graph LR
skyfield_positionlib["skyfield.positionlib"]
skyfield_framelib["skyfield.framelib"]
skyfield_toposlib["skyfield.toposlib"]
skyfield_geometry["skyfield.geometry"]
skyfield_projections["skyfield.projections"]
skyfield_framelib -- "provides rotation matrices to" --> skyfield_positionlib
skyfield_toposlib -- "provides observer locations to" --> skyfield_positionlib
skyfield_geometry -- "provides geometric calculations to" --> skyfield_positionlib
skyfield_positionlib -- "provides position data for projections to" --> skyfield_projections
The skyfield subsystem is designed around a core positionlib component that manages astronomical positions and their transformations. This core component is supported by framelib, which provides the essential rotational mechanics for coordinate system conversions, and geometry, which offers fundamental geometric utilities. toposlib extends the system by enabling calculations from specific Earth-based observer locations, integrating with positionlib for geocentric computations. Finally, projections utilizes the position data to visualize celestial coordinates. This modular design ensures that each component focuses on a specific aspect of astronomical computation, promoting reusability and maintainability.
This is the central component for representing astronomical positions (e.g., Barycentric, Apparent, Astrometric) and performing transformations between various celestial coordinate systems (e.g., ICRF, GCRS). It defines classes like ICRF, Barycentric, and Geocentric which encapsulate position and velocity vectors. It orchestrates coordinate-related operations, including calculating distances, speeds, and converting to right ascension and declination. It imports framelib for rotations and geometry for intersection calculations.
Related Classes/Methods:
Provides functions and classes to generate rotation matrices essential for transforming coordinates between different celestial frames. It defines various reference frames such as ICRS, mean_equator_and_equinox_of_date, true_equator_and_equinox_of_date, tirs, itrs, and ecliptic_frame. These frames are crucial for defining the orientation of coordinate systems at a given time. It serves as a specialized service for rotational mechanics, used by positionlib for coordinate transformations.
Related Classes/Methods:
Represents specific locations on Earth (topocentric coordinates) and handles calculations related to these observer points, such as atmospheric refraction and determining geographic positions. It defines GeographicPosition and Geoid classes, allowing users to specify locations by latitude, longitude, and elevation. It interacts with framelib to obtain Earth-fixed reference frame rotations and provides methods to calculate Local Apparent Sidereal Time (LAST) and refract altitudes.
Related Classes/Methods:
Offers fundamental geometric calculations, such as determining the intersection of a line with a sphere or an ellipsoid. This is crucial for scenarios like occultation checks or general vector mathematics underlying astronomical computations. It provides functions like intersect_line_and_sphere and line_and_ellipsoid_intersection. This component is utilized by positionlib for specific geometric problems.
Related Classes/Methods:
Defines various astronomical projection methods used for mapping celestial coordinates onto a 2D plane, often for charting or visualization purposes. It provides the build_stereographic_projection function, which takes a central point and returns a function to project other positions onto a 2D plane. It acts as a repository of projection algorithms, consuming data from positionlib.
Related Classes/Methods: