🌌 astroterm

astroterm is a terminal-based star map written in C. It displays the real-time positions of stars, planets, constellations, and more, all within your terminal—no telescope required! Configure sky views by date, time, and location with precise ASCII-rendered visuals. See usage for all supported options!

astroterm is constantly improving, and we'd love to hear your ideas! If you have a suggestion or find a bug, please open an issue and share your feedback.

The night sky above Singapore on January 2, 2025

Features

🔭 Highly Customizable: Choose any date, time, and location to explore past, present, or future celestial events
📐 Accurate Rendering: View the moon, stars, and planets with as much precision as terminal graphics allow
🌘 Moon Phases: Precise lunar phases in real-time
🌌 Constellation Figures: Detailed constellation shapes
⚡ Performance Optimized: Lightweight and fast ASCII rendering

Stars over Sydney, Australia on January 6, 2025

Installation

Several installation methods are provided based on your platform. If none of these fit your needs, you can always build from source. Refer to troubleshooting for help resolving any issues.

Homebrew

You can install Astroterm directly from the custom Homebrew tap:

brew tap da-luce/astroterm
brew install astroterm

Nix

You can try the package in a temporary environment with the following command:

nix-shell -I nixpkgs=channel:nixpkgs-unstable -p astroterm --command astroterm

Argument flags are added by wrapping the command in quotes. For example:

nix-shell -I nixpkgs=channel:nixpkgs-unstable -p astroterm --command "astroterm -u -c"

To make astroterm available from your $PATH, install it with:

nix-env -f channel:nixpkgs-unstable -iA astroterm

Prebuilt Executable

Unix

Download the latest executable using wget
```
wget -O astroterm "https://github.com/da-luce/astroterm/releases/latest/download/astroterm-<os>-<arch>"
```
- Replace <os> with the appropriate platform:
  - Linux: linux
  - macOS: darwin
- Replace <arch> with the appropriate architecture:
  - Linux: x86_64 (arm64 support to come after Ubuntu arm64 runners are avilable)
  - Apple Silicon (M-series): aarch64
  - Intel-based Macs: x86_64
- To view all supported combinations, see the Releases page.
Run the executable
```
chmod +x ./astroterm
./astroterm
```

Windows

Download the latest .exe file using PowerShell's Invoke-WebRequest:

Invoke-WebRequest -Uri "https://github.com/da-luce/astroterm/releases/latest/download/astroterm-win-x86_64.exe" -OutFile "astroterm.exe"

Run the .exe
```
.\astroterm.exe
```

Building from Source

Linux, macOS & WSL

Requirements

Important

When building, you must install the development version of the runtime requirements, which provide the headers and libraries necessary for compiling and linking. These packages are typically marked with a -dev or -devel suffix.

Unix-like environment (Linux, macOS, WSL, etc.)
C compiler
meson 1.4.0 or newer (installation via python is recommended)
ninja 1.8.2 or newer
ncurses library
argtable2
Some common CLI tools
- wget or curl
- xxd (is also commonly packaged with vim)

Warning

ncurses and argtable detection is spotty on some systems, and you may need to install pkg-config in order for Meson to find them.

Tip

See ci.yml for how astroterm is built and tested on Ubuntu via GitHub Actions.

Install

Clone the repository and enter the project directory:

git clone https://github.com/da-luce/astroterm && cd astroterm

Download star data:

curl -L -o data/bsc5 https://web.archive.org/web/20231007085824if_/http://tdc-www.harvard.edu/catalogs/BSC5

Build:

meson setup build
meson compile -C build

You may now run the generated ./build/astroterm binary or add the astroterm command system-wide via meson install -C build. Pressing q or ESC will exit the display.

Windows

Warning

Building on Windows is more involved than other platforms.

Requirements

Microsoft Visual C++ (Other C compilers currently don't work)
meson 1.4.0 or newer (installation via python is recommended)
ninja 1.8.2 or newer
python (for embedding data during build)
pdcurses*
argtable2*

Warning

*These libraries must be compiled locally and moved to where Meson expects them to be. See ci.yml for how this is done.

Install

Clone the repository and enter the project directory:

git clone https://github.com/da-luce/astroterm && cd astroterm

Download star data:

curl -L -o data/bsc5 https://web.archive.org/web/20231007085824if_/http://tdc-www.harvard.edu/catalogs/BSC5

Build:

meson setup build
meson compile -C build

Tip

Some steps must be done in the Visual Studio Developer Command Prompt and Developer PowerShell, so it's best to just do everything there.

Usage

Options

The --help flag displays all supported options:

Usage: astroterm [OPTION]...

