Astroterm is a lightweight, terminal-based planetarium designed to visualize the night sky without the need for a telescope or a graphical user interface. Written in C, the tool renders the real-time positions of celestial bodies—including stars, planets, and constellations—directly within a command-line environment. It allows users to explore past, present, or future celestial events by configuring specific dates, times, and geographic locations. The application is optimized for performance, providing fast ASCII-rendered visuals that can be customized to show specific lunar phases or detailed constellation figures.
The image illustrates the primary function of Astroterm as a terminal-based planetarium.
The tool functions by calculating celestial positions based on observer coordinates and specific timestamps. Users can input their exact latitude and longitude or select a major city to automatically retrieve its coordinates. The rendering engine supports several visual enhancements, such as terminal colors, azimuthal grids, and the ability to toggle constellation stick figures. For those seeking high-density visuals, the software includes a threshold setting to determine the brightness of stars to be rendered; increasing this threshold allows for a more populated star map, while decreasing it focuses on the brightest objects. It also supports Braille characters to represent constellation lines, providing a more nuanced visual representation than standard ASCII characters alone.
While Astroterm provides a high-fidelity representation of the sky within the constraints of a text-based interface, it is intended as a complementary tool rather than a replacement for professional astronomical software. The developer notes that users can cross-reference Astroterm's output with tools like Stellarium to verify celestial alignments. Because terminal cell aspect ratios can vary, the tool includes an aspect-ratio override flag to ensure that projections remain accurate on non-square terminal layouts. The project is currently available across multiple platforms, including Linux, macOS, and Windows, with installation support for package managers like Homebrew, Nix, and Guix.