Refs #9587 - Docs for ConvertSpectrumAxis V1.

Shamelessly steal from Martyns V2 docs.

Code/Mantid/docs/source/algorithms/ConvertSpectrumAxis-v1.rst

@@ -23,4 +23,25 @@ generated by using the :ref:`algm-ConvertUnits` methods to
 translate the values of the first and last bin for the current X-data
 unit into the target unit, then taking the mid-point of these.
 
+Usage
+-----
+
+**Example: Convert Vertical Axis to Theta**
+
+.. testcode::
+
+   # Creates a workspace with some detectors attached
+   dataws = CreateSampleWorkspace(NumBanks=1,BankPixelWidth=2) # 2x2 detector
+
+   theta = ConvertSpectrumAxis(dataws, Target="theta", Version=1)
+
+   vertical_axis = theta.getAxis(1)
+   print "There are %d axis values" % vertical_axis.length()
+   print "Final theta value: %f (degrees)" % vertical_axis.getValue(vertical_axis.length() - 1)
+
+.. testoutput::
+
+   There are 4 axis values
+   Final theta value: 0.129645 (degrees)
+
 .. categories::