Sun

Module holding functions to handle coordinates.

class pymeeus.Sun.Sun

Class Sun handles the parameters related to the Sun.

__init__()

Sun constructor.

Returns:Sun object. Return type:Sun

__weakref__

list of weak references to the object (if defined)

static apparent_geocentric_position(epoch, nutation=True)

This method computes the apparent geocentric position of the Sun for a given epoch, using the VSOP87 theory.

Parameters:

• epoch (bool) – Epoch to compute Sun position, as an Epoch object
• nutation – Whether the nutation correction will be applied

Returns:

A tuple with the heliocentric longitude and latitude (as Angle objects), and the radius vector (as a float, in astronomical units), in that order

Return type:

tuple

Raises:

TypeError if input values are of wrong type.

>>> epoch = Epoch(1992, 10, 13.0)
>>> lon, lat, r = Sun.apparent_geocentric_position(epoch)
>>> print(lon.to_positive().dms_str(n_dec=3))
199d 54' 21.548''
>>> print(lat.dms_str(n_dec=3))
0.721''
>>> print(round(r, 8))
0.99760852

static apparent_longitude_coarse(epoch)

This method provides the Sun’s apparent longitude with a relatively low accuracy of about 0.01 degree.

Parameters:epoch (Epoch) – Epoch to compute the position of the Sun Returns:A tuple containing the sun_apparent (ecliptical) longitude (as an Angle object) and the radius vector in astronomical units. Return type:tuple Raises:TypeError if input value is of wrong type.

>>> epoch = Epoch(1992, 10, 13)
>>> app_lon, r = Sun.apparent_longitude_coarse(epoch)
>>> print(app_lon.dms_str(n_dec=0))
199d 54' 32.0''
>>> print(round(r, 5))
0.99766

static apparent_rightascension_declination_coarse(epoch)

This method provides the Sun’s apparent right ascension and declination with a relatively low accuracy of about 0.01 degree.

Parameters:epoch (Epoch) – Epoch to compute the position of the Sun Returns:A tuple containing the right ascension and the declination (as Angle objects) and the radius vector in astronomical units. Return type:tuple Raises:TypeError if input value is of wrong type.

>>> epo = Epoch(1992, 10, 13)
>>> ra, delta, r = Sun.apparent_rightascension_declination_coarse(epo)
>>> print(ra.ra_str(n_dec=1))
13h 13' 31.4''
>>> print(delta.dms_str(n_dec=0))
-7d 47' 6.0''
>>> print(round(r, 5))
0.99766

static beginning_synodic_rotation(number)

This method calculates the epoch when the Carrington’s synodic rotation No. ‘number’ starts.

Parameters:number (int) – Number of Carrington’s synodic rotation Returns:Epoch when the provided rotation starts Return type:Epoch Raises:TypeError if input value is of wrong type.

>>> epoch = Sun.beginning_synodic_rotation(1699)
>>> print(round(epoch(), 3))
2444480.723

static ephemeris_physical_observations(epoch)

This method uses Carrington’s formulas to compute the following quantities:

• P : position angle of the northern extremity of the axis of rotation
• B0 : heliographic latitude of the center of the solar disk
• L0 : heliographic longitude of the center of the solar disk

Parameters:epoch (Epoch) – Epoch to compute the parameters Returns:Parameters P, B0 and L0, in a tuple Return type:tuple Raises:TypeError if input value is of wrong type.

>>> epoch = Epoch(1992, 10, 13)
>>> p, b0, l0 = Sun.ephemeris_physical_observations(epoch)
>>> print(round(p, 2))
26.27
>>> print(round(b0, 2))
5.99
>>> print(round(l0, 2))
238.63

static equation_of_time(epoch)

This method computes the equation of time for a given epoch, understood as the difference between apparent and mean time, or the difference between the hour angle of the true Sun and the mean Sun.

Parameters:epoch (Epoch) – Epoch to compute the equation of time, as an Epoch object Returns:Difference between apparent and mean time, as a tuple, in minutes (int) and seconds (float) of time Return type:tuple Raises:TypeError if input values are of wrong type.

