Exemple #1
0
def hipecleq():
    """Print summary of ECL-EQ comparison with SLALIB ecleq (HIP)."""
    hip_tab = get_hipdata()
    sla_tab = get_sla("slalib_hip_ecleq.txt")

    dummy = np.zeros((len(hip_tab['px']), ))
    v6l = convert.cat2v6(hip_tab['elon2'], hip_tab['elat2'], dummy, dummy,
                         dummy, dummy, tpm.CJ)

    v6o = convert.convertv6(v6l, s1=3, s2=6)
    cat = convert.v62cat(v6o, tpm.CJ)

    cat = cat2array(cat)

    ra_diff = np.degrees(cat['alpha']) - sla_tab[:, 0]
    ra_diff = np.abs(ra_diff * 3600.0)
    dec_diff = np.degrees(cat['delta']) - sla_tab[:, 1]
    dec_diff = np.abs(dec_diff * 3600.0)

    print("Comparison with SLALIB ecleq using HIPPARCOS data.")
    fs = "{0} {1}\n" + \
        "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
    x = stats.describe(ra_diff)
    print(fs.format("ra_diff", "arcsec", x[1][0], x[1][1], x[2], x[3]**0.5))
    x = stats.describe(dec_diff)
    print(fs.format("dec_diff", "arcsec", x[1][0], x[1][1], x[2], x[3]**0.5))
Exemple #2
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def hipeqgal():
    """Print summary of EQ-GAL comparison with SLALIB eqgal (HIP)."""
    hip_tab = get_hipdata()
    sla_tab = get_sla("slalib_hip_eqgal.txt")

    dummy = np.zeros((len(hip_tab['px']), ))
    v6l = convert.cat2v6(hip_tab['raj2'], hip_tab['decj2'], dummy, dummy,
                         dummy, dummy, tpm.CJ)

    v6o = convert.convertv6(v6l, s1=6, s2=4)
    # The galactic coordinates are at epoch J2000. But SLALIB
    # results are for B1950. So apply proper motion here.
    v6o = convert.proper_motion(v6o, tpm.B1950, tpm.J2000)
    cat = convert.v62cat(v6o, tpm.CJ)

    cat = cat2array(cat)

    ra_diff = np.degrees(cat['alpha']) - sla_tab[:, 0]
    ra_diff = np.abs(ra_diff * 3600.0)
    dec_diff = np.degrees(cat['delta']) - sla_tab[:, 1]
    dec_diff = np.abs(dec_diff * 3600.0)

    print("Comparison with SLALIB eqgal using HIPPARCOS data.")
    fs = "{0} {1}\n" + \
        "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
    x = stats.describe(ra_diff)
    print(fs.format("ra_diff", "arcsec", x[1][0], x[1][1], x[2], x[3]**0.5))
    x = stats.describe(dec_diff)
    print(fs.format("dec_diff", "arcsec", x[1][0], x[1][1], x[2], x[3]**0.5))
def hipecleq():
    """Print summary of ECL-EQ comparison with SLALIB ecleq (HIP)."""
    hip_tab = get_hipdata()
    sla_tab = get_sla("slalib_hip_ecleq.txt")

    dummy = np.zeros((len(hip_tab['px']),))
    v6l = convert.cat2v6(hip_tab['elon2'], hip_tab['elat2'], dummy, dummy,
                         dummy, dummy, tpm.CJ)

    v6o = convert.convertv6(v6l, s1=3, s2=6)
    cat = convert.v62cat(v6o, tpm.CJ)

    cat = cat2array(cat)

    ra_diff = np.degrees(cat['alpha']) - sla_tab[:, 0]
    ra_diff = np.abs(ra_diff * 3600.0)
    dec_diff = np.degrees(cat['delta']) - sla_tab[:, 1]
    dec_diff = np.abs(dec_diff * 3600.0)

    print("Comparison with SLALIB ecleq using HIPPARCOS data.")
    fs = "{0} {1}\n" + \
        "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
    x = stats.describe(ra_diff)
    print(fs.format("ra_diff", "arcsec", x[1][0], x[1][1], x[2],
                    x[3] ** 0.5))
    x = stats.describe(dec_diff)
    print(fs.format("dec_diff", "arcsec", x[1][0], x[1][1], x[2],
                    x[3] ** 0.5))
def hipgaleq():
    """Print summary of GAL-EQ comparison with SLALIB galeq (HIP)."""
    hip_tab = get_hipdata()
    sla_tab = get_sla("slalib_hip_galeq.txt")

    dummy = np.zeros((len(hip_tab['px']),))
    v6l = convert.cat2v6(hip_tab['glon'], hip_tab['glat'], dummy, dummy,
                         dummy, dummy, tpm.CJ)

