Merge pull request #149 from rosteen/intro-docs

Add summary of capabilities/user stories to docs index page

docs/index.rst

@@ -2,13 +2,28 @@
 Specreduce Documentation
 ########################
 
-The `specreduce <https://specreduce.readthedocs.io/en/latest/index.html>`_ package aims to provide a data reduction toolkit for optical
+The `specreduce <https://specreduce.readthedocs.io/en/latest/index.html>`_ package
+aims to provide a data reduction toolkit for optical
 and infrared spectroscopy, on which applications such as pipeline processes for
 specific instruments can be built. The scope of its functionality is limited to
-basic spectroscopic reduction, with basic *image* processing steps (such as
-bias subtraction) instead covered by `ccdproc <https://ccdproc.readthedocs.io/en/latest/>`_ and other packages, data
-analysis by `specutils <https://specutils.readthedocs.io/en/latest/>`_ and visualization by `matplotlib <https://matplotlib.org/>`_. A few
-examples will nevertheless be provided of its usage in conjunction with these
+basic spectroscopic reduction, currently encompassing the following three tasks:
+
+#. Determining the trace of a spectrum dispersed in a 2D image, either by setting a flat
+   trace, providing a custom trace array, or fitting a spline, polynomial, or other model
+   to the positions of the dispersed spectrum.
+#. Generating a background based on a region on one or both sides of this trace, and making
+   available the background image, 1D spectrum of the background, and the
+   background-subtracted image.
+#. Performing either a Horne (a.k.a. "optimal") or boxcar extraction on either the original
+   or background-subtracted 2D spectrum, using the trace generated by the first task to
+   generate a 1D spectrum.
+
+Further details about these capabilities are detailed in the sections linked below.
+Beyond these tasks, basic *image* processing steps (such as bias subtraction) are covered by
+`ccdproc <https://ccdproc.readthedocs.io/en/latest/>`_
+and other packages, data analysis by `specutils <https://specutils.readthedocs.io/en/latest/>`_,
+and visualization by `matplotlib <https://matplotlib.org/>`_. A few
+examples will be provided that feature ``specreduce`` in conjunction with these
 complementary packages.
 
 .. note::