Source code for ctapipe.utils.astro

# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""
This module is intended to contain astronomy-related helper tools which are
not provided by external packages and/or to satisfy particular needs of
usage within ctapipe.
"""
from astropy.coordinates import Angle
from astropy.coordinates import SkyCoord
from astropy import units as u

__all__ = ["get_bright_stars"]


[docs]def get_bright_stars(pointing=None, radius=None, magnitude_cut=None): """ Returns an astropy table containing star positions above a given magnitude within a given radius around a position in the sky, using the Yale bright star catalog which needs to be present in the ctapipe-extra package. The included Yale bright star catalog contains all 9096 stars, excluding the Nova objects present in the original catalog from Hoffleit & Jaschek (1991), http://adsabs.harvard.edu/abs/1991bsc..book.....H, and is complete down to magnitude ~6.5, while the faintest included star has mag=7.96. Parameters ---------- pointing: astropy Skycoord pointing direction in the sky (if none is given, full sky is returned) radius: astropy angular units Radius of the sky region around pointing position. Default: full sky magnitude_cut: float Return only stars above a given magnitude. Default: None (all entries) Returns ------- Astropy table: List of all stars after cuts with names, catalog numbers, magnitudes, and coordinates """ from ctapipe.utils import get_table_dataset catalog = get_table_dataset("yale_bright_star_catalog5", role="bright star catalog") starpositions = SkyCoord( ra=Angle(catalog["RAJ2000"], unit=u.deg), dec=Angle(catalog["DEJ2000"], unit=u.deg), frame="icrs", copy=False, ) catalog["ra_dec"] = starpositions if magnitude_cut is not None: catalog = catalog[catalog["Vmag"] < magnitude_cut] if radius is not None: if pointing is None: raise ValueError( "Sky pointing, pointing=SkyCoord(), must be " "provided if radius is given." ) separations = catalog["ra_dec"].separation(pointing) catalog["separation"] = separations catalog = catalog[separations < radius] catalog.remove_columns(["RAJ2000", "DEJ2000"]) return catalog