Refine flat field fit from scratch

This simplifies the fitting of flat field correction by directly refining the fit instead of doing the former fit on the ratio of 2 different beam orders and having to define proper threshold.

doc/changelog.rst

@@ -6,13 +6,15 @@ unreleased
 
 - **Bug fixes**
 
-    - fix :issue:`45` SLURM scripts embedded in and download link available from documentation :mr:`171`
-    - fix :issue:`8` regarding azimuthal integration with pyFAI and hexagonal DSSC pixel splitting by providing an example notebook :mr:`174`
+    - fix :issue:`45` SLURM scripts embedded in and download link available
+      from documentation :mr:`171`
+    - fix :issue:`8` regarding azimuthal integration with pyFAI and hexagonal
+      DSSC pixel splitting by providing an example notebook :mr:`174`
     - fix :issue:`46` with a change in dask groupby mean behavior :mr:`174`
     - fix :issue:`47` SLURM script not using the correct kernel :mr:`176`
     - fix :issue:`51` make sure that BAM units are in ps :mr:`183`
     - fix :issue:`50` and :issue:`54` relating to package dependencies
-		- fix :issue:`57` adds target mono energy mnemonic
+    - fix :issue:`57` adds target mono energy mnemonic
     - fix :issue:`55` implementingd dask auto rechunking in notebooks
     - fix :issue:`53` wrong flat field correction sometimes being calculated 
     - fix :issue:`56` future warning on xarray.ufuncs :mr:`189`
@@ -28,8 +30,11 @@ unreleased
       in the BOZ analysis, including fitting domain functions, hexagonal
       pixel lattice, possibility to switch off flat field symmetry constraints
       and a refine fit function with regularization term :mr:`186`
- 
+    - simplifies flat field calculation by using directly the refined fit
+      procedure which works with far fewer input parameters :mr:`202`
+
 - **New Features**
+
     - add routine for fluence calibration :mr:`180`
     - add Fast ADC 2 mnemonics :mr:`200`