astroconst package


Module contents

AstroConst package

A Python package that provides astronomical constants. The code is being developed by Marc van der Sluys of the department of Astrophysics at the Radboud University Nijmegen, the Institute of Nuclear and High-Energy Physics (Nikhef), and the Institute for Gravitational and Subatomic Physics (GRASP) at Utrecht University, all in The Netherlands. The AstroConst package can be used under the conditions of the EUPL 1.2 licence. These pages contain the API documentation. For more information on the Python package, licence and source code, see the AstroConst GitHub page.

astroconst.a_rad = 7.56572310579377e-16

Radiation (density) constant, 7.56591e-16 J m^-3 K^-4

astroconst.am2r = 0.0002908882086657216

Factor to convert arcminutes to radians

astroconst.amu = 1.66053904e-27

Atomic mass unit; (mass of C12 atom)/12, 1.6605402e-27 kg

astroconst.as2r = 4.84813681109536e-06

Factor to convert arcseconds to radians. = 149597870700

Astronomical unit

astroconst.c = 299792458

Speed of light in vacuo

astroconst.c2k = 273.15

Degrees Celcius to Kelvin (shift) = 0.01

Centimeter in SI (m)

astroconst.d2h = 0.06666666666666667

Factor to convert degrees to hours

astroconst.d2r = 0.017453292519943295

Factor to convert degrees to radians. = 86400.0

Default day == solar day = 86400 s

astroconst.day_sid = 0.997269663

Siderial day in days

astroconst.day_sol = 86400.0

Solar day = 86400 s

astroconst.dec_gp_2000 = 0.4734773

27.12825° in rad


Dec of the Galactic pole for J2000

astroconst.dow_en = array(['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday',        'Saturday'], dtype='<U9')

Capitalised day-of-week names in English.

astroconst.dow_en_abr = array(['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'], dtype='<U3')

Capitalised three-letter day-of-week abbreviations in English.

astroconst.dow_en_abr2 = array(['Su', 'Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa'], dtype='<U2')

Capitalised two-letter day-of-week abbreviations in English.

astroconst.dow_nl = array(['zondag', 'maandag', 'dinsdag', 'woensdag', 'donderdag', 'vrijdag',        'zaterdag'], dtype='<U9')

Lower-case day-of-week names in Dutch.

astroconst.dow_nl_abr = array(['zo', 'ma', 'di', 'wo', 'do', 'vr', 'za'], dtype='<U2')

Lower-case two-letter day-of-week abbreviations in Dutch.

astroconst.dow_nl_abr4 = array(['zon', 'maa', 'din', 'woe', 'don', 'vrij', 'zat'], dtype='<U4')

Lower-case four-letter day-of-week abbreviations in Dutch.

astroconst.dst_en = array(['standard time', 'daylight-savings time'], dtype='<U21')

English DST timezone names.

astroconst.dst_nl = array(['wintertijd', 'zomertijd'], dtype='<U10')

Dutch DST timezone names.

astroconst.eV = 1.6021766208e-19

1.6021766e-19 J


Elementary (electron) charge in Coulomb; ElectronVolt = 1.6021766208e-19

1.6021766e-19 J


Elementary (electron) charge in Coulomb; ElectronVolt

astroconst.enGrChar = array(['alpha', 'beta', 'gamma', 'delta', 'epsilon', 'zeta', 'eta',        'theta', 'iota', 'kappa', 'lambda', 'mu', 'nu', 'xi', 'omicron',        'pi', 'rho', 'sigma', 'tau', 'upsilon', 'phi', 'chi', 'psi',        'omega'], dtype='<U7')

Lower-case English names for Greek characters.

astroconst.eps0 = 0.409092599824881

Obliquity of the ecliptic in J2000.0, degrees -> radians

astroconst.eps2000 = 0.409092804

Obliquity of the ecliptic at J2000.0 (radians)

astroconst.g = 6.67428e-11

Newton’s gravitational constant

astroconst.glon_se_2000 = 0.5747704

32.93192° in rad


Galactic longitude of the Spring equinox for J2000 = 9.80665

Mean gravitational acceleration at the Earth’s surface, m s^-2

astroconst.h2d = 15.0

Factor to convert hours to degrees

astroconst.h2r = 0.2617993877991494

Factor to convert hours to radians.

astroconst.h_bar = 1.0545718001391127e-34

Reduced Planck constant, J s

astroconst.h_p = 6.62607004e-34

Planck’s constant, 6.6260755e-34 J s

astroconst.htmlGrChar = array(['&alpha;', '&beta;', '&gamma;', '&delta;', '&epsilon;', '&zeta;',        '&eta;', '&theta;', '&iota;', '&kappa;', '&lambda;', '&mu;',        '&nu;', '&xi;', '&omicron;', '&pi;', '&rho;', '&sigma;', '&tau;',        '&upsilon;', '&phi;', '&chi;', '&psi;', '&omega;'], dtype='<U9')

HTML codes for lower-case Greek characters.

