def TEME2ECI_pos(Pos_TEME, t):
T = Time(t, format='jd', scale='utc')
dist_vect = norm(Pos_TEME, axis=0)
ra_vect = np.arctan2(Pos_TEME[1], Pos_TEME[0])
dec_vect = np.arcsin(Pos_TEME[2] / dist_vect)
Pos_TEME_SC = PrecessedGeocentric(ra=ra_vect * u.rad,
dec=dec_vect * u.rad, distance=dist_vect * u.m, equinox=T, obstime=T)
Pos_ECI_SC = Pos_TEME_SC.transform_to(GCRS(obstime=T))
Pos_ECI = np.vstack(Pos_ECI_SC.cartesian.xyz.value)
return Pos_ECI
def test_transforms_diff(sc):
# note that arguably this *should* fail for the no-distance cases: 3D
# information is necessary to truly solve this, hence the xfail
if not sc.distance.unit.is_equivalent(u.m):
pytest.xfail('Should fail for no-distance cases')
else:
trans = sc.transform_to(PrecessedGeocentric(equinox='B1975'))
assert isinstance(trans.frame, PrecessedGeocentric)
def test_precessed_geocentric_different_obstime():
# Create two PrecessedGeocentric frames with different obstime
precessedgeo1 = PrecessedGeocentric(obstime='2021-09-07')
precessedgeo2 = PrecessedGeocentric(obstime='2021-06-07')
# GCRS->PrecessedGeocentric should give different results for the two frames
gcrs_coord = GCRS(10 * u.deg,
20 * u.deg,
3 * u.AU,
obstime=precessedgeo1.obstime)
pg_coord1 = gcrs_coord.transform_to(precessedgeo1)
pg_coord2 = gcrs_coord.transform_to(precessedgeo2)
assert not pg_coord1.is_equivalent_frame(pg_coord2)
assert not allclose(pg_coord1.cartesian.xyz, pg_coord2.cartesian.xyz)
# Looping back to GCRS should return the original coordinate
loopback1 = pg_coord1.transform_to(gcrs_coord)
loopback2 = pg_coord2.transform_to(gcrs_coord)
assert loopback1.is_equivalent_frame(gcrs_coord)
assert loopback2.is_equivalent_frame(gcrs_coord)
assert_allclose(loopback1.cartesian.xyz, gcrs_coord.cartesian.xyz)
assert_allclose(loopback2.cartesian.xyz, gcrs_coord.cartesian.xyz)
def test_precessed_geocentric():
assert PrecessedGeocentric().equinox.jd == Time('J2000').jd
gcrs_coo = GCRS(180 * u.deg, 2 * u.deg, distance=10000 * u.km)
pgeo_coo = gcrs_coo.transform_to(PrecessedGeocentric())
assert np.abs(gcrs_coo.ra - pgeo_coo.ra) > 10 * u.marcsec
assert np.abs(gcrs_coo.dec - pgeo_coo.dec) > 10 * u.marcsec
assert_allclose(gcrs_coo.distance, pgeo_coo.distance)
gcrs_roundtrip = pgeo_coo.transform_to(GCRS())
assert_allclose(gcrs_coo.ra, gcrs_roundtrip.ra)
assert_allclose(gcrs_coo.dec, gcrs_roundtrip.dec)
assert_allclose(gcrs_coo.distance, gcrs_roundtrip.distance)
pgeo_coo2 = gcrs_coo.transform_to(PrecessedGeocentric(equinox='B1850'))
assert np.abs(gcrs_coo.ra - pgeo_coo2.ra) > 1.5 * u.deg
assert np.abs(gcrs_coo.dec - pgeo_coo2.dec) > 0.5 * u.deg
assert_allclose(gcrs_coo.distance, pgeo_coo2.distance)
gcrs2_roundtrip = pgeo_coo2.transform_to(GCRS())
assert_allclose(gcrs_coo.ra, gcrs2_roundtrip.ra)
assert_allclose(gcrs_coo.dec, gcrs2_roundtrip.dec)
assert_allclose(gcrs_coo.distance, gcrs2_roundtrip.distance)
def ECI2TEME_pos(Pos_ECI, t):
T = Time(t, format='jd', scale='utc')
precessed_frame = PrecessedGeocentric(equinox=T, obstime=T)
dist_vect = norm(Pos_ECI, axis=0)
ra_vect = np.arctan2(Pos_ECI[1], Pos_ECI[0])
dec_vect = np.arcsin(Pos_ECI[2] / dist_vect)
