def test_ensure_unix(self):
# Check that ensure_unix is doing its job for both scalar and array
# inputs
dt = datetime(2016, 4, 3, 2, 1, 0)
dt_list = [
datetime(2016, 4, 3, 2, 1, 0),
datetime(2016, 4, 3, 2, 1, 0)
]
ut = ctime.datetime_to_unix(dt)
ut_array = ctime.datetime_to_unix(dt_list)
sf = ctime.unix_to_skyfield_time(ut)
sf_array = ctime.unix_to_skyfield_time(ut_array)
self.assertEqual(ctime.ensure_unix(dt), ut)
self.assertEqual(ctime.ensure_unix(ut), ut)
self.assertAlmostEqual(ctime.ensure_unix(sf), ut, 3)
self.assertTrue((ctime.ensure_unix(dt_list) == ut_array).all())
self.assertTrue((ctime.ensure_unix(ut_array) == ut_array).all())
self.assertTrue(
np.allclose(ctime.ensure_unix(sf_array),
ut_array,
rtol=1e-10,
atol=1e-4))
def test_time_precision(self):
"""Make sure we have ~0.03 ms precision and that we aren't overflowing
anything at double precision. This number comes from the precision on
Julian date time representations:
http://aa.usno.navy.mil/software/novas/USNOAA-TN2011-02.pdf
"""
delta = 0.001 # Try a 1 ms shift
unix_time = time.time()
unix_time2 = unix_time + delta
tt1 = ctime.unix_to_skyfield_time(unix_time).tt_calendar()
tt2 = ctime.unix_to_skyfield_time(unix_time2).tt_calendar()
err = abs(tt2[-1] - tt1[-1] - delta)
self.assertTrue(err < 4e-5) # Check that it is accurate at the 0.03 ms level.
def test_time_precision(self):
"""Make sure we have ~0.03 ms precision and that we aren't overflowing
anything at double precision. This number comes from the precision on
Julian date time representations:
http://aa.usno.navy.mil/software/novas/USNOAA-TN2011-02.pdf
"""
delta = 0.001 # Try a 1 ms shift
unix_time = time.time()
unix_time2 = unix_time + delta
tt1 = ctime.unix_to_skyfield_time(unix_time).tt_calendar()
tt2 = ctime.unix_to_skyfield_time(unix_time2).tt_calendar()
err = abs(tt2[-1] - tt1[-1] - delta)
self.assertTrue(
err < 4e-5) # Check that it is accurate at the 0.03 ms level.
def test_array(self):
# Do a simple test of transit_RA in an array. Use the fact that the RA
# advances predictably to predict the answers
from skyfield import earthlib
epoch = datetime(2000, 1, 1, 11, 58, 56)
# Create an observer at an arbitrary location
obs = ctime.Observer(118.3, 36.1)
# Calculate LST
t = ctime.unix_to_skyfield_time(ctime.datetime_to_unix(epoch))
gst = earthlib.sidereal_time(t)
lst = (360.0 * gst / 24.0 + obs.longitude) % 360.0
# Drift rate should be very close to 1 degree/4minutes.
# Fetch times calculated by ephem
delta_deg = np.arange(20)
delta_deg.shape = (5, 4)
lst = lst + delta_deg
# Calculate RA using transit_RA
unix_epoch = ctime.datetime_to_unix(epoch)
unix_times = unix_epoch + (delta_deg * 60 * 4 * ctime.SIDEREAL_S)
TRA = obs.transit_RA(unix_times)
# Compare
self.assertTrue(np.allclose(lst, TRA, atol=0.02, rtol=1e-10))
def icrs_to_cirs(ra, dec, epoch, apparent=True):
"""Convert a set of positions from ICRS to CIRS at a given data.
Parameters
----------
ra, dec : float or np.ndarray
Positions of source in ICRS coordinates including an optional
redshift position.
epoch : time_like
Time to convert the positions to. Can be any type convertible to a
time using `caput.time.ensure_unix`.
apparent : bool
Calculate the apparent position (includes abberation and deflection).
Returns
-------
ra_cirs, dec_cirs : float or np.ndarray
Arrays of the positions in *CIRS* coordiantes.