astroconst.jd1820 = 2385801

JD in 1820 (when ΔT=0)

astroconst.jd1875 = 2405890

JD at J1875.0 (when constellation boundaries were defined)

astroconst.jd1900 = 2415021

JD at J1900.0

astroconst.jd1950 = 2433283

JD at J1950.0

astroconst.jd2000 = 2451545

00 UT)


JD at J2000.0 (2000-01-01 12

astroconst.k_b = 1.38064852e-23

Boltzmann constant, 1.380658e-23 J/K = 1000.0

Kilometer in SI (m)

astroconst.l_sun = 3.85e+26

Solar luminosity in SI (W)

astroconst.m_h = 1.673532757988e-27

Mass of a hydrogen atom

astroconst.m_sun = 1.9891e+30

Solar mass in SI (kg)

astroconst.mas2r = 4.84813681109536e-09

Factor to convert milliarcseconds to radians.

astroconst.mlen = array([31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31])

Length of the months (for non-leap year). = 0.001

Millimeter in SI (m)

astroconst.month = 2629748.16

Default month == Gregorian month in seconds.

astroconst.month_ano = 2380713.1094592

apside to apside, for J2000.0.


Anomalistic month in seconds

astroconst.month_drac = 2351135.8785888

node to node, for J2000.0.


Draconic month in seconds

astroconst.month_greg = 2629748.16

average calendar month length of 4800 months over 400 years.


Gregorian month in seconds

astroconst.month_sid = 2360591.5576608

fixed star to fixed star, for J2000.0.


Sidereal month in seconds

astroconst.month_syn = 2551442.8768992

phase to phase, for J2000.0.


Synodic month in seconds

astroconst.month_trop = 2360584.7056224

equinox to equinox, influenced by precession, for J2000.0.


Tropical month in seconds

astroconst.months_en = array(['', 'January', 'February', 'March', 'April', 'May', 'June', 'July',        'August', 'September', 'October', 'November', 'December'],       dtype='<U9')

Capitalised month names in English.

astroconst.months_en_abr = array(['', 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep',        'Oct', 'Nov', 'Dec'], dtype='<U3')

Capitalised month abbreviations in English.

astroconst.months_en_abr_lc = array(['', 'jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep',        'oct', 'nov', 'dec'], dtype='<U3')

Lower-case month abbreviations in English.

astroconst.months_en_lc = array(['', 'january', 'february', 'march', 'april', 'may', 'june', 'july',        'august', 'september', 'october', 'november', 'december'],       dtype='<U9')

Lower-case month names in English.

astroconst.months_nl = array(['', 'januari', 'februari', 'maart', 'april', 'mei', 'juni', 'juli',        'augustus', 'september', 'oktober', 'november', 'december'],       dtype='<U9')

Lower-case month names in Dutch.

astroconst.months_nl_abr = array(['', 'jan', 'feb', 'mrt', 'apr', 'mei', 'jun', 'jul', 'aug', 'sep',        'okt', 'nov', 'dec'], dtype='<U3')

Lower-case month abbreviations in Dutch.

astroconst.months_nl_abr_cap = array(['', 'Jan', 'Feb', 'Mrt', 'Apr', 'Mei', 'Jun', 'Jul', 'Aug', 'Sep',        'Okt', 'Nov', 'Dec'], dtype='<U3')

Capitalised month abbreviations in Dutch.

astroconst.months_nl_cap = array(['', 'Januari', 'Februari', 'Maart', 'April', 'Mei', 'Juni', 'Juli',        'Augustus', 'September', 'Oktober', 'November', 'December'],       dtype='<U9')

Capitalised month names in Dutch.

astroconst.moonphase_en = array(['New Moon', 'First Quarter', 'Full Moon', 'Last Quarter'],       dtype='<U13')

English names of Lunar phases.

astroconst.moonphase_nl = array(['Nieuwe Maan', 'Eerste Kwartier', 'Volle Maan', 'Laatste Kwartier'],       dtype='<U16')

Dutch names of Lunar phases.

astroconst.mum = 1e-06

Micrometer in SI (m)

astroconst.nm = 1e-09

Nanometer in SI (m)

astroconst.pi = 3.141592653589793


astroconst.pi2 = 6.283185307179586

astroconst.pio2 = 1.5707963267948966


astroconst.pio4 = 0.7853981633974483


astroconst.pl_a = array([3.84400000e+08, 5.79093357e+10, 1.08204140e+11, 1.49597871e+11,        2.27942276e+11, 7.78327802e+11, 1.42698417e+12, 2.87093274e+12,        4.49706159e+12, 5.91345423e+12])

Planet semi-major axes (m); [0]=Moon

astroconst.pl_d = array([3.47620600e+06, 4.87940000e+06, 1.21980000e+07, 1.27562732e+07,        6.79240000e+06, 1.42984000e+08, 1.20536000e+08, 5.11180000e+07,        4.95280000e+07, 2.39000000e+06])

Equatorial planet diameters (m); [0]=Moon; Venus = 12103.6km + clouds?

astroconst.pl_p = array([2.36045800e+06, 7.60035920e+06, 1.94137573e+07, 3.15569252e+07,        5.93528960e+07, 3.74328247e+08, 9.29575501e+08, 2.65142863e+09,        5.20058127e+09, 7.82422403e+09])

//; [0]=Moon.


Planet orbital periods (s - https

astroconst.pl_r = array([ 1738103. ,  2439700. ,  6099000. ,  6378136.6,  3396200. ,        71492000. , 60268000. , 25559000. , 24764000. ,  1195000. ])

Planet equatorial radii (m) = pland/2.

astroconst.plname_en = array(