def topoFromGeoSimple(appGeoP, last, lat):
"""Converts apparent topocentric position to apparent geocentric.
"Simple" because it only corrects for local sidereal time,
ignoring diurnal parallax, diurnal aberration and pole wander.
Inputs:
- appGeoP(3) apparent geocentric cartesian position (RA/Dec)
- last local apparent sidereal time (deg)
- lat latitude (deg)
Returns:
- appTopoP(3) apparent topocentric cartesian position (az, alt), a numpy.array
Note: unlike topoFromGeo, the position units need not be au;
the output position will be the same units as the input position.
Sign convention:
increasing azAlt[x] is south-ish
increasing azAlt[y] is east
"""
sinLAST = RO.MathUtil.sind (last)
cosLAST = RO.MathUtil.cosd (last)
# rotate position and offset to (-HA)/Dec (still cartesian, of course)
posA = (
cosLAST * appGeoP(1) + sinLAST * appGeoP(2),
- sinLAST * appGeoP(1) + cosLAST * appGeoP(2).
appGeoP(3),
)
return azAltFromHADec (posA, lat)
def topoFromGeo(appGeoP, last, obsData):
"""
Converts apparent geocentric coordinates to apparent topocentric coordinates
(not corrected for refraction).
Inputs:
- appGeoP(3) current app. geocentric cartesian position (au) (RA/Dec)
- last local apparent sidereal time, as an angle (deg)
- obsData an ObserverData object
Returns:
- appTopo(3) apparent topocentric cartesian position (au) (az/alt), a numpy.array
Details:
The following approximation is used:
- pole wander is ignored
References:
P.T. Wallace, "Proposals for Keck Tel. Pointing Algorithms", 1986 (unpub)
"""
sinLAST = RO.MathUtil.sind (last)
cosLAST = RO.MathUtil.cosd (last)
# rotate position and offset to (-ha)/Dec (still cartesian, of course)
posA = numpy.array((
cosLAST * appGeoP[0] + sinLAST * appGeoP[1],
-sinLAST * appGeoP[0] + cosLAST * appGeoP[1],
appGeoP[2],
))
# correct position for diurnal parallax
posB = posA - obsData.p
# correct position for diurnal aberration
# follows Pat Wallace's AOPQK
bDir, bMag = llv.vn(posB)
diurAbScaleCorr = 1.0 - (obsData.diurAbVecMag * bDir[1])
posC = numpy.array ((
posB[0] * diurAbScaleCorr,
(posB[1] + (obsData.diurAbVecMag * bMag)) * diurAbScaleCorr,
posB[2] * diurAbScaleCorr,
))
# rotate position (posC) to alt/az;
return azAltFromHADec (posC, obsData.latitude)
def topoFromGeo(appGeoP, last, obsData):
"""
Converts apparent geocentric coordinates to apparent topocentric coordinates
(not corrected for refraction).
Inputs:
- appGeoP(3) current app. geocentric cartesian position (au) (RA/Dec)
- last local apparent sidereal time, as an angle (deg)
- obsData an ObserverData object
Returns:
- appTopo(3) apparent topocentric cartesian position (au) (az/alt), a numpy.array
Details:
The following approximation is used:
- pole wander is ignored
References:
P.T. Wallace, "Proposals for Keck Tel. Pointing Algorithms", 1986 (unpub)
"""
sinLAST = RO.MathUtil.sind(last)
cosLAST = RO.MathUtil.cosd(last)
# rotate position and offset to (-ha)/Dec (still cartesian, of course)
posA = numpy.array((
cosLAST * appGeoP[0] + sinLAST * appGeoP[1],
-sinLAST * appGeoP[0] + cosLAST * appGeoP[1],
appGeoP[2],
))
# correct position for diurnal parallax
posB = posA - obsData.p
# correct position for diurnal aberration
# follows Pat Wallace's AOPQK
bDir, bMag = llv.vn(posB)
diurAbScaleCorr = 1.0 - (obsData.diurAbVecMag * bDir[1])
posC = numpy.array((
posB[0] * diurAbScaleCorr,
(posB[1] + (obsData.diurAbVecMag * bMag)) * diurAbScaleCorr,
posB[2] * diurAbScaleCorr,
))
# rotate position (posC) to alt/az;
return azAltFromHADec(posC, obsData.latitude)
