Table of Contents
Converter
Galactic latitude (b) | Galactic longitude (\(l\)) | |
---|---|---|
RA (dd) | Dec (dd) | |
Fromula
To convert from galactic to equatorial coordinates,
\small \begin{equation} \sin(\delta) = \sin(\delta_\text{NGP})\sin(b)+ \cos(\delta_\text{NGP})\cos(b)\cos(l_\text{NCP} - l) \end{equation}
\small \begin{equation} \tan(\alpha - \alpha_\text{NGP}) = \frac{\cos(b)\sin(l_\text{NCP} - l)}{\cos(\delta_\text{NGP})\sin(b) - \sin(\delta_\text{NGP})\cos(b)\cos(l_\text{NCP} - l)} \end{equation}
According to IAU, the values of $l_\text{NCP}$, $\delta_\text{NGP}$, and $\alpha_\text{NGP}$ are $122.9320^\circ$, $27.1284^\circ$, and $192.8595^\circ$ respectively.
Galactic coordinates
- Independant of the observer’s location and time of observation.
- Heliocenteric, the galactic plane is the fundamental plane for the galactic coordinate system.
- Primary direction is towards the center of Milky Way galaxy.
- It is a right-handed coordinate system, positive towards North and East direction.
Equatorial coordinates
- Indepdendant of the observer’s location and time of observation.
- Earth centeric, the equator of Earth is the fundamental plane for the equatorial coordinate system.
- Primary direction is towards the vernal equinox.
- It is a right-handed coordinate system, positive towards North and East direction.
See more
For python codes to convert galactic to equatorial coordiantes, see the post “How to interconvert celestial coordinate systems?#Equatorial_Galactic”.