Constellations from Around the World

This repository explains how to make a map of constellations from cultures around the world, using data from Stellarium and the HYG Database (Hipparcos, Yale Bright Star, and Gliese catalogs). Software used includes Python 3.7.1, Illustrator CC 2019 and Photoshop CC 2019. If you have comments or suggestions for this tutorial, please let me know on my blog! You can also buy the finished map here if you like.

Python dependencies: matplotlib numpy cartopy pandas glob os jupyter. Dependencies can be installed with pip install -r requirements.txt.

Special instructions for beginners

If you're new to coding:

Software Carpentry has great tutorials for installing Python (scroll down and follow the directions in the Bash Shell and Python sections), getting starting with Jupyter Notebooks, and beginner-friendly Python programming. After you've installed Python using these tutorials, you can use Git Desktop and the instructions in this tutorial to download the code and data in this tutorial.

If you're new to design:

You'll need software for editing raster and vector images (this article explains the difference). I use Adobe Photoshop and Illustrator, but you can also use the free open-source programs Gimp and Inkscape. There is no perfect software that fits everyone's needs, so you'll want to understand the pros and cons for the different raster and vector programs before choosing.

Table of Contents

1. Gathering and processing data
2. Map design in Python
3. Map design in Illustrator and Photoshop
4. References
5. License

HYG Database version 3, which combines all stars from the Hipparcos, Yale Bright Star, and Gliese catalogs. This dataset provides the right ascension (RA) and declination (DEC) for each star - the celestial equivalent of longitude and latitude - as well as the spectral class, magnitude, name, ID number, and various other measurements. I edited the original dataset in 1_process_starbase_data.ipynb to only include visible stars (magnitude <= 6.5).

Asterisms from Around the World

What we call "constellations" in popular English are actually unofficial shapes called asterisms (examples from Arabic and Korean cultures shown below). I downloaded these asterisms from Stellarium, an open-source planetarium software. In the Stellarium Git repository, these asterisms are found in the skycultures folder as the file constellationship.fab and constellation_names.eng.fab for each culture. This data is provided as a list of star ID numbers that should be connected to form each of the lines in the asterisms. To plot the asterisms on a map, I matched each star ID number to the same entry in the HYG Database, and converted ID number into RA and DEC location values for each asterism vertex.

The stars around the Western constellation Orion are one of the busiest places on the map. Some of the individual cultures are highlighted below, including the Chinese constellations in red, ancient Egyptian in turquoise, and Arabic in green. I really liked that each of these cultures included the triple stars in “Orion’s belt”, but still interpreted the star patterns in a completely different design.

Earth Homes

I also wanted to map each of the cultures on the Earth to show where each group of people were from. For this map I used vector data from cartopy to plot the coastline of all continents. I also used topography data downloaded from the NASA Near-Earth Observations website to add a subtle texture to the basic shape outline.

For many of the cultures, especially the ancient ones, it was difficult to pick an exact location to use for this map. So I decided to use very large markers to show just the approximate location. The exact data points used in the colormap.csv dataset are based off of cities that were probably or definitely a part of that culture, and don't necessarily show the most important city.

Map Projections

I used a Plate Carrée projection for this map, because the perpendicular gridlines make it easy to read coordinates (which are useful for finding stars that rise and set throughout the night). However, Plate Carrée tends to distort maps quite a bit, so it's rarely used. The same code in this repository can be used to create maps in any other supported projection by changing the axis projection variable plt.axes(projection=cartopy.crs.PlateCarree()).

To show the stars and asterisms near the North and South poles - which are distorted particularly heavily in Plate Carrée - I also included two inset maps at the bottom of the design in an Orthographic projection. There's no real difference in the design steps used to make these two additional maps, except for changing the projection in Python before plotting.

font alternates and ligatures, custom brushes, layering effects, blur effects, gradients along a path, variable width paths, type on a path, and selecting objects by characteristic.

Layering in Photoshop

I've included a small section of the map in the figures folder as the Photoshop file worldstars_sample.psd. It still has the original layers, so you should be able to use it as a reference for layering and color effects.

Shadows and Glow Effects

To create a glow effect around the asterisms, duplicate the asterism color layer and go to Filter --> Blur Gallery --> Field Blur. For glowing text or objects I usually create two blur layers set to 20% opacity - one with a Blur of 4px and the other 10px. In this map I added a glow effect to the text labels and all of the asterisms.

I also added a light shadow underneath the text labels to make them easier to read. You can make this shadow effect in almost exactly the same way as the glow effect: Before applying the Field Blur, change the color of all text objects in the duplicated layer to the color you'd like to use for the shadow. I think it's easiest to change the colors in the original Illustrator image instead of in Photoshop (especially for text and complex object shapes).

Color and Font

I wanted the maps in this series to look cohesive, so I made a palette of ~70 different colors and picked from these choices in every map. I also used the same two fonts (Redflowers and Moon) in all maps. You're welcome to use the color palette and font styling if you'd like.

The color scheme for this map was inspired by antique roadmaps, like this map of Nebraska from 1898. But this is the only map in the series without a dark background, and I wasn’t quite convinced that a lighter background could work for a star map. I even made two different versions before finally deciding to stick with the original color scheme.

• Astronomy. Andrew Fraknoi, David Morrison, Sidney C. Wolff et al. OpenStax 2016.
• HYG Database version 3. David Nash. 2019.
• Stellarium 2019 version 0.19.0.
• Fonts: Moon by Jack Harvatt and RedFlower by Type & Studio.
• Advice: Thank you to Nadieh Bremer, Oliver Fraser, Chloe Pursey, and Leah Willey for their helpful advice in making this map.

GPL-3.0 license.

Data: The data in this repository belongs to the original authors of the data. Please use the references section to look up the original version. In cases where I edited or revised the data, I impose no additional restrictions to the original license. Any data files I created myself are shared under the ODC Open Database License.

Artwork: The artwork included in this repository are shared under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.