    # The actual epoch of galactic data is J2000. But in SLALIB
    # the input is taken to be B1950.0. So use tpm.B1950 as epoch
    # in the conversion.
    v6o = convert.convertv6(v6l, s1=4, s2=6, epoch=tpm.B1950)
    cat = convert.v62cat(v6o, tpm.CJ)

    cat = cat2array(cat)

    ra_diff = np.degrees(cat['alpha']) - sla_tab[:, 0]
    ra_diff = np.abs(ra_diff * 3600.0)
    dec_diff = np.degrees(cat['delta']) - sla_tab[:, 1]
    dec_diff = np.abs(dec_diff * 3600.0)

    print("Comparison with SLALIB galeq using HIPPARCOS data.")
    fs = "{0} {1}\n" + \
        "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
    x = stats.describe(ra_diff)
    print(fs.format("ra_diff", "arcsec", x[1][0], x[1][1], x[2],
                    x[3] ** 0.5))
    x = stats.describe(dec_diff)
    print(fs.format("dec_diff", "arcsec", x[1][0], x[1][1], x[2],
                    x[3] ** 0.5))
def hipeqgal():
    """Print summary of EQ-GAL comparison with SLALIB eqgal (HIP)."""
    hip_tab = get_hipdata()
    sla_tab = get_sla("slalib_hip_eqgal.txt")

    dummy = np.zeros((len(hip_tab['px']),))
    v6l = convert.cat2v6(hip_tab['raj2'], hip_tab['decj2'], dummy, dummy,
                         dummy, dummy, tpm.CJ)

    v6o = convert.convertv6(v6l, s1=6, s2=4)
    # The galactic coordinates are at epoch J2000. But SLALIB
    # results are for B1950. So apply proper motion here.
    v6o = convert.proper_motion(v6o, tpm.B1950, tpm.J2000)
    cat = convert.v62cat(v6o, tpm.CJ)

    cat = cat2array(cat)

    ra_diff = np.degrees(cat['alpha']) - sla_tab[:, 0]
    ra_diff = np.abs(ra_diff * 3600.0)
    dec_diff = np.degrees(cat['delta']) - sla_tab[:, 1]
    dec_diff = np.abs(dec_diff * 3600.0)

    print("Comparison with SLALIB eqgal using HIPPARCOS data.")
    fs = "{0} {1}\n" + \
        "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
    x = stats.describe(ra_diff)
    print(fs.format("ra_diff", "arcsec", x[1][0], x[1][1], x[2],
                    x[3] ** 0.5))
    x = stats.describe(dec_diff)
    print(fs.format("dec_diff", "arcsec", x[1][0], x[1][1], x[2],
                    x[3] ** 0.5))
Exemple #6
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def hipgaleq():
    """Print summary of GAL-EQ comparison with SLALIB galeq (HIP)."""
    hip_tab = get_hipdata()
    sla_tab = get_sla("slalib_hip_galeq.txt")

    dummy = np.zeros((len(hip_tab['px']), ))
    v6l = convert.cat2v6(hip_tab['glon'], hip_tab['glat'], dummy, dummy, dummy,
                         dummy, tpm.CJ)

    # The actual epoch of galactic data is J2000. But in SLALIB
    # the input is taken to be B1950.0. So use tpm.B1950 as epoch
    # in the conversion.
    v6o = convert.convertv6(v6l, s1=4, s2=6, epoch=tpm.B1950)
    cat = convert.v62cat(v6o, tpm.CJ)

    cat = cat2array(cat)

    ra_diff = np.degrees(cat['alpha']) - sla_tab[:, 0]
    ra_diff = np.abs(ra_diff * 3600.0)
    dec_diff = np.degrees(cat['delta']) - sla_tab[:, 1]
    dec_diff = np.abs(dec_diff * 3600.0)