>>> epoch = Epoch(1992, 10, 13.0)
>>> m, s = Sun.equation_of_time(epoch)
>>> print(m)
13
>>> print(round(s, 1))
42.6

static geometric_geocentric_position(epoch, tofk5=True)

This method computes the geometric geocentric position of the Sun for a given epoch, using the VSOP87 theory.

Parameters:

• epoch (Epoch) – Epoch to compute Sun position, as an Epoch object
• tofk5 (bool) – Whether or not the small correction to convert to the FK5 system will be applied or not

Returns:

A tuple with the geocentric longitude and latitude (as Angle objects), and the radius vector (as a float, in astronomical units), in that order

Return type:

tuple

Raises:

TypeError if input values are of wrong type.

>>> epoch = Epoch(1992, 10, 13.0)
>>> l, b, r = Sun.geometric_geocentric_position(epoch, tofk5=False)
>>> print(round(l.to_positive(), 6))
199.907297
>>> print(b.dms_str(n_dec=3))
0.744''
>>> print(round(r, 8))
0.99760852

static get_equinox_solstice(year, target='spring')

This method computes the times of the equinoxes or the solstices.

Parameters:

• year (int) – Year we want to compute the equinox or solstice for
• target (str) – Corresponding equinox or solstice. It can be “spring”, “summer”, “autumn”, “winter”

Returns:

The instant of time when the equinox or solstice happens

Return type:

Epoch

Raises:

TypeError if input values are of wrong type.

Raises:

ValueError if ‘target’ value is invalid.

>>> epoch = Sun.get_equinox_solstice(1962, target="summer")
>>> y, m, d, h, mi, s = epoch.get_full_date()
>>> print("{}/{}/{} {}:{}:{}".format(y, m, d, h, mi, round(s, 0)))
1962/6/21 21:24:42.0

static 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.

Parameters:epoch (Epoch) – Epoch to compute Sun position, as an Epoch object Returns:A tuple with the X, Y, Z values in astronomical units Return type: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

static rectangular_coordinates_equinox(epoch, equinox_epoch)

This method computes the rectangular geocentric equatorial coordinates (X, Y, Z) of the Sun, referred to an arbitrary mean equinox. 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.

Parameters:

• epoch (Epoch) – Epoch to compute Sun position, as an Epoch object
• equinox_epoch (Epoch) – Epoch corresponding to the mean equinox

Returns:

A tuple with the X, Y, Z values in astronomical units

Return type:

tuple

Raises:

TypeError if input values are of wrong type.

>>> epoch = Epoch(1992, 10, 13.0)
>>> e_equinox = Epoch(2467616.0)
>>> x, y, z = Sun.rectangular_coordinates_equinox(epoch, e_equinox)
>>> print(round(x, 8))
-0.93368986
>>> print(round(y, 8))
-0.32235085
>>> print(round(z, 8))
-0.13977098

static 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.

Parameters:epoch (Epoch) – Epoch to compute Sun position, as an Epoch object Returns:A tuple with the X, Y, Z values in astronomical units Return type: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

static rectangular_coordinates_mean_equinox(epoch)

This method computes the rectangular geocentric equatorial coordinates (X, Y, Z) of the Sun, referred to the mean equinox of the date. 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.

Parameters:epoch (Epoch) – Epoch to compute Sun position, as an Epoch object Returns:A tuple with the X, Y, Z values in astronomical units Return type:tuple Raises:TypeError if input values are of wrong type.

>>> epoch = Epoch(1992, 10, 13.0)
>>> x, y, z = Sun.rectangular_coordinates_mean_equinox(epoch)
>>> print(round(x, 7))
-0.9379963
>>> print(round(y, 6))
-0.311654
>>> print(round(z, 7))
-0.1351207

static true_longitude_coarse(epoch)

This method provides the Sun’s true longitude with a relatively low accuracy of about 0.01 degree.

Parameters:epoch (Epoch) – Epoch to compute the position of the Sun Returns:A tuple containing the true (ecliptical) longitude (as an Angle object) and the radius vector in astronomical units. Return type:tuple Raises:TypeError if input value is of wrong type.

>>> epoch = Epoch(1992, 10, 13)
>>> true_lon, r = Sun.true_longitude_coarse(epoch)
>>> print(true_lon.dms_str(n_dec=0))
199d 54' 36.0''
>>> print(round(r, 5))
0.99766