The Andromeda Galaxy (M31)

The Andromeda Galaxy (Messier 31), the largest galaxy in the Local Group, 2.5 million light-years away – photographed by Pete Lawrence.

Target details

The Andromeda Galaxy (Messier 31) is a spiral galaxy about 2.5 million light-years away. At around 220,000 light-years across it's the largest galaxy in the Local Group, which also includes the Milky Way, the Triangulum Galaxy and about 44 smaller galaxies. At magnitude 3.4 it's one of the brightest Messier objects, visible to the naked eye on moonless nights even from areas with moderate light pollution. Andromeda and the Milky Way are expected to collide in about 4.5 billion years, eventually merging into one giant galaxy.

Capture details

Data captured 7th & 8th August, 2017.
4 Pane Mosaic in 2x2 Layout
40x 2 minute exposures at ISO400 per pane.
This was a test session to get a feel for the creation of a mosaic in PixInsight. The data was captured under a full moon.

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.

Calibration and Stacking of each pane seperately.
Dynamic Crop - Each pane was cropped to remove any black edges.
Automatic Background Extraction - Applied to each pane to remove background gradients.
Star Alignment - To create mosaic layout and registration data.
Gradient Merge Mosaic - To create mosiac image.

Dynamic Crop - To remove black edges and gaps in the mosaic.
Photometric Colour Calibration - To colour calibrate the image.
SCNR - To remove green tinge.
Deconvolution - To bring out some fine detail. (Not very effective in this image due to lack of good data)
Multiscale Linear Transform - Noise reduction.
Histrogram Transformation - To stretch the image and bring out the data.
Curves Transformation - To increase contrast.
Histogram Transformation - To darken background, using RangeMask to protect galaxy centre.
Histogram Transformation - To darken background, using StarMask to protect stars.
Curves Transformation - To add more contrast, using StarMask to protect stars.

Export as JPEG and import into Lightroom.
Darken blacks slightly (-15)
Use local adjustment brush to darken some artifacts from merge process. (-.05 stop exposure)
Increase saturation (+25)
Export final JPEG for upload.
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