    print("Comparison with SLALIB galeq using HIPPARCOS data.")
    fs = "{0} {1}\n" + \
        "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
    x = stats.describe(ra_diff)
    print(fs.format("ra_diff", "arcsec", x[1][0], x[1][1], x[2], x[3]**0.5))
    x = stats.describe(dec_diff)
    print(fs.format("dec_diff", "arcsec", x[1][0], x[1][1], x[2], x[3]**0.5))
Exemple #7
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def fk5ecl():
    # FK5 equinox and epoch J2000.0, to IAU 1980 ecliptic J2000.0
    v6o = convert.convertv6(v6, s1=6, s2=3)
    # Convert V6C vectors into a list of dictionaries, each of which
    # contain the 6-D Fk4 B1950.0 coordinates.
    cat = convert.v62cat(v6o, tpm.CJ)

    return cat
Exemple #8
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def hipfk425():
    """Print summary of FK4-FK5 comparison with SLALIB fk425 (HIP).

    The input FK4 data is the same generated for the the FK5-FK4
    conversion test. I read that data into slalib and perform the
    reverse conversion. The result is then compared with that from
    PyTPM.
    """
    sla_tabb = get_sla("slalib_hip_fk524.txt")
    sla_tab = get_sla("slalib_hip_fk524_fk425.txt")

    r = np.radians(sla_tabb[:, 0])
    d = np.radians(sla_tabb[:, 1])
    px = sla_tabb[:, 2] / 1000.0
    pma = sla_tabb[:, 3] / 1000.0 * 100.0
    pmd = sla_tabb[:, 4] / 1000.0 * 100.0
    rv = sla_tabb[:, 5]

    v6l = convert.cat2v6(r, d, pma, pmd, px, rv, tpm.CB)
    v6o = convert.convertv6(v6l, s1=5, s2=6, epoch=tpm.B1950)
    v6o = convert.proper_motion(v6o, tpm.J2000, tpm.B1950)
    cat = convert.v62cat(v6o, tpm.CJ)
    cat = cat2array(cat)

    r = np.degrees(cat['alpha'])
    d = np.degrees(cat['delta'])
    # arc-sec/cent. to milli-arcsec/Jul. year.
    pma = cat['pma'] * 1000.0 / 100.0
    pmd = cat['pmd'] * 1000.0 / 100.0
    # arc-sec to milli-arcsec
    px = cat['px'] * 1000.0

    ra_diff = np.abs(r - sla_tab[:, 0]) * 3600.0
    dec_diff = np.abs(d - sla_tab[:, 1]) * 3600.0
    px_diff = np.abs(px - sla_tab[:, 2])
    pma_diff = np.abs(pma - sla_tab[:, 3])
    pmd_diff = np.abs(pmd - sla_tab[:, 4])
    rv_diff = np.abs(rv - sla_tab[:, 5])

    fs = "{0} {1}\n" + \
        "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
    x = [
        stats.describe(np.abs(i))
        for i in [ra_diff, dec_diff, px_diff, pma_diff, pmd_diff, rv_diff]
    ]
    print("Comparison with SLALIB fk425 using HIPPARCOS data.")
    for name, unit, s in zip(
        ["ra_diff", "dec_diff", "px_diff", "pma_diff", "pmd_diff", "rv_diff"],
        [
            "arsec", "arcsec", "milliarcsec", "milli-arsec/trop. yr",
            "milli-arcsec/trop. yr", "km/s"
        ], x):
        print(fs.format(name, unit, s[1][0], s[1][1], s[2], s[3]**0.5))
def hipfk425():
    """Print summary of FK4-FK5 comparison with SLALIB fk425 (HIP).

    The input FK4 data is the same generated for the the FK5-FK4
    conversion test. I read that data into slalib and perform the
    reverse conversion. The result is then compared with that from
    PyTPM.
    """
    sla_tabb = get_sla("slalib_hip_fk524.txt")
    sla_tab = get_sla("slalib_hip_fk524_fk425.txt")

    r = np.radians(sla_tabb[:, 0])
    d = np.radians(sla_tabb[:, 1])
    px = sla_tabb[:, 2] / 1000.0
    pma = sla_tabb[:, 3] / 1000.0 * 100.0
    pmd = sla_tabb[:, 4] / 1000.0 * 100.0
    rv = sla_tabb[:, 5]

