def ccFromSCPVOff(pos, pm, parlax, radVel, offDir, offMag):
"""
Converts spherical to cartesian coordinates, including position, velocity
and and a local offset along a great circle from the position vector.
See also ccFromSCPV and ccFromSC.
Inputs:
- pos(2) spherical position (degrees);
pos[1] must be in the range [-90,90]
- pm(2) proper motion (arcsec per century)
- parlax parallax (arcsec)
- radVel radial velocity (km/s, positive receding)
- offDir offset direction (degrees):
dir. of increasing pos[0] = 0, pos[1] = 90
- offMag offset magnitude (degrees on the sky)
Returns:
- p(3) position vector (au)
- v(3) velocity (au per year)
- offP(3) offset position vector (au)
- atInf true if object is very far away (see Details)
Error Conditions:
- Raises ValueError if pos[1] is not in the range -90 to 90 deg
Warnings:
- Negative parallax is silently treated as zero parallax (object at infinity).
Details:
- See Sph.CCFromSCPV for more information.
History
2002-08-22 ROwen Converted to Python from the TCC's sph_SCPVOff2CC 6-1.
"""
# convert spherical position and velocity to cartesian
p, v, atInf = ccFromSCPV(pos, pm, parlax, radVel)
# compute spherical coordinates of the offset position;
# ignore the case of the offset position being at the pole,
# as the standard calculations work fine for that case
# (sets side_bb = 0 and ang_A = ang_C = 90)
ang_A, side_bb, ang_C, offPosAtPole = angSideAng(90.0 - pos[1],
90.0 - offDir, offMag)
offPos = (
pos[0] + ang_C,
90.0 - side_bb,
)
# convert the offset position to cartesian coordinates
# (the offset is assumed to be long a great circle,
# so the magnitude is exactly the same as the un-offset position)
magP = RO.MathUtil.vecMag(p)
offP = ccFromSC(offPos, magP)
return (p, v, offP, atInf)
def ccFromSCPVOff(pos, pm, parlax, radVel, offDir, offMag):
"""
Converts spherical to cartesian coordinates, including position, velocity
and and a local offset along a great circle from the position vector.
See also ccFromSCPV and ccFromSC.
Inputs:
- pos(2) spherical position (degrees);
pos[1] must be in the range [-90,90]
- pm(2) proper motion (arcsec per century)
- parlax parallax (arcsec)
- radVel radial velocity (km/s, positive receding)
- offDir offset direction (degrees):
dir. of increasing pos[0] = 0, pos[1] = 90
- offMag offset magnitude (degrees on the sky)
Returns:
- p(3) position vector (au)
- v(3) velocity (au per year)
- offP(3) offset position vector (au)
- atInf true if object is very far away (see Details)
Error Conditions:
- Raises ValueError if pos[1] is not in the range -90 to 90 deg
Warnings:
- Negative parallax is silently treated as zero parallax (object at infinity).
Details:
- See Sph.CCFromSCPV for more information.
History
2002-08-22 ROwen Converted to Python from the TCC's sph_SCPVOff2CC 6-1.
"""
# convert spherical position and velocity to cartesian
p, v, atInf = ccFromSCPV (pos, pm, parlax, radVel)
# compute spherical coordinates of the offset position;
# ignore the case of the offset position being at the pole,
# as the standard calculations work fine for that case
# (sets side_bb = 0 and ang_A = ang_C = 90)
ang_A, side_bb, ang_C, offPosAtPole = angSideAng (90.0 - pos[1], 90.0 - offDir, offMag)
offPos = (
pos[0] + ang_C,
90.0 - side_bb,
)
# convert the offset position to cartesian coordinates
# (the offset is assumed to be long a great circle,
# so the magnitude is exactly the same as the un-offset position)
magP = RO.MathUtil.vecMag(p)
offP = ccFromSC(offPos, magP)
return (p, v, offP, atInf)
def scFromCCPVOff(p, v, offP):
"""
Converts cartesian position, velocity and offset to spherical coordinates
(see also SCFromCC and SCFromCCPV).
Inputs:
- p(3) position (au)
- v(3) velocity (au per year)
- offP(3) offset position (au)
Returns:
- pos(2) spherical position (degrees)
ranges: axis 1: [0, 360), axis 2: [-90,90]
- pm(2) proper motion (arcsec per century)
- parlax parallax (arcsec)
- radVel radial velocity (km/s)
- offDir offset direction (degrees):
dir. of increasing pos[0] = 0
dir. of increasing pos[1] = 90
- offMag magnitude of offset (degrees on the sky)
- atPole true if at a pole; see "Error Cond." for implications
Error Conditions:
- Raises ValueError if |p| is too small to safely compute.
- If p is very near a pole, atPole is set true,
pos[1], pm[0], pm[1] and offDir are set to zero;
pos[0], parlax, radVel and offMag are still computed correctly
(pos[0] is +/-90.0, as appropriate).
- If inputs are too large, overflows are possible--roughly if p^2 or v^2 overflows.
History
2002-08-22 ROwen Converted to Python from the TCC's sph_CCPVOff2SC 6-1.
"""
# convert p and v from cartesian to spherical
pos, pm, parlax, radVel, atPole = scFromCCPV(p, v)
# convert offP from cartesian to spherical
offPos, magOffP, offAtPole = scFromCC(offP)
# compute offset direction and magnitude
ang_A, side_bb, ang_C, offAtPole2 = angSideAng(
90.0 - pos[1], offPos[0] - pos[0], 90.0 - offPos[1],
)
offMag = side_bb
if atPole:
offDir = 0.0
else:
offDir = 90.0 - ang_C
return (pos, pm, parlax, radVel, offDir, offMag, atPole)