Sky & Telescope Stellarium Skyculture

Constellation Shapes

Generating constellationship.fab

The constellation shapes (constellationship.fab) are generated using the generate_constellationship.py script. This script accepts Sky & Telescope's constellation data (SnT_constellations.txt) on STDIN, and returns Stellarium's constellation shape syntax to STDOUT. Diagnostic and progress data are printed to STDERR.

To generate a new constellationship.fab file:

# Create a Python virtualenv to work in
$ virtualenv -p /usr/bin/python3 python_virtualenv
$ . python_virtualenv/bin/activate
$ pip install astroquery percache

# Generate the constellationship.fab file
$ ./generate_constellationship.py < SnT_constellations.txt > constellationship.fab

# (optional) force doing new VizieR queries
$ rm .hip_cache

Data lookup and caching

The script queries the VizieR service (http://vizier.u-strasbg.fr/viz-bin/VizieR) to translate the RA/Dec line endpoints in the S&T data, to Hipparcos catalog IDs used by Stellarium. Since querying VizieR can take a while (a few seconds for each star), a cache is implemented so that previous results are cached in the .hip_cache file for use by subsequent runs of the script. If you make changes to the get_hip() function, you should delete the .hip_cache file to ensure that you don't return cached values.

Translation caveats

Line weight

Sky & Telescope draws constellation lines with various line weights. For example, the "teaspoon" asterism to the east of the "teapot" of Sagittarius is drawn using lighter lines than the primary constellation.

Stellarium does not have any way to draw different weights of constellation lines, so generate_constellationship.py simply draws all of them. It would be relatively easy to build in a filter so that it only includes the heaviest weighted lines, but for the purposes of trying to make Stellarium's lines look the most like what you see in a Sky & Telescope atlas, having all of the lines is preferable.

Non-constellation stars

Sky & Telescope uses a convention of terminating constellation lines that end at a star outside the constellation (for example, Alpheratz in Pegasus) a half-degree short of the target star. Stellarium's constellation line drawing feature requires that all lines terminate at stars.

Missing constellations

Sky & Telescope does not provide constellation lines for Microscopium and Mensa. Thus the computed constellationship.fab file contains only 86 of the 88 constellations.

Star Names

Sky & Telescope provided a Word document (SnT_star_names.docx) that contain the names of the stars used in Sky & Telescope publications. A script is provided (generate_star_names.py) that is able to extract the star names from this file, look up each star in the Hipparcos catalog (using VizieR), and return a star_names.fab formatted output.

Usage

To generate a new star_names.fab file:

# Create a Python virtualenv to work in
$ virtualenv -p /usr/bin/python3 python_virtualenv
$ . python_virtualenv/bin/activate
$ pip install astroquery percache python-docx

# Generate the star_names.fab file
$ ./generate_star_names.py SnT_star_names.docx > star_names.fab

# (optional) force doing new VizieR queries
$ rm .hip_cache_stars