"""
positions = Star(ra=Angle(degrees=ra), dec=Angle(degrees=dec))
epoch = ctime.unix_to_skyfield_time(ctime.ensure_unix(epoch))
earth = ctime.skyfield_wrapper.ephemeris["earth"]
positions = earth.at(epoch).observe(positions)
if apparent:
positions = positions.apparent()
ra_cirs, dec_cirs, _ = positions.cirs_radec(epoch)
return ra_cirs._degrees, dec_cirs._degrees
def test_array(self):
# Do a simple test of transit_RA in an array. Use the fact that the RA
# advances predictably to predict the answers
from skyfield import earthlib
epoch = datetime(2000, 1, 1, 11, 58, 56)
# Create an observer at an arbitrary location
obs = ctime.Observer(118.3, 36.1)
# Calculate LST
t = ctime.unix_to_skyfield_time(ctime.datetime_to_unix(epoch))
gst = earthlib.sidereal_time(t)
lst = (360.0 * gst / 24.0 + obs.longitude) % 360.0
# Drift rate should be very close to 1 degree/4minutes.
# Fetch times calculated by ephem
delta_deg = np.arange(20)
delta_deg.shape = (5, 4)
lst = lst + delta_deg
# Calculate RA using transit_RA
unix_epoch = ctime.datetime_to_unix(epoch)
unix_times = unix_epoch + (delta_deg * 60 * 4 * ctime.SIDEREAL_S)
TRA = obs.transit_RA(unix_times)
# Compare
self.assertTrue(np.allclose(lst, TRA, atol=0.02, rtol=1e-10))
def test_ensure_unix(self):
# Check that ensure_unix is doing its job for both scalar and array
# inputs
dt = datetime(2016, 4, 3, 2, 1, 0)
dt_list = [datetime(2016, 4, 3, 2, 1, 0), datetime(2016, 4, 3, 2, 1, 0)]
ut = ctime.datetime_to_unix(dt)
ut_array = ctime.datetime_to_unix(dt_list)
sf = ctime.unix_to_skyfield_time(ut)
sf_array = ctime.unix_to_skyfield_time(ut_array)
self.assertEqual(ctime.ensure_unix(dt), ut)
self.assertEqual(ctime.ensure_unix(ut), ut)
self.assertAlmostEqual(ctime.ensure_unix(sf), ut, 3)
self.assertTrue((ctime.ensure_unix(dt_list) == ut_array).all())
self.assertTrue((ctime.ensure_unix(ut_array) == ut_array).all())
self.assertTrue(np.allclose(ctime.ensure_unix(sf_array), ut_array, rtol=1e-10, atol=1e-4))
def object_coords(body, date=None, deg=False, obs=chime):
"""Calculates the RA and DEC of the source.
Gives the ICRS coordinates if no date is given (=J2000), or if a date is
specified gives the CIRS coordinates at that epoch.
This also returns the *apparent* position, including abberation and
deflection by gravitational lensing. This shifts the positions by up to
20 arcseconds.
Parameters
----------
body : skyfield source
skyfield.starlib.Star or skyfield.vectorlib.VectorSum or
skyfield.jpllib.ChebyshevPosition body representing the source.
date : float
Unix time at which to determine ra of source If None, use Jan 01
2000.
deg : bool
Return RA ascension in degrees if True, radians if false (default).
obs : `caput.time.Observer`
An observer instance to use. If not supplied use `chime`. For many
calculations changing from this default will make little difference.
Returns
-------
ra, dec: float
Position of the source.
"""
if date is None: # No date, get ICRS coords
if isinstance(body, skyfield.starlib.Star):
ra, dec = body.ra.radians, body.dec.radians
else:
raise ValueError(
"Body is not fixed, cannot calculate coordinates without a date."
)
else: # Calculate CIRS position with all corrections
date = unix_to_skyfield_time(date)
radec = obs.skyfield_obs().at(date).observe(
body).apparent().cirs_radec(date)
ra, dec = radec[0].radians, radec[1].radians
# If requested, convert to degrees
if deg:
ra = np.degrees(ra)
dec = np.degrees(dec)
# Return
return ra, dec
def _gen_basis(self, times, vis, n, max_za=90.):
# make za axis
max_sinza = np.sin(np.radians(max_za))
if self.harm_basis:
sinza = np.linspace(-max_sinza, max_sinza,
2 * int(2 * np.radians(max_za) / np.pi * n))
else:
sinza = np.linspace(-max_sinza, max_sinza, n)
za = np.arcsin(sinza)
az = np.zeros_like(za)
az[:az.shape[0] / 2] = 180.
alt = 90. - np.cos(np.radians(az)) * np.degrees(za)
self.za = za
self.sinza = sinza
self._basis = np.zeros((vis.shape[0], vis.shape[1], n),
dtype=np.complex64)
# make EW grid to integrate over
phi = np.linspace(-2 * self._res(), 2 * self._res(), 20)
z, p = np.meshgrid(za, phi)
self.z, self.p = z, p
alt, az = tel2azalt(z, p)
# model the EW beam as a sinc
ew_beam = cylbeam.fraunhofer_cylinder(lambda x: np.ones_like(x), 20.)
