def add_offset(self, da_cosdec, ddec):
""" Adds an offset to the star position
Parameters:
da_cosdec (int, float): offset in Delta_alpha_cos_delta in mas
ddec (int, float): offset in Delta_delta in mas
"""
dadc = test_attr(da_cosdec, float, 'da_cosdec')
dd = test_attr(ddec, float, 'ddec')
self.offset = SphericalCosLatDifferential(dadc * u.mas, dd * u.mas,
0.0 * u.km)
def get_ksi_eta(self, time, star):
""" Calculates relative position to star in the orthographic projection.
Parameters:
time (str, Time): Reference time to calculate the position.
It can be a string in the format "yyyy-mm-dd hh:mm:ss.s" or an astropy Time object
star (str, SkyCoord): The coordinate of the star in the same reference frame as the ephemeris.
It can be a string in the format "hh mm ss.s +dd mm ss.ss"
or an astropy SkyCoord object.
Returns:
ksi, eta (float): on-sky orthographic projection of the observer relative to a star
Ksi is in the North-South direction (North positive)
Eta is in the East-West direction (East positive)
"""
time = test_attr(time, Time, 'time')
try:
star = SkyCoord(star, unit=(u.hourangle, u.deg))
except:
raise ValueError(
'star is not an astropy object or a string in the format "hh mm ss.s +dd mm ss.ss"'
)
itrs = self.site.get_itrs(obstime=time)
gcrs = itrs.transform_to(GCRS(obstime=time))
rz = rotation_matrix(star.ra, 'z')
ry = rotation_matrix(-star.dec, 'y')
cp = gcrs.cartesian.transform(rz).transform(ry)
return cp.y.to(u.km).value, cp.z.to(u.km).value
def __init__(self, **kwargs):
""" Defines the observer object
Parameters:
name (str): Name for the Observer. (required)
Observer is uniquely defined (name must be different for each observer).
code (str): The IAU code for SORA to search for its coordinates in MPC database
site (EarthLocation): User provides an EarthLocation object.
lon (str, float): The Longitude of the site in degrees.
Positive to East. Range (0 to 360) or (-180 to +180)
User can provide in degrees (float) or hexadecimal (string)
lat (str, float): The Latitude of the site in degrees.
Positive North. Range (+90 to -90)
User can provide in degrees (float) or hexadecimal (string)
height (int, float): The height of the site in meters above see level.
Examples:
User can provide one of the following to define an observer:
- If user will use the MPC name for the site:
Observer(code)
- If user wants to use a different name from the MPC database:
Observer(name, code)
- If user wants to use an EarthLocation value:
EarthLocation(lon, lat, height)
Observer(name, site)
- If user wants to give site coordinates directly:
Observer(name, lon, lat, height)
"""
input_tests.check_kwargs(
kwargs,
allowed_kwargs=['code', 'height', 'lat', 'lon', 'name', 'site'])
if 'code' in kwargs:
self.code = kwargs['code']
try:
name, self.site = search_code_mpc()[self.code]
self.__name = kwargs.get('name', name)
except:
raise ValueError(
'code {} could not be located in MPC database'.format(
self.code))
elif all(i in kwargs for i in ['name', 'site']):
self.__name = kwargs['name']
self.site = test_attr(kwargs['site'], EarthLocation, 'site')
elif all(i in kwargs for i in ['name', 'lon', 'lat', 'height']):
self.__name = kwargs['name']
self.site = EarthLocation(kwargs['lon'], kwargs['lat'],
kwargs['height'])
else:
raise ValueError('Input parameters could not be determined')
if self.__name in self.__names:
raise ValueError(
"name {} already defined for another Observer object. "
"Please choose a different one.".format(self.__name))
self.__names.append(self.__name)
def altaz(self, time, coord):
""" Calculates the Altitude and Azimuth at a reference time for a coordinate
Parameters:
time (str,Time): Reference time to calculate the sidereal time.
coord (str, astropy.SkyCoord): Coordinate of the target ICRS.
Returns:
altitude (float): object altitude in degrees.
azimuth (float): object azimuth in degrees.
"""
time = test_attr(time, Time, 'time')
if type(coord) == str:
coord = SkyCoord(coord, unit=(u.hourangle, u.deg))
ephem_altaz = coord.transform_to(
AltAz(obstime=time, location=self.site))
return ephem_altaz.alt.deg, ephem_altaz.az.deg
def set_magnitude(self, **kwargs):
""" Sets the magnitudes of a star.
Parameters:
(band name)=(float): The star magnitude for given band. The band name can be any string the user wants.
Examples:
set_magnitude(G=10)
set_magnitude(K=15)
set_magnitude(newband=6)
"""
for key in kwargs:
mag = test_attr(kwargs[key], float, key)
if key in self.mag:
warnings.warn(
'{0} mag already defined. {0}={1} will be replaced by {0}={2}'
.format(key, self.mag[key], mag))
self.mag[key] = mag
def sidereal_time(self, time, mode='local'):
""" Calculates the Apparent Sidereal Time at a reference time
Parameters:
time (str,Time): Reference time to calculate sidereal time.
mode (str): local or greenwich
If 'local': calculates the sidereal time for the coordinates of this object.
If 'greenwich': calculates the Greenwich Apparent Sidereal Time.
Returns:
sidereal_time: An Astropy Longitude object with the Sidereal Time.
"""
# return local or greenwich sidereal time
time = test_attr(time, Time, 'time')
time.location = self.site
if mode == 'local':
return time.sidereal_time('apparent')
elif mode == 'greenwich':
return time.sidereal_time('apparent', 'greenwich')
else:
raise ValueError('mode must be "local" or "greenwich"')