def test_angular_separation(self):
time = sunset_and_rise_for_date(self.data, 2020, 12, 17)[0]
moon = self.data.ephemeris['moon']
mercury = self.data.get_body("Mercury")
sep, pos = angular_separation(self.data, moon, mercury, time)
self.assertLessEqual(abs(sep.degrees - 39.1), 1.0)
self.assertEqual(pos, EclipticPosition.BEHIND)
sep, pos = angular_separation(self.data, mercury, moon, time)
self.assertEqual(pos, EclipticPosition.AHEAD)
self.assertLessEqual(abs(sep.degrees - 39.1), 1.0)
dablin = Star.from_dataframe(self.data.stars.loc[100345])
sep, pos = angular_separation(self.data, moon, dablin, time)
self.assertEqual(pos, EclipticPosition.BELOW)
self.assertLessEqual(abs(sep.degrees - 8.9), 1.0)
sep, pos = angular_separation(self.data, dablin, moon, time)
self.assertEqual(pos, EclipticPosition.ABOVE)
self.assertLessEqual(abs(sep.degrees - 8.9), 1.0)
fomalhaut = Star.from_dataframe(self.data.stars.loc[113368])
sep, pos = angular_separation(self.data, fomalhaut, mercury, time)
self.assertEqual(pos, EclipticPosition.BEHIND)
self.assertLessEqual(abs(sep.degrees - 70.45), 1.0)
sep, pos = angular_separation(self.data, mercury, fomalhaut, time)
self.assertEqual(pos, EclipticPosition.AHEAD)
self.assertLessEqual(abs(sep.degrees - 70.45), 1.0)
def parse(line):
"""Return a `Star` build by parsing a Hipparcos catalog entry `line`."""
# See ftp://cdsarc.u-strasbg.fr/cats/I/239/ReadMe
star = Star(
ra=Angle(degrees=float(line[51:63])),
dec=Angle(degrees=float(line[64:76])),
ra_mas_per_year=float(line[87:95]),
dec_mas_per_year=float(line[96:104]),
parallax_mas=float(line[79:86]),
names=[('HIP', int(line[8:14]))],
)
star._position_au += star._velocity_au_per_d * days
distance, dec, ra = to_polar(star._position_au)
star.ra = Angle(radians=ra, preference='hours')
star.dec = Angle(radians=dec)
return star
def test_cirs_sofa():
ts = api.load.timescale()
earth = api.load('de421.bsp')['earth']
test_data = [
[45.0, 46.0, 2458327],
[200.0, -22.0, 2458327],
[45.0, 46.0, 2459327]
]
# Results output by SOFA. Calculated using the source code above.
sofa_results = [
[45.074343838325, 46.067831092355],
[200.013551320030, -22.096008994214],
[45.077698288877, 46.082296559677]
]
tol = 1e-5 / 3600.0 # 10 micro arc-seconds
for ((ra_icrs, dec_icrs, tdb), (ra_sofa, dec_sofa)) in zip(test_data, sofa_results):
ss = Star(ra_hours=(ra_icrs / 15.0), dec_degrees=dec_icrs)
st = ts.tdb(jd=tdb)
with low_precision_ERA():
ra_cirs, dec_cirs, _ = earth.at(st).observe(ss).apparent().cirs_radec(st)
assert np.allclose(ra_cirs._degrees, ra_sofa, rtol=0.0, atol=tol)
assert np.allclose(dec_cirs._degrees, dec_sofa, rtol=0.0, atol=tol)
def parse(line):
"DEPRECATED; see :func:`~skyfield.data.hipparcos.load_dataframe() instead."
# See ftp://cdsarc.u-strasbg.fr/cats/I/239/ReadMe
star = Star(
ra=Angle(degrees=float(line[51:63])),
dec=Angle(degrees=float(line[64:76])),
ra_mas_per_year=float(line[87:95]),
dec_mas_per_year=float(line[96:104]),
parallax_mas=float(line[79:86]),
names=[('HIP', int(line[8:14]))],
)
star._position_au += star._velocity_au_per_d * days
distance, dec, ra = to_polar(star._position_au)
star.ra = Angle(radians=ra, preference='hours')
star.dec = Angle(radians=dec)
return star
def run(location, t, target):
"""
Assumes location is dict with "latitude", "longitude" keys in decimal degres, and "elevation" key in meters
Assumes t is datetime obj
Assumes target is astropy SkyCoord with ICRS RA and DE
"""
planets = load("de421.bsp")
earth = planets["earth"]
moon = planets["moon"]
# convert from astropy SkyCoord to skyfield "Star"
target = Star(ra_hours=target.ra.hour, dec_degrees=target.dec.degree)
loc = earth + Topos(location["latitude"],
location["longitude"],
elevation_m=location["elevation"])
moon_app_pos = loc.at(t).observe(moon).apparent()
app_pos = loc.at(t).observe(target).apparent()
alt, _, _ = app_pos.altaz()
alt = alt.degrees # convert from skyfield.units.Angle to float degrees
moondiff = moon_app_pos.separation_from(app_pos).degrees
return alt, moondiff
def parse(line):
"DEPRECATED; see :func:`~skyfield.data.hipparcos.load_dataframe() instead."