Pos_ECI_SC = GCRS(ra=ra_vect * u.rad, dec=dec_vect * u.rad,
distance=dist_vect * u.m, obstime=T)
Pos_TEME_SC = Pos_ECI_SC.transform_to(precessed_frame)
Pos_TEME = np.vstack(Pos_TEME_SC.cartesian.xyz.value)
return Pos_TEME
def test_precessedgeocentric_loopback():
from_coo = PrecessedGeocentric(1 * u.deg,
2 * u.deg,
3 * u.AU,
obstime='2001-01-01',
equinox='2001-01-01')
# Change just the obstime
to_frame = PrecessedGeocentric(obstime='2001-06-30', equinox='2001-01-01')
explicit_coo = from_coo.transform_to(ICRS()).transform_to(to_frame)
implicit_coo = from_coo.transform_to(to_frame)
# Confirm that the explicit transformation changes the coordinate
assert not allclose(explicit_coo.ra, from_coo.ra, rtol=1e-10)
assert not allclose(explicit_coo.dec, from_coo.dec, rtol=1e-10)
assert not allclose(explicit_coo.distance, from_coo.distance, rtol=1e-10)
# Confirm that the loopback matches the explicit transformation
assert_allclose(explicit_coo.ra, implicit_coo.ra, rtol=1e-10)
assert_allclose(explicit_coo.dec, implicit_coo.dec, rtol=1e-10)
assert_allclose(explicit_coo.distance, implicit_coo.distance, rtol=1e-10)
# Change just the equinox
to_frame = PrecessedGeocentric(obstime='2001-01-01', equinox='2001-06-30')
explicit_coo = from_coo.transform_to(ICRS()).transform_to(to_frame)
implicit_coo = from_coo.transform_to(to_frame)
# Confirm that the explicit transformation changes the direction but not the distance
assert not allclose(explicit_coo.ra, from_coo.ra, rtol=1e-10)
assert not allclose(explicit_coo.dec, from_coo.dec, rtol=1e-10)
assert allclose(explicit_coo.distance, from_coo.distance, rtol=1e-10)
# Confirm that the loopback matches the explicit transformation
assert_allclose(explicit_coo.ra, implicit_coo.ra, rtol=1e-10)
assert_allclose(explicit_coo.dec, implicit_coo.dec, rtol=1e-10)
assert_allclose(explicit_coo.distance, implicit_coo.distance, rtol=1e-10)
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 = parse_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 currentgeocentframe(time) : # Generate a PrecessedGeocentric frame for the current equinox. time_ep = 2000. + (time.jd - thorconsts.J2000) / 365.25 eq = "J%7.2f" % (time_ep) # print eq return PrecessedGeocentric(equinox = eq)
# -*- coding: utf-8 -*-
"""
Created on Sat Feb 1 16:59:43 2020
https://qiita.com/phyblas/items/a801b0f319742245ad2e
@author: PC
"""
from astropy.coordinates import SkyCoord, PrecessedGeocentric
b1875 = PrecessedGeocentric(equinox='B1875')
b1875_hokkyoku = SkyCoord(ra=0, dec=90, unit='deg', frame=b1875)
print(b1875_hokkyoku)
b1875_hokkyoku_icrs = b1875_hokkyoku.transform_to('icrs')
print(b1875_hokkyoku_icrs)
def obj_sight(date,objname,lonstr,latstr,tzinhours,approx=True):
"""
date: string, date of observing.
objname : string, name of sun, moon or planet in solar system.
lonstr : string, longitute of observing location on earth.
latstr : string, latitute of observing location on earth.
ltzinhours : float, time zone in hours of observing location.
approx : bool, True for delta_ut1_utc=0
return : print out rise time, set time, transit time and cooresponding alt/az.
