Target Details
The Andromeda Galaxy (Messier 31) is a spiral galaxy approximately 2.5 million light-years from Earth. It is in the constellation of Andromeda. Being approximately 220,000 light years across, it is the largest galaxy of the Local Group, which also contains the Milky Way, the Triangulum Galaxy, and about 44 other smaller galaxies. 

The Milky Way and Andromeda galaxies are expected to collide in 4.5 billion years, eventually merging to form a giant elliptical galaxy or perhaps a large disc galaxy. The apparent magnitude of the Andromeda Galaxy, at 3.4, is among the brightest of the Messier objects, making it visible to the naked eye on moonless nights, even when viewed from areas with moderate light pollution.

Capture Details 
Data captured over numerous session in August & September 2017.
4 Pane Mosaic in 2x2 Layout
136x 10 minute exposures at ISO400 across the 4 panes.

Equipment Details 
Skywatcher Quattro 200 CF
NEQ6 Pro
Canon 40d (IR Filter removed)
Skywatcher ST-80
QHY5L-II 

Processing Details 
This image was processed in Pixinsight & Lightroom.

Processing Individual Panes
Calibration and Stacking of each pane seperately.
Dynamic Crop - Each pane was cropped to remove any black edges. 
Fast Rotation - To orient pane as it will be located in mosaic
Dynamic Background Extraction - Applied to each pane to remove background gradients. 
Photometric Colour Calibration - To colour calibrate the image.
SCNR - To neutralise green.
Deconvolution - To bring out some fine detail. (Not very effective in this image due to lack of good data)

To Create Mosaic
Star Alignment - To create mosaic layout and registration data. 
Gradient Merge Mosaic - To create mosiac image.

Processing Mosaic
Dynamic Crop - To remove black edges and gaps in the mosaic.
Multiscale Linear Transform - Noise reduction.
Histrogram Transformation - To stretch the image and bring out the data.
HDR Multiscale Transform - To recover additional data in core.
Curves Transformation - To increase contrast.
Local Histogram Equialisation - To sharpen & increase detail.
Histogram Transformation - To darken background, using RangeMask to protect galaxy centre.
Dark Structure Enhance - To increase contrast in arms / bands.
Curves Transformation - To improve contrast on entire image.
Curves Transformation - To darken background, using Rangemask to protect galaxy.

Export as JPEG and import into Lightroom.
Increase Contrast (+20)
Increase Saturation (+35)

Export final JPEG for upload.