    v6l = convert.cat2v6(r, d, pma, pmd, px, rv, tpm.CB)
    v6o = convert.convertv6(v6l, s1=5, s2=6, epoch=tpm.B1950)
    v6o = convert.proper_motion(v6o, tpm.J2000, tpm.B1950)
    cat = convert.v62cat(v6o, tpm.CJ)
    cat = cat2array(cat)

    r = np.degrees(cat['alpha'])
    d = np.degrees(cat['delta'])
    # arc-sec/cent. to milli-arcsec/Jul. year.
    pma = cat['pma'] * 1000.0 / 100.0
    pmd = cat['pmd'] * 1000.0 / 100.0
    # arc-sec to milli-arcsec
    px = cat['px'] * 1000.0

    ra_diff = np.abs(r - sla_tab[:, 0]) * 3600.0
    dec_diff = np.abs(d - sla_tab[:, 1]) * 3600.0
    px_diff = np.abs(px - sla_tab[:, 2])
    pma_diff = np.abs(pma - sla_tab[:, 3])
    pmd_diff = np.abs(pmd - sla_tab[:, 4])
    rv_diff = np.abs(rv - sla_tab[:, 5])

    fs = "{0} {1}\n" + \
        "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
    x = [stats.describe(np.abs(i)) for i in
         [ra_diff, dec_diff, px_diff, pma_diff, pmd_diff, rv_diff]]
    print("Comparison with SLALIB fk425 using HIPPARCOS data.")
    for name, unit, s in zip(
        ["ra_diff", "dec_diff", "px_diff", "pma_diff", "pmd_diff",
         "rv_diff"],
        ["arsec", "arcsec", "milliarcsec", "milli-arsec/trop. yr",
         "milli-arcsec/trop. yr", "km/s"],
        x):
        print(fs.format(name, unit, s[1][0], s[1][1], s[2], s[3] ** 0.5))
Exemple #10
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def fk54():
    # Convert from FK5 equinox and epoch J2000.0 to FK4 equinox B1950, but
    # at the given epoch i.e., J2000.0.
    v6o = convert.convertv6(v6, s1=6, s2=5, epoch=tpm.J2000)

    # Apply proper motion from J2000.0 to B1950.0. Objects with zero
    # velocity in FK5 will have a fictitious proper motion in FK4.
    v6o = convert.proper_motion(v6o, tpm.B1950, tpm.J2000)

    # Convert V6C vectors into a list of dictionaries, each of which
    # contain the 6-D Fk4 B1950.0 coordinates.
    cat = convert.v62cat(v6o, tpm.CB)

    return cat
Exemple #11
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    def fB1950toJ2000_main(ra_J2000, dec_J2000):
        '''
		Precess Right Ascension and Declination coordinates from the sexagismal positions in the B1959 system to decimal degrees in the J2000 system.
		
		Input
		ra_J2000: single Right Ascension position in sexagismal J2000
		dec_J2000: single Declination position in sexagismal J2000
		
		Output
		ra_deg: single Right Ascension position in decimal degree
		dec_deg: single Declination position in decimal degrees
		'''

        # convert decimal degrees to sexagismal format
        ra_sexa, dec_sexa = degtosexa(ra_J2000, dec_J2000)
        # extract RA hh:mm:ss and Dec dd:mm:ss components
        ra_hh = float(ra_sexa.split(" ")[0])
        ra_mm = float(ra_sexa.split(" ")[1])
        ra_ss = float(ra_sexa.split(" ")[2])
        dec_dd = float(dec_sexa.split(" ")[0][1:])
        dec_mm = float(dec_sexa.split(" ")[1])
        dec_ss = float(dec_sexa.split(" ")[2])
        # create RA and Dec objects
        ra_J2000 = tpm.HMS(hh=ra_hh, mm=ra_mm, ss=ra_ss).to_radians()
        dec_J2000 = tpm.DMS(dd=dec_dd, mm=dec_mm, ss=dec_ss).to_radians()
        # velocity vector
        v5 = convert.cat2v6(ra_J2000, dec_J2000)
        v5_fk6 = convert.convertv6(v5,
                                   s1=5,
                                   s2=6,
                                   epoch=tpm.B1950,
                                   equinox=tpm.B1950)
        v5_fk6_ep2000 = convert.proper_motion(v5_fk6, tpm.J2000, tpm.B1950)
        d = convert.v62cat(v5_fk6_ep2000, C=tpm.CJ)
        ra_new_rad = d["alpha"]
        ra_deg = ra_new_rad * 180. / np.pi
        dec_new_rad = d["delta"]
        dec_deg = dec_new_rad * 180. / np.pi

