def rectangular_coordinates_b1950(epoch):
"""This method computes the rectangular geocentric equatorial
coordinates (X, Y, Z) of the Sun, referred to the mean equinox of
B1950.0. The X axis is directed towards the vernal equinox (longitude
0), the Y axis lies in the plane of the equator and is directed towards
longitude 90, and the Z axis is directed towards the north celestial
pole.
:param epoch: Epoch to compute Sun position, as an Epoch object
:type epoch: :py:class:`Epoch`
:returns: A tuple with the X, Y, Z values in astronomical units
:rtype: tuple
:raises: TypeError if input values are of wrong type.
>>> epoch = Epoch(1992, 10, 13.0)
>>> x, y, z = Sun.rectangular_coordinates_b1950(epoch)
>>> print(round(x, 8))
-0.94149557
>>> print(round(y, 8))
-0.30259922
>>> print(round(z, 8))
-0.11578695
"""
# First check that input values are of correct types
if not isinstance(epoch, Epoch):
raise TypeError("Invalid input type")
# Second, compute Earth heliocentric position referred to J2000.0
lon, lat, r = Earth.geometric_heliocentric_position_j2000(epoch)
# Third, convert from Earth's heliocentric to Sun's geocentric
lon = lon.to_positive() + 180.0
lat = -lat
x = r * cos(lat.rad()) * cos(lon.rad())
y = r * cos(lat.rad()) * sin(lon.rad())
z = r * sin(lat.rad())
x = 0.999925702634 * x + 0.012189716217 * y + 0.000011134016 * z
y = -0.011179418036 * x + 0.917413998946 * y - 0.397777041885 * z
z = -0.004859003787 * x + 0.397747363646 * y + 0.917482111428 * z
return x, y, z
def rectangular_coordinates_j2000(epoch):
"""This method computes the rectangular geocentric equatorial
coordinates (X, Y, Z) of the Sun, referred to the standard equinox of
J2000.0. The X axis is directed towards the vernal equinox (longitude
0), the Y axis lies in the plane of the equator and is directed towards
longitude 90, and the Z axis is directed towards the north celestial
pole.
:param epoch: Epoch to compute Sun position, as an Epoch object
:type epoch: :py:class:`Epoch`
:returns: A tuple with the X, Y, Z values in astronomical units
:rtype: tuple
:raises: TypeError if input values are of wrong type.
>>> epoch = Epoch(1992, 10, 13.0)
>>> x, y, z = Sun.rectangular_coordinates_j2000(epoch)
>>> print(round(x, 8))
-0.93740485
>>> print(round(y, 8))
-0.3131474
>>> print(round(z, 8))
-0.13577045
"""
# First check that input values are of correct types
if not isinstance(epoch, Epoch):
raise TypeError("Invalid input type")
# Second, compute Earth heliocentric position referred to J2000.0
lon, lat, r = Earth.geometric_heliocentric_position_j2000(epoch)
# Third, convert from Earth's heliocentric to Sun's geocentric
lon = lon.to_positive() + 180.0
lat = -lat
x = r * cos(lat.rad()) * cos(lon.rad())
y = r * cos(lat.rad()) * sin(lon.rad())
z = r * sin(lat.rad())
x0 = x + 0.00000044036 * y - 0.000000190919 * z
y0 = -0.000000479966 * x + 0.917482137087 * y - 0.397776982902 * z
z0 = 0.397776982902 * y + 0.917482137087 * z
return x0, y0, z0