def get_sun_L0(time='now'):
"""
Return the L0 angle for the Sun at a specified time, which is the Carrington longitude of the
Sun-disk center as seen from Earth.
.. warning::
Due to apparent disagreement between published references, the returned L0 may be inaccurate
by up to ~2 arcmin, which translates in the worst case to a shift of ~0.5 arcsec in
helioprojective coordinates for an observer at 1 AU. Until this is resolved, be cautious
with analysis that depends critically on absolute (as opposed to relative) values of
Carrington longitude.
Parameters
----------
time : various
Time to use as `~astropy.time.Time` or in a parse_time-compatible format
Returns
-------
out : `~astropy.coordinates.Longitude`
The Carrington longitude
"""
obstime = _astropy_time(time)
# Calculate the longitude due to the Sun's rotation relative to the stars
# A sidereal rotation is defined to be exactly 25.38 days
sidereal_lon = Longitude(
(obstime.jd - _time_first_rotation.jd) / 25.38 * 360 * u.deg)
# Calculate the longitude of the Earth in de-tilted HCRS
lon_obstime = get_earth(obstime).hcrs.cartesian.transform(_SUN_DETILT_MATRIX) \
.represent_as(SphericalRepresentation).lon.to('deg')
return Longitude(lon_obstime - _lon_first_rotation - sidereal_lon)
def get_sun_L0(time='now'):
"""
Return the L0 angle for the Sun at a specified time, which is the Carrington longitude of the
Sun-disk center as seen from Earth.
.. warning::
Due to apparent disagreement between published references, the returned L0 may be inaccurate
by up to ~2 arcmin, which translates in the worst case to a shift of ~0.5 arcsec in
helioprojective coordinates for an observer at 1 AU. Until this is resolved, be cautious
with analysis that depends critically on absolute (as opposed to relative) values of
Carrington longitude.
Parameters
----------
time : various
Time to use as `~astropy.time.Time` or in a parse_time-compatible format
Returns
-------
out : `~astropy.coordinates.Longitude`
The Carrington longitude
"""
obstime = _astropy_time(time)
# Calculate the longitude due to the Sun's rotation relative to the stars
# A sidereal rotation is defined to be exactly 25.38 days
sidereal_lon = Longitude((obstime.jd - _time_first_rotation.jd) / 25.38 * 360*u.deg)
# Calculate the longitude of the Earth in de-tilted HCRS
lon_obstime = get_earth(obstime).hcrs.cartesian.transform(_SUN_DETILT_MATRIX) \
.represent_as(SphericalRepresentation).lon.to('deg')
return Longitude(lon_obstime - _lon_first_rotation - sidereal_lon)
def get_sun_P(time='now'):
"""
Return the position (P) angle for the Sun at a specified time, which is the angle between
geocentric north and solar north as seen from Earth, measured eastward from geocentric north.
The range of P is +/-26.3 degrees.
Parameters
----------
time : various
Time to use as `~astropy.time.Time` or in a parse_time-compatible format
Returns
-------
out : `~astropy.coordinates.Angle`
The position angle
"""
obstime = _astropy_time(time)
# Define the frame where its Z axis is aligned with geocentric north
geocentric = PrecessedGeocentric(equinox=obstime, obstime=obstime)
return _sun_north_angle_to_z(geocentric)
def get_sun_P(time='now'):
"""
Return the position (P) angle for the Sun at a specified time, which is the angle between
geocentric north and solar north as seen from Earth, measured eastward from geocentric north.
The range of P is +/-26.3 degrees.
Parameters
----------
time : various
Time to use as `~astropy.time.Time` or in a parse_time-compatible format
Returns
-------
out : `~astropy.coordinates.Angle`
The position angle
"""
obstime = _astropy_time(time)
# Define the frame where its Z axis is aligned with geocentric north
geocentric = PrecessedGeocentric(equinox=obstime, obstime=obstime)
return _sun_north_angle_to_z(geocentric)
def get_body_heliographic_stonyhurst(body, time='now'):
"""
Return a `~sunpy.coordinates.frames.HeliographicStonyhurst` frame for the location of a
solar-system body at a specified time.
Parameters
----------
body : `str`
The solar-system body for which to calculate positions
time : various
Time to use as `~astropy.time.Time` or in a parse_time-compatible format
Returns
-------
out : `~sunpy.coordinates.frames.HeliographicStonyhurst`
Location of the solar-system body in the `~sunpy.coordinates.HeliographicStonyhurst` frame
"""
obstime = _astropy_time(time)
body_icrs = ICRS(get_body_barycentric(body, obstime))
body_hgs = body_icrs.transform_to(HGS(obstime=obstime))
return body_hgs
def get_body_heliographic_stonyhurst(body, time='now'):
"""
Return a `~sunpy.coordinates.frames.HeliographicStonyhurst` frame for the location of a
solar-system body at a specified time.
Parameters
----------
body : `str`
The solar-system body for which to calculate positions
time : various
Time to use as `~astropy.time.Time` or in a parse_time-compatible format
Returns
-------
out : `~sunpy.coordinates.frames.HeliographicStonyhurst`
Location of the solar-system body in the `~sunpy.coordinates.HeliographicStonyhurst` frame
"""
obstime = _astropy_time(time)
body_icrs = ICRS(get_body_barycentric(body, obstime))
body_hgs = body_icrs.transform_to(HGS(obstime=obstime))
return body_hgs
def get_sun_orientation(location, time='now'):
"""
Return the orientation angle for the Sun from a specified Earth location and time. The
orientation angle is the angle between local zenith and solar north, measured eastward from
local zenith.
Parameters
----------
location : `~astropy.coordinates.EarthLocation`
Observer location on Earth
time : various
Time to use as `~astropy.time.Time` or in a parse_time-compatible format
Returns
-------
out : `~astropy.coordinates.Angle`
The orientation of the Sun
"""
obstime = _astropy_time(time)
# Define the frame where its Z axis is aligned with local zenith
local_frame = AltAz(obstime=obstime, location=location)
return _sun_north_angle_to_z(local_frame)
def get_sun_orientation(location, time='now'):
"""
Return the orientation angle for the Sun from a specified Earth location and time. The
orientation angle is the angle between local zenith and solar north, measured eastward from
local zenith.
Parameters
----------
location : `~astropy.coordinates.EarthLocation`
Observer location on Earth
time : various
Time to use as `~astropy.time.Time` or in a parse_time-compatible format
Returns
-------
out : `~astropy.coordinates.Angle`
The orientation of the Sun
"""
obstime = _astropy_time(time)
# Define the frame where its Z axis is aligned with local zenith
local_frame = AltAz(obstime=obstime, location=location)
return _sun_north_angle_to_z(local_frame)