        return ra_deg, dec_deg
Exemple #12
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# Create V6C array from catalog data.
v6l = convert.cat2v6(hip_tab['raj2'], hip_tab['decj2'], hip_tab['pma'],
                     hip_tab['pmd'], hip_tab['px'], rv, tpm.CJ)

# UTC and TDB for mid-night of 2010/1/1.
utc = tpm.gcal2j(2010, 1, 1) - 0.5  # midnight
tt = tpm.utc2tdb(utc)

# Apply proper motion from J2000 to date.
v6o = convert.proper_motion(v6l, tt, tpm.J2000)

# Convert from mean equinox J2000 to true equinox and epoch of date.
v6o = convert.convertv6(v6o, s1=6, s2=11, utc=utc)

# Convert to Numpy rec-array.
cat = convert.v62cat(v6o, tpm.CJ)
cat = cat2array(cat)

ra_diff = np.degrees(cat['alpha']) - tab[:, 0]
ra_diff = np.abs(ra_diff) * 3600.0
dec_diff = np.degrees(cat['delta']) - tab[:, 1]
dec_diff = np.abs(dec_diff) * 3600.0

print("Comparison with SLALIB map using HIPPARCOS data.")
fs = "{0} {1}\n" + \
    "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
x = stats.describe(ra_diff)
print(fs.format("ra_diff", "arcsec", x[1][0], x[1][1], x[2], x[3]**0.5))
x = stats.describe(dec_diff)
print(fs.format("dec_diff", "arcsec", x[1][0], x[1][1], x[2], x[3]**0.5))
Exemple #13
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alt = 35800.26  #m
ut = 2455822.20000367  #julian date

for i in range(0, 1):
    v6 = convert.cat2v6(alpha=az,
                        delta=el,
                        pma=0.0,
                        pmd=0.0,
                        px=0.0,
                        rv=0,
                        C=tpm.CJ)
    start_clock = time.clock()
    v6c = convert.convertv6(v6=v6,
                            utc=ut,
                            s1=tpm.TPM_S19,
                            s2=tpm.TPM_S07,
                            epoch=tpm.J2000,
                            equinox=tpm.J2000,
                            lon=lon,
                            lat=lat,
                            alt=alt,
                            xpole=0.0,
                            ypole=0.0,
                            T=273.15,
                            P=1013.25,
                            H=0.0,
                            wavelength=19986.16386)
    print("TIME[%d]:%.2g s" % (i, time.clock() - start_clock))
    cat = convert.v62cat(v6c)
    print(np.degrees([cat['alpha'], cat['delta']]))
import datetime
import time
import numpy as np

from pytpm import convert, tpm 

az = 3.30084818 #rad
el = 0.94610742 #rad
lat = 34.64 #deg
lon = -103.7 #deg
alt = 35800.26 #m
ut = 2455822.20000367 #julian date

for i in range(0, 1):
    v6 = convert.cat2v6(alpha = az, delta = el, pma=0.0, pmd=0.0, px=0.0, rv=0, C=tpm.CJ)
    start_clock = time.clock()
    v6c = convert.convertv6(v6=v6,
        utc=ut,
        s1=tpm.TPM_S19, s2=tpm.TPM_S07,
        epoch=tpm.J2000, equinox=tpm.J2000,
        lon=lon, lat=lat, alt=alt,
        xpole=0.0, ypole=0.0,
        T=273.15, P=1013.25, H=0.0, wavelength=19986.16386)
    print("TIME[%d]:%.2g s" % (i, time.clock() - start_clock))
    cat = convert.v62cat(v6c)
    print(np.degrees([cat['alpha'], cat['delta']]))
Exemple #15
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# Create V6C array from catalog data.
v6l = convert.cat2v6(hip_tab['raj2'], hip_tab['decj2'], hip_tab['pma'],
                     hip_tab['pmd'], hip_tab['px'], rv, tpm.CJ)