"""
lon=Angle(lonstr)
lat=Angle(latstr)
if objname=='sun':
r_obj=const.R_sun.to('m').value
else:
if objname=="moon":
r_obj=1737000
#halfdisk=Angle(diskanglestr)*0.5
date=Time(Time(date,out_subfmt='date').iso)
times=date+np.linspace(0.,1440.,1441)*TimeDelta(60,format='sec') # 每分鐘計算位置
deltat=tzinhours*TimeDelta(3600,format='sec')
a=const.R_earth.to('m').value # 地球半徑
with solar_system_ephemeris.set('jpl'):
n=len(times)
gmttimes=times-deltat # 世界時間 UTC
# 標的物在真赤道座標系統座標
bodies=get_body(objname,gmttimes).transform_to(PrecessedGeocentric(equinox=gmttimes))
if approx:
gmttimes.delta_ut1_utc = 0.
sides=gmttimes.sidereal_time('apparent', 'greenwich')+lon # local sidereal time
x=bodies.cartesian.x.to('m').value # x,y,z為標的物在及時赤道座標系統的直角座標
y=bodies.cartesian.y.to('m').value
z=bodies.cartesian.z.to('m').value
px=np.array(a*np.cos(lat)*np.cos(sides)) # px,py,pz 為觀測地在真赤道座標系統的直角坐標
py=np.array(a*np.cos(lat)*np.sin(sides))
pz=np.array(a*np.sin(lat)*np.ones(n))
positions=np.vstack((px,py,pz)).T # n x 3 array
objs=np.vstack((x,y,z)).T # n x 3 array
# e_z 的每一行為天頂方向單位向量，e_n的每一行為地表往北單位向量，e_e的每一行為地表往東單位向量
e_z=np.vstack((np.cos(lat)*np.cos(sides),np.cos(lat)*np.sin(sides),np.sin(lat)*np.ones(n))) # 3 x n
e_n=np.vstack((-np.sin(lat)*np.cos(sides),-np.sin(lat)*np.sin(sides),np.cos(lat)*np.ones(n))) # 3 x n
e_e=np.vstack((-np.sin(sides),np.cos(sides),np.zeros(n))) # 3 x n
coords=np.zeros((n,3)) # coords 的每一列代表標的物在地表座標系統的直角坐標
az=np.zeros(n) # az 標的物的方位角，北方為0，往東為正，正東方90度，正南方180度，正西方270度。
alt=np.zeros(n) # alt 標的物的仰角
for i in range(n):
coords[i]=np.array(np.vstack((e_e[:,i],e_n[:,i],e_z[:,i]))).dot(objs[i]-positions[i])
r=np.sqrt(coords[i][0]**2+coords[i][1]**2)
rho=np.sqrt(coords[i][0]**2+coords[i][1]**2+coords[i][2]**2)
alt[i]=np.arcsin(coords[i][2]/rho)*180/np.pi
az[i]=np.arctan2(coords[i][0],coords[i][1])*180/np.pi
if az[i]<0:
az[i]=az[i]+360
if objname=="sun" or objname=="moon" :
halfdisk=np.arcsin(r_obj/rho)*180/np.pi*u.deg
else :
halfdisk=0*u.deg
thresh=-(halfdisk+Angle("0d34m0s")).deg # 大氣折射，讓光線轉彎了34角分
altdiff=alt-thresh # altdif 變號的時候就是標的物升起或沉沒的區間，用內插進行估計
for i in range(len(times)-1):
if altdiff[i]*altdiff[i+1] <=0 :
t=times[i]+(times[i+1]-times[i])*(0-altdiff[i])/(altdiff[i+1]-altdiff[i])
if altdiff[i]<0:
print("出",t,"方位",az[i])
else:
print("沒",t,"方位",az[i])
if not (az[i] // 180 == az[i+1] // 180) and alt[i]>0:
if np.abs(az[i]-180)<30:
ratio=(180-az[i])/(az[i+1]-az[i])
t=times[i]+(times[i+1]-times[i])*ratio
print("中天",t,"仰角",alt[i]+(alt[i+1]-alt[i])*ratio,"方位","南")
else:
left=az[i]
right=az[i+1]
if left>300:
left=left-360
if right>300:
right=right-360
ratio=(0-left)/(az[i+1]-az[i])
t=times[i]+(times[i+1]-times[i])*ratio
print("中天",t,"仰角",alt[i]+(alt[i+1]-alt[i])*ratio,"方位","南")
