def fk4_to_fk4_no_e(fk4coord, fk4noeframe):
# Extract cartesian vector
rep = fk4coord.cartesian
# Find distance (for re-normalization)
d_orig = rep.norm()
rep /= d_orig
# Apply E-terms of aberration. Note that this depends on the equinox (not
# the observing time/epoch) of the coordinates. See issue #1496 for a
# discussion of this.
eterms_a = CartesianRepresentation(
u.Quantity(fk4_e_terms(fk4coord.equinox), u.dimensionless_unscaled,
copy=False), copy=False)
rep = rep - eterms_a + eterms_a.dot(rep) * rep
# Find new distance (for re-normalization)
d_new = rep.norm()
# Renormalize
rep *= d_orig / d_new
# now re-cast into an appropriate Representation, and precess if need be
if isinstance(fk4coord.data, UnitSphericalRepresentation):
rep = rep.represent_as(UnitSphericalRepresentation)
# if no obstime was given in the new frame, use the old one for consistency
newobstime = fk4coord._obstime if fk4noeframe._obstime is None else fk4noeframe._obstime
fk4noe = FK4NoETerms(rep, equinox=fk4coord.equinox, obstime=newobstime)
if fk4coord.equinox != fk4noeframe.equinox:
# precession
fk4noe = fk4noe.transform_to(fk4noeframe)
return fk4noe
def fk4_no_e_to_fk4(fk4noecoord, fk4frame):
# first precess, if necessary
if fk4noecoord.equinox != fk4frame.equinox:
fk4noe_w_fk4equinox = FK4NoETerms(equinox=fk4frame.equinox,
obstime=fk4noecoord.obstime)
fk4noecoord = fk4noecoord.transform_to(fk4noe_w_fk4equinox)
# Extract cartesian vector
rep = fk4noecoord.cartesian
# Find distance (for re-normalization)
d_orig = rep.norm()
rep /= d_orig
# Apply E-terms of aberration. Note that this depends on the equinox (not
# the observing time/epoch) of the coordinates. See issue #1496 for a
# discussion of this.
eterms_a = CartesianRepresentation(u.Quantity(fk4_e_terms(
fk4noecoord.equinox),
u.dimensionless_unscaled,
copy=False),
copy=False)
rep0 = rep.copy()
for _ in range(10):
rep = (eterms_a + rep0) / (1. + eterms_a.dot(rep))
# Find new distance (for re-normalization)
d_new = rep.norm()
# Renormalize
rep *= d_orig / d_new
# now re-cast into an appropriate Representation, and precess if need be
if isinstance(fk4noecoord.data, UnitSphericalRepresentation):
rep = rep.represent_as(UnitSphericalRepresentation)
return fk4frame.realize_frame(rep)
def fk4_no_e_to_fk4(fk4noecoord, fk4frame):
# first precess, if necessary
if fk4noecoord.equinox != fk4frame.equinox:
fk4noe_w_fk4equinox = FK4NoETerms(equinox=fk4frame.equinox,
obstime=fk4noecoord.obstime)
fk4noecoord = fk4noecoord.transform_to(fk4noe_w_fk4equinox)
# Extract cartesian vector
rep = fk4noecoord.cartesian
# Find distance (for re-normalization)
d_orig = rep.norm()
rep /= d_orig
# Apply E-terms of aberration. Note that this depends on the equinox (not
# the observing time/epoch) of the coordinates. See issue #1496 for a
# discussion of this.
eterms_a = CartesianRepresentation(
u.Quantity(fk4_e_terms(fk4noecoord.equinox), u.dimensionless_unscaled,
copy=False), copy=False)
rep0 = rep.copy()
for _ in range(10):
rep = (eterms_a + rep0) / (1. + eterms_a.dot(rep))
# Find new distance (for re-normalization)
d_new = rep.norm()
# Renormalize
rep *= d_orig / d_new
# now re-cast into an appropriate Representation, and precess if need be
if isinstance(fk4noecoord.data, UnitSphericalRepresentation):
rep = rep.represent_as(UnitSphericalRepresentation)
return fk4frame.realize_frame(rep)
def fk4_to_fk4_no_e(fk4coord, fk4noeframe):
# Extract cartesian vector
rep = fk4coord.cartesian
# Find distance (for re-normalization)
d_orig = rep.norm()
rep /= d_orig
# Apply E-terms of aberration. Note that this depends on the equinox (not
# the observing time/epoch) of the coordinates. See issue #1496 for a
# discussion of this.
eterms_a = CartesianRepresentation(u.Quantity(fk4_e_terms(
fk4coord.equinox),
u.dimensionless_unscaled,
copy=False),
copy=False)
rep = rep - eterms_a + eterms_a.dot(rep) * rep
# Find new distance (for re-normalization)
d_new = rep.norm()
# Renormalize
rep *= d_orig / d_new
# now re-cast into an appropriate Representation, and precess if need be
if isinstance(fk4coord.data, UnitSphericalRepresentation):
rep = rep.represent_as(UnitSphericalRepresentation)
# if no obstime was given in the new frame, use the old one for consistency
newobstime = fk4coord._obstime if fk4noeframe._obstime is None else fk4noeframe._obstime
fk4noe = FK4NoETerms(rep, equinox=fk4coord.equinox, obstime=newobstime)
if fk4coord.equinox != fk4noeframe.equinox:
# precession
fk4noe = fk4noe.transform_to(fk4noeframe)
return fk4noe
