🌌 astroterm

astroterm is a terminal-based celestial viewer written in C using ncurses. 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 above Singapore on January 2, 2025

Table of Contents

• Features
• Installation
  • Linux
  • MacOS
  • Windows
• Building from Source
• Usage
• Troubleshooting
• Citations
• Data Sources

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.

Linux

Prebuilt Executable

1. Download the latest executable using wget

   wget -O astroterm-linux-x86_64 "https://github.com/da-luce/astroterm/releases/latest/download/astroterm-linux-x86_64"

2. Run the executable

   chmod +x ./astroterm-linux-x86_64
   ./astroterm-linux-x86_64

MacOS

Prebuilt Executable

1. Download the latest executable for your system architecture using wget

   wget -O astroterm-darwin-<arch> "https://github.com/da-luce/astroterm/releases/latest/download/astroterm-darwin-<arch>"

   • Replace <arch> with the appropriate architecture:
     • Apple Silicon (M-series): astroterm-darwin-aarch64
     • Intel-based Macs: astroterm-darwin-x86_64

2. Run the executable

   chmod +x ./astroterm-darwin-<arch>
   ./astroterm-darwin-<arch>

Windows

Prebuilt Executable

1. 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-win-x86_64.exe"

2. Run the .exe

   .\astroterm-win-x86_64.exe

Or, download via the Releases Page.

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

1. Clone the repository and enter the project directory:

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

2. Download star data:

curl -L -o data/bsc5 http://tdc-www.harvard.edu/catalogs/BSC5

3. 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 (not recommended)

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

1. Clone the repository and enter the project directory:

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

2. Download star data:

curl -L -o data/bsc5 http://tdc-www.harvard.edu/catalogs/BSC5

3. 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 (def
                            ault: 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 constella
                            tion is only drawn if all stars in the figure are o
                            ver 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 valu
                            e 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 avai
                            lable cities, see: https://github.com/da-luce/astro
                            term/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.

1. 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"

2. 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.

Broken Resizing on Windows

Currently, resizing the terminal on Windows is not functioning properly due to known incompatibilities. At this time, no solutions are available. Contributions or suggestions to address this issue are greatly appreciated.

Development

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