt.center_on_coordinates(hdf, fov=2.8*u.arcmin)
+fov = wwt.add_fov(wwt.instruments.hst_wfc3_ir, center=hdf,
+                  rotate=12*u.deg, line_color='#D4BD8A')
+wwt.wait()
+wwt.render('images/hdf.png')