Though we often think of GIS as focused on the earth, ArcGIS Pro is powerful enough to map the heavens above. We love how this star chart and companion story map use vivid illustrations and clear explanations for celestial mapping terms such as coordinates and constellation boundaries. The charts make great use of colour and labels, and the map offers a beautiful depiction of the arc of the Milky Way across the sky. Minimal constellation figures in the overview maps help us to quickly orient ourselves in the night sky.
Charting the stars is something most of us have never tried. This map presents the endeavour as an approachable map-making process using clever cartographic techniques for spectacular visualisation. The gracefully implemented graduated symbology represents the stars’ relative brightness. This technique gives the chart stunning depth atop intuitive nighttime colours. Larger areas of the night sky are made prominent by a smart labelling hierarchy. Well-crafted annotation further enhances the labels. A clean layout brings together Northern and Southern hemisphere charts. Each symbolisation technique makes this very dense dataset beautifully legible.
You can read a Story Map of the steps involved.
Instead of latitude and longitude coordinates, star charts use declination and right ascension. In ArcGIS Pro, you can make a spatial layer of your star chart table by making an XY Event Layer and setting the Declination as the Y field.
Use the Polar Stereographic projection. Since it is conformal, constellations can retain their recognisable shapes. Remember to make a map for each hemisphere to capture the entire night sky.
Dividing the Northern and Southern hemispheres into their own views, and rotating the Southern hemisphere by 180 degrees, will allow you to display the Milky Way as a continuous feature across both views.
Using graduated symbology to indicate star brightness will give your star chart depth.
Data sources: Data was compiled by Peter Girard, who gave permission to use and share it [ZIP]. The only missing piece was the Milky Way, which was adapted from another map.
Software: ArcGIS Pro, ArcMap, Inkscape
The chart required manipulation of data and graphics. For example, the author used georeferencing and custom projections to create the Milky Way polygons, and the Feature Outline Masks tool for annotation masking.
Using the provided data, and without agonising over any design considerations, you could recreate this map in one or two days. Most of the work is in placing and editing text. It took about four months of experimentation to arrive at this final map.
Polar Stereographic projection provides great results.
Use separate views for the Northern and Southern hemispheres, rotating the Southern Hemisphere by 180 degrees.
The stars’ relative brightness value can serve as the field by which to apply graduated symbology.
Heather Smith is a cartographer and artist. She works at Esri designing and testing symbology features in ArcGIS Pro.
A Sky Without Stars
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