Index: docs/sphinx-docs/source/user/sasgui/perspectives/calculator/resolution_calculator_help.rst
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+.. resolution_calculator_help.rst
+
+.. This is a port of the original SasView html help file to ReSTructured text
+.. by S King, ISIS, during SasView CodeCamp-III in Feb 2015.
+
+Q Resolution Estimator Tool
+===========================
+
+Description
+-----------
+
+This tool is approximately estimates the resolution of Q from SAS instrumental 
+parameter values assuming that the detector is flat and normal to the 
+incident beam.
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+Using the tool
+--------------
+
+1) Select *SAS Resolution Estimator* from the *Tool* menu on the SasView toolbar.
+
+2) Select the source (Neutron or Photon) and source type (Monochromatic or TOF).
+
+   *NOTE! The computational difference between the sources is only the 
+   gravitational contribution due to the mass of the particles.*
+
+3) Change the default values of the instrumental parameters as required. Be 
+   careful to note that distances are specified in cm!
+
+4) Enter values for the source wavelength(s), |lambda|\ , and its spread (= FWHM/|lambda|\ ).
+   
+   For monochromatic sources, the inputs are just one value. For TOF sources, 
+   the minimum and maximum values should be separated by a '-' to specify a 
+   range.
+   
+   Optionally, the wavelength (BUT NOT of the wavelength spread) can be extended 
+   by adding '; nn' where the 'nn' specifies the number of the bins for the 
+   numerical integration. The default value is nn = 10. The same number of bins 
+   will be used for the corresponding wavelength spread.
+
+5) For TOF, the default wavelength spectrum is flat. A custom spectral 
+   distribution file (2-column text: wavelength (|Ang|\) vs Intensity) can also 
+   be loaded by selecting *Add new* in the combo box.
+
+6) When ready, click the *Compute* button. Depending on the computation the 
+   calculation time will vary.
+
+7) 1D and 2D dQ values will be displayed at the bottom of the panel, and a 2D 
+   resolution weight distribution (a 2D elliptical Gaussian function) will also 
+   be displayed in the plot panel even if the Q inputs are outside of the 
+   detector limit (the red lines indicate the limits of the detector).
+   
+   TOF only: green lines indicate the limits of the maximum Q range accessible 
+   for the longest wavelength due to the size of the detector.
+    
+   Note that the effect from the beam block/stop is ignored, so in the small Q 
+   region near the beam block/stop 
+
+   [ie., Q < 2. |pi|\ .(beam block diameter) / (sample-to-detector distance) / |lambda|\_min] 
+
+   the variance is slightly under estimated.
+
+8) A summary of the calculation is written to the SasView *Console* at the 
+   bottom of the main SasView window.
+
+.. image:: resolution_tutor.gif
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+Theory
+------
+
+The scattering wave transfer vector is by definition
+
+.. image:: q.gif
+
+In the small-angle limit, the variance of Q is to a first-order 
+approximation
+
+.. image:: sigma_q.gif
+
+The geometric and gravitational contributions can then be summarised as
+
+.. image:: sigma_table.gif
+
+Finally, a Gaussian function is used to describe the 2D weighting distribution 
+of the uncertainty in Q.
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+References
+----------
+
+D.F.R. Mildner and J.M. Carpenter 
+*J. Appl. Cryst.* 17 (1984) 249-256
+
+D.F.R. Mildner, J.M. Carpenter and D.L. Worcester 
+*J. Appl. Cryst.* 19 (1986) 311-319
+
+.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
+
+.. note::  This help document was last changed by Steve King, 01May2015
