# Galactic / Equatorial Coordinate Converter Convert astronomical positions between equatorial (RA/Dec J2000 and B1950), galactic (l/b), and supergalactic (SGL/SGB) coordinate systems. Accurate J2000 IAU 1958 galactic rotation, de Vaucouleurs supergalactic system, and IAU 1976 precession between epochs. Accepts sexagesimal (12h51m26s) or decimal-degree input and shows all four systems for each object. > Canonical page: https://elysiatools.com/en/tools/galactic-coordinate-converter - **Category:** Astronomy - **Keywords:** galactic coordinates, equatorial, right ascension, declination, ra dec, supergalactic, j2000, b1950, precession, celestial, astronomy, coordinate conversion, iau 1958, sgr a ## Overview A coordinate converter for amateur astronomers, astrophotographers, and observers: 1. **From system** — pick the system your input is in: Equatorial J2000 RA/Dec, Equatorial B1950 RA/Dec, Galactic l/b, or Supergalactic SGL/SGB. 2. **To system** — pick the target system (any of the four). 3. **Coordinates** — one object per line. For equatorial, give RA then Dec, e.g. `12 51 26.28 +27 07 41.7` (sexagesimal hours + degrees) or `192.85948 27.12825` (decimal degrees). For galactic/supergalactic, give longitude then latitude in degrees, e.g. `184.56 -5.78`. 4. **Output** — each object is shown in the requested target system, plus an expandable table of all four systems for cross-reference. The galactic conversion uses the modern J2000 realisation of the IAU 1958 system (the same matrix as SIMBAD, Gaia, and NASA/ADS), validated against the Crab Nebula and Sgr A*. Supergalactic coordinates follow de Vaucouleurs et al. (1976). J2000 ↔ B1950 uses the IAU 1976 (Lieske) precession model. All math runs locally. ## Inputs - **Coordinates (one per line)** (textarea): One coordinate per line. For equatorial: RA then Dec. For galactic/supergalactic: longitude then latitude (degrees). - **From system** (select) - **To system** (select) - **Output format** (select) - **Decimal places** (number): Number of decimal places for decimal-degree output. ## When to use - When planning astrophotography sessions or telescope observations that require translating coordinates from star catalogs into galactic coordinates. - When cross-referencing astronomical objects across historical B1950 catalogs and modern J2000 databases. - When analyzing large-scale cosmic structures or galaxy distributions using the supergalactic coordinate system. ## How it works - Select the source coordinate system (Equatorial J2000/B1950, Galactic, or Supergalactic) and your desired target system. - Enter your coordinates in the text area, placing one object per line, using either sexagesimal format (e.g., 12 51 26.28 +27 07 41.7) or decimal degrees. - Configure the output format (Sexagesimal, Decimal degrees, or both) and specify the decimal precision. - The tool processes the coordinates locally using IAU-standard rotation matrices and precession models, instantly displaying the converted values alongside a comprehensive comparison table of all four coordinate systems. ## Use cases - Converting equatorial coordinates of deep-sky targets to galactic coordinates to determine their position relative to the Milky Way plane. - Updating legacy B1950 coordinates from older astronomical papers to modern J2000 coordinates for telescope pointing. - Mapping local galaxy clusters by converting equatorial coordinates to the supergalactic coordinate system. ## Frequently asked questions ### What coordinate systems are supported by this converter? It supports Equatorial J2000, Equatorial B1950, Galactic (l/b), and Supergalactic (SGL/SGB) coordinate systems. ### Can I input multiple coordinates at the same time? Yes, you can input multiple coordinates by entering one object per line in the coordinates text area. ### What formats are accepted for Equatorial coordinates? You can use sexagesimal format (e.g., '05 34 31.94 +22 00 52.2') or decimal degrees (e.g., '192.85948 27.12825'). ### Which mathematical models are used for the conversions? The tool uses the J2000 realization of the IAU 1958 system for galactic coordinates, the de Vaucouleurs (1976) system for supergalactic coordinates, and the IAU 1976 (Lieske) model for precession. ### Are my coordinate inputs sent to an external server? 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