# See ftp://cdsarc.u-strasbg.fr/cats/I/239/ReadMe
star = Star(
ra=Angle(degrees=float(line[51:63])),
dec=Angle(degrees=float(line[64:76])),
ra_mas_per_year=float(line[87:95]),
dec_mas_per_year=float(line[96:104]),
parallax_mas=float(line[79:86]),
names=[('HIP', int(line[8:14]))],
)
star._position_au += star._velocity_au_per_d * days
distance, dec, ra = to_polar(star._position_au)
star.ra = Angle(radians=ra, preference='hours')
star.dec = Angle(radians=dec)
return star
def parse(line):
"""Return a `Star` build by parsing a Hipparcos catalog entry `line`."""
# See ftp://cdsarc.u-strasbg.fr/cats/I/239/ReadMe
star = Star(
ra=Angle(degrees=float(line[51:63])),
dec=Angle(degrees=float(line[64:76])),
ra_mas_per_year=float(line[87:95]),
dec_mas_per_year=float(line[96:104]),
parallax_mas=float(line[79:86]),
names=[('HIP', int(line[8:14]))],
)
star._position_au += star._velocity_au_per_d * days
distance, dec, ra = to_polar(star._position_au)
star.ra = Angle(radians=ra, preference='hours')
star.dec = Angle(radians=dec)
return star
def star(self,
ref: Union[str, int],
culture: Optional[str] = None) -> CelestialObject:
"""Fetch a star by its name or Hipparcos catalogue number.
Args:
ref: Either the string common name, or the int catalogue number, e.g. 87937 for
Barnard's Star.
culture: If given, use as a hint to understand the common name.
"""
number = ref if isinstance(ref, int) else self.starNumber(ref)
data = self._stars.loc[number]
names = self._starNames.allNames(number)
primaryName = (ref if isinstance(ref, str) else names["western"]
if "western" in names else names["hip"])
star = Star.from_dataframe(data)
return makeObject(
type=ObjectType.STAR,
name=primaryName,
position=star,
dataFrame=data,
names=names,
)
def get_body(self, name: str):
name = name.lower()
if name == MERCURY.name:
return self.ephemeris["MERCURY BARYCENTER"]
if name == VENUS.name:
return self.ephemeris["VENUS BARYCENTER"]
if name == EARTH:
return self.ephemeris["EARTH"]
if name == MARS.name:
return self.ephemeris["MARS BARYCENTER"]
if name == SATURN.name:
return self.ephemeris["SATURN BARYCENTER"]
if name == JUPITER.name:
return self.ephemeris["JUPITER BARYCENTER"]
if name == MOON:
return self.ephemeris["MOON"]
if name == SUN:
return self.ephemeris["SUN"]
if name == ALCYONE:
return Star.from_dataframe(self.stars.loc[17702])
if name == ANTARES:
return Star.from_dataframe(self.stars.loc[80763])
if name == BETA_CAPRICORNI:
return Star.from_dataframe(self.stars.loc[100345])
if name == BETA_GEMINORUM:
return Star.from_dataframe(self.stars.loc[37826])
if name == BETA_LIBRAE:
return Star.from_dataframe(self.stars.loc[74785])
if name == BETA_VIRGINIS:
return Star.from_dataframe(self.stars.loc[57757])
if name == EPSILON_LEONIS:
return Star.from_dataframe(self.stars.loc[47908])
if name == EPSILON_PISCIUM:
return Star.from_dataframe(self.stars.loc[4906])
if name == FORTY_TWO_CANCRI:
return Star.from_dataframe(self.stars.loc[42578])
if name == REGULUS:
return Star.from_dataframe(self.stars.loc[49669])
if name == THETA_LEONIS:
return Star.from_dataframe(self.stars.loc[54879])
if name == SHERATAN:
return Star.from_dataframe(self.stars.loc[8903])
if name == NU_ARIETIS:
return Star.from_dataframe(self.stars.loc[12332])
if name == NU_AURIGAE:
return Star.from_dataframe(self.stars.loc[27673])
if name == THETA_CANCRI:
return Star.from_dataframe(self.stars.loc[41822])
if name == ETA_CAPRICORNI:
return Star.from_dataframe(self.stars.loc[104019])
if name == OMEGA_GEMINORUM:
return Star.from_dataframe(self.stars.loc[33927])
if name == FIFTY_TWO_LEONIS:
return Star.from_dataframe(self.stars.loc[52689])
if name == NU_LIBRAE:
return Star.from_dataframe(self.stars.loc[73945])
if name == THIRTY_SIX_PERSEI:
return Star.from_dataframe(self.stars.loc[16499])
if name == FIFTY_EIGHT_PISCIUM:
return Star.from_dataframe(self.stars.loc[3675])
if name == ASCELLA:
return Star.from_dataframe(self.stars.loc[93506])
if name == EPSILON_TAURI:
return Star.from_dataframe(self.stars.loc[20889])
if name == THETA_VIRGINIS:
return Star.from_dataframe(self.stars.loc[64238])
raise ValueError