  -a, --latitude=<degrees>  Observer latitude [-90°, 90°] (default: 0.0)
  -o, --longitude=<degrees> Observer longitude [-180°, 180°] (default: 0.0)
  -d, --datetime=<yyyy-mm-ddThh:mm:ss>
                            Observation datetime in UTC
  -t, --threshold=<float>   Only render stars brighter than this magnitude
                            (default: 5.0)
  -l, --label-thresh=<float>
                            Label stars brighter than this magnitude (default:
                            0.25)
  -f, --fps=<int>           Frames per second (default: 24)
  -s, --speed=<float>       Animation speed multiplier (default: 1.0)
  -c, --color               Enable terminal colors
  -C, --constellations      Draw constellation stick figures. Note: a
                            constellation is only drawn if all stars in the
                            figure are over the threshold
  -g, --grid                Draw an azimuthal grid
  -u, --unicode             Use unicode characters
  -q, --quit-on-any         Quit on any keypress (default is to quit on 'q' or
                            'ESC' only)
  -m, --metadata            Display metadata
  -r, --aspect-ratio=<float>
                            Override the calculated terminal cell aspect ratio.
                            Use this if your projection is not 'square.' A value
                            around 2.0 works well for most cases
  -h, --help                Print this help message
  -i, --city=<city_name>    Use the latitude and longitude of the provided city.
                            If the name contains multiple words, enclose the
                            name in single or double quotes. For a list of
                            available cities, see:
                            https://github.com/da-luce/astroterm/blob/main/data/
                            cities.csv
  -v, --version             Display version info and exit

Example

Say we wanted to view the sky at 5:00 AM (Eastern) on July 16, 1969—the morning of the Apollo 11 launch at the Kennedy Space Center in Florida. We would run:

astroterm --latitude 28.573469 --longitude -80.651070 --datetime 1969-7-16T8:00:00

Finding the precise coordinates can be cumbersome, so we could also use the nearest major city to achieve a similar result:

astroterm --city Orlando --datetime 1969-7-16T8:00:00 -m

While we're still waiting for someone to invent time travel, we can cheat a little by using Stellarium to confirm that this aligns with reality.

If we then wanted to display constellations and add color, we would add --constellations --color as options.

If you simply want the current time, don't specify the --datetime option and astroterm will use the system time. For your current location, you will still have to specify the --lat and --long options, or provide the nearest city with the --city option.

For more options and help, run astroterm -h or astroterm --help.

Tip

Use a tool like LatLong to get your latitude and longitude.

Tip

Star magnitudes decrease as apparent brightness increases, i.e., to show more stars, increase the threshold.

Troubleshooting

Release Won't Download via Curl

For some reason, curl does not follow the latest release redirect. Use wget to download the latest release or hardcode the tag in the link using curl. Or, just download via the releases page.

Broken Unicode on Linux

If Unicode characters do not display correctly in the terminal, you may need to configure your system's locale to support Unicode.

Temporarily set the locale (add this to .bashrc or equivalent to permanently enforce)

export LC_ALL="en_US.UTF-8"
export LC_CTYPE="en_US.UTF-8"

Install and configure locales (example for Ubuntu/Debian)

sudo apt update
sudo apt install -y locales
sudo dpkg-reconfigure locales

During configuration, select en_US.UTF-8 as the default locale.

Development

ASCII BSC5

You can use the ASCII version of the BSC5 star catalog by downloading and extracting the gzip-compressed file to data/ybsc5 instead of data/bsc5.

Testing

Run meson test within the build directory. To get a coverage report, subsequently run ninja coverage.

Citations

Many thanks to the following resources, which were invaluable to the development of this project.

Map Projections-A Working Manual by John P. Snyder
Wikipedia
Atractor
Jon Voisey's Blog: Following Kepler
Celestial Programming: Greg Miller's Astronomy Programming Page
Practical Astronomy with your Calculator by Peter Duffett-Smith
NASA Jet Propulsion Laboratory
Paul Schlyter's "How to compute planetary positions"
Dan Smith's "Meeus Solar Position Calculations"
Bryan Weber's "Orbital Mechanics Notes"
ASCOM
A Fast Bresenham Type Algorithm For Drawing Ellipses

Data Sources

Stars: Yale Bright Star Catalog
Star names: IAU Star Names
Constellation figures: Stellarium (Converted from Hipparchus to BSC5 indices using the HYG Database—see convert_constellations.py)
Cities: GeoNames (Filtered and condensed using filter_cities.py)
Planet orbital elements: NASA Jet Propulsion Laboratory
Planet magnitudes: Computing Apparent Planetary Magnitudes for The Astronomical Almanac

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README.md

README.md

🌌 astroterm

Table of Contents

Features

Installation

Homebrew

Nix

Prebuilt Executable

Unix

Windows

Building from Source

Linux, macOS & WSL

Requirements

Install

Windows

Requirements

Install

Usage

Options

Example

Troubleshooting

Release Won't Download via Curl

Broken Unicode on Linux

Development

ASCII BSC5

Testing

Citations

Data Sources

Files

README.md

Latest commit

History

README.md

File metadata and controls

🌌 astroterm

Table of Contents

Features

Installation

Homebrew

Nix

Prebuilt Executable

Unix

Windows

Building from Source

Linux, macOS & WSL

Requirements

Install

Windows

Requirements

Install

Usage

Options

Example

Troubleshooting

Release Won't Download via Curl

Broken Unicode on Linux

Development

ASCII BSC5

Testing

Citations

Data Sources