ew_beam = ew_beam(p)**2
self.ew_beam = ew_beam
# calculate phases within beam
phases = np.exp(1j * self._fringe_phase(z, p))
for i, t in enumerate(times):
sf_t = unix_to_skyfield_time(t)
pix = np.zeros((alt.shape[0], alt.shape[1]), dtype=int)
for j in range(alt.shape[0]):
for k in range(alt.shape[1]):
pos = self.obs.at(sf_t).from_altaz(
az_degrees=np.degrees(az[j, k]),
alt_degrees=np.degrees(alt[j, k]))
gallat, gallon = pos.galactic_latlon()[:2]
pix[j, k] = healpy.ang2pix(self.nside,
gallon.degrees,
gallat.degrees,
lonlat=True)
if len(phases.shape) > 2:
basis = np.sum(self.smoothmap[pix] * ew_beam * phases, axis=1)
else:
basis = self.smoothmap[pix] * ew_beam * phases
if self.harm_basis:
# convolve NS slice with basis functions
basis = np.dot(
basis,
np.sin(
np.arange(1, n + 1)[np.newaxis, :] *
(za[:, np.newaxis] + np.pi / 2)))
self._basis[:, i, :] = basis
def test_from_unix_time(self):
"""Make sure we are properly parsing the unix time.
This is as much a test of ephem as our code. See issue #29 on the
PyEphem github page.
"""
unix_time = random.random() * 2e6
dt = datetime.utcfromtimestamp(unix_time)
st = ctime.unix_to_skyfield_time(unix_time)
new_dt = st.utc_datetime()
self.assertEqual(dt.year, new_dt.year)
self.assertEqual(dt.month, new_dt.month)
self.assertEqual(dt.day, new_dt.day)
self.assertEqual(dt.hour, new_dt.hour)
self.assertEqual(dt.minute, new_dt.minute)
self.assertEqual(dt.second, new_dt.second)
self.assertTrue(abs(dt.microsecond - new_dt.microsecond) <= 1000) # Skyfield rounds its output at the millisecond level.
def utc_lst_to_mjd(datestring, lst, obs=chime):
"""Convert datetime string and LST to corresponding modified Julian Day
Parameters
----------
datestring : string
Date as YYYYMMDD-AAA, where AAA is one of [UTC, PST, PDT]
lst : float
Local sidereal time at DRAO (CHIME) in decimal hours
obs : caput.Observer object
Returns
-------
mjd : float
Modified Julian Date corresponding to the given time.
"""
return (unix_to_skyfield_time(
obs.lsa_to_unix(lst * 360 / 24, datetime_to_unix(
parse_date(datestring)))).tt - 2400000.5)
def test_from_unix_time(self):
"""Make sure we are properly parsing the unix time.
This is as much a test of ephem as our code. See issue #29 on the
PyEphem github page.
"""
unix_time = random.random() * 2e6
dt = datetime.utcfromtimestamp(unix_time)
st = ctime.unix_to_skyfield_time(unix_time)
new_dt = st.utc_datetime()
self.assertEqual(dt.year, new_dt.year)
self.assertEqual(dt.month, new_dt.month)
self.assertEqual(dt.day, new_dt.day)
self.assertEqual(dt.hour, new_dt.hour)
self.assertEqual(dt.minute, new_dt.minute)
self.assertEqual(dt.second, new_dt.second)
self.assertTrue(
abs(dt.microsecond - new_dt.microsecond) <=
1000) # Skyfield rounds its output at the millisecond level.
def test_epoch(self):
from skyfield import earthlib
# At the J2000 epoch, sidereal time and transit RA should be the same.
epoch = datetime(2000, 1, 1, 11, 58, 56)
# Create an observer at an arbitrary location
obs = ctime.Observer(118.3, 36.1)
# Calculate the transit_RA
unix_epoch = ctime.datetime_to_unix(epoch)
TRA = obs.transit_RA(unix_epoch)
# Calculate LST
t = ctime.unix_to_skyfield_time(unix_epoch)
gst = earthlib.sidereal_time(t)
lst = (360.0 * gst / 24.0 + obs.longitude) % 360.0
# Tolerance limited by stellar aberation
self.assertTrue(np.allclose(lst, TRA, atol=0.01, rtol=1e-10))
def test_epoch(self):
from skyfield import earthlib
# At the J2000 epoch, sidereal time and transit RA should be the same.
epoch = datetime(2000, 1, 1, 11, 58, 56)
# Create an observer at an arbitrary location
obs = ctime.Observer(118.3, 36.1)
# Calculate the transit_RA
unix_epoch = ctime.datetime_to_unix(epoch)
TRA = obs.transit_RA(unix_epoch)
# Calculate LST
t = ctime.unix_to_skyfield_time(unix_epoch)
gst = earthlib.sidereal_time(t)
lst = (360.0 * gst / 24.0 + obs.longitude) % 360.0
# Tolerance limited by stellar aberation
self.assertTrue(np.allclose(lst, TRA, atol=0.01, rtol=1e-10))
