cdshealpix.ring.healpix_to_lonlat¶
- cdshealpix.ring.healpix_to_lonlat(ipix, nside, dx=0.5, dy=0.5, num_threads=0)¶
Get the longitudes and latitudes of the center of some HEALPix cells at a given depth.
This method does the opposite transformation of
lonlat_to_healpix. It’s wrapped around the center method from the cdshealpix Rust crate.- Parameters:
- ipix
numpy.ndarray The HEALPix cell indexes given as a
np.uint64numpy array.- nside
numpy.ndarray The nside of the HEALPix cells.
- dxfloat, optional
The offset position \(\in [0, 1]\) along the X axis. By default,
dx=0.5- dyfloat, optional
The offset position \(\in [0, 1]\) along the Y axis. By default,
dy=0.5- num_threadsint, optional
Specifies the number of threads to use for the computation. Default to 0 means it will choose the number of threads based on the RAYON_NUM_THREADS environment variable (if set), or the number of logical CPUs (otherwise)
- ipix
- Returns:
- lon, lat(
astropy.coordinates.Longitude,astropy.coordinates.Latitude) The sky coordinates of the center of the HEALPix cells given as a longitude, latitude tuple.
- lon, lat(
- Raises:
- ValueError
When the HEALPix cell indexes given have values out of \([0, 12\) x \(N_{side} ^ 2[\).
Examples
>>> from cdshealpix.ring import healpix_to_lonlat >>> import numpy as np >>> ipix = np.array([42, 6, 10], dtype=np.uint64) >>> depth = np.array([2, 12]) >>> nside = 2 ** depth >>> lon, lat = healpix_to_lonlat(ipix[:, np.newaxis], nside[np.newaxis, :])