# UTC and TDB for mid-night of 2010/1/1.
utc = tpm.gcal2j(2010, 1, 1) - 0.5  # midnight
tt = tpm.utc2tdb(utc)

# Apply proper motion from J2000 to date.
v6o = convert.proper_motion(v6l, tt, tpm.J2000)

# Convert from mean equinox J2000 to true equinox and epoch of date.
v6o = convert.convertv6(v6o, s1=6, s2=11, utc=utc)

# Convert to Numpy rec-array.
cat = convert.v62cat(v6o, tpm.CJ)
cat = cat2array(cat)

ra_diff = np.degrees(cat['alpha']) - tab[:, 0]
ra_diff = np.abs(ra_diff) * 3600.0
dec_diff = np.degrees(cat['delta']) - tab[:, 1]
dec_diff = np.abs(dec_diff) * 3600.0

print("Comparison with SLALIB map using HIPPARCOS data.")
fs = "{0} {1}\n" + \
    "Min:  {2:.4f} Max: {3:.4f} \nMean: {4:.4f} Std: {5:.4f}\n"
x = stats.describe(ra_diff)
print(fs.format("ra_diff", "arcsec", x[1][0], x[1][1], x[2], x[3] ** 0.5))
x = stats.describe(dec_diff)
print(fs.format("dec_diff", "arcsec", x[1][0], x[1][1], x[2], x[3] ** 0.5))
Exemple #16
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# Dummy radial velocity.
rv = np.zeros_like(hip_tab['px'])

# Create array of TPM V6C vectors.
v6l = convert.cat2v6(hip_tab['raj2'], hip_tab['decj2'], hip_tab['pma'],
                     hip_tab['pmd'], hip_tab['px'], rv, tpm.CJ)

# Time for the observations.
utc = tpm.gcal2j(2010, 1, 1) - 0.5  # midnight
tt = tpm.utc2tdb(utc)

# Convert J2000 RA, DEC to Az, EL and ZD at given UTC.
v6o = convert.proper_motion(v6l, tt, tpm.J2000)
v619 = convert.convertv6(v6o, s1=6, s2=19, utc=utc)
cat19 = convert.v62cat(v619, tpm.CJ)
cat19 = cat2array(cat19)

az = np.degrees(cat19['alpha'])
el = np.degrees(cat19['delta'])
zd = 90.0 - el
# Keep only those objects with ZD < 75.0 degrees.
indx = np.where(zd < 75.0)

# Difference in AZ and ZD, using TPM and SLALIB.
az_diff = np.abs(az[indx] - az_sla[indx]) * 3600.0
zd_diff = np.abs(zd[indx] - zd_sla[indx]) * 3600.0

# Az, El to HA and Dec.
v620 = convert.convertv6(v619, s1=19, s2=20, utc=utc)
cat20 = convert.v62cat(v620, tpm.CJ)
Exemple #17
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# Dummy radial velocity.
rv = np.zeros_like(hip_tab['px'])

# Create array of TPM V6C vectors.
v6l = convert.cat2v6(hip_tab['raj2'], hip_tab['decj2'], hip_tab['pma'],
                     hip_tab['pmd'], hip_tab['px'], rv, tpm.CJ)

# Time for the observations.
utc = tpm.gcal2j(2010, 1, 1) - 0.5  # midnight
tt = tpm.utc2tdb(utc)

# Convert J2000 RA, DEC to Az, EL and ZD at given UTC.
v6o = convert.proper_motion(v6l, tt, tpm.J2000)
v619 = convert.convertv6(v6o, s1=6, s2=19, utc=utc)
cat19 = convert.v62cat(v619, tpm.CJ)
cat19 = cat2array(cat19)

az = np.degrees(cat19['alpha'])
el = np.degrees(cat19['delta'])
zd = 90.0 - el
# Keep only those objects with ZD < 75.0 degrees.
indx = np.where(zd < 75.0)

# Difference in AZ and ZD, using TPM and SLALIB.
az_diff = np.abs(az[indx] - az_sla[indx]) * 3600.0
zd_diff = np.abs(zd[indx] - zd_sla[indx]) * 3600.0

# Az, El to HA and Dec.
v620 = convert.convertv6(v619, s1=19, s2=20, utc=utc)
cat20 = convert.v62cat(v620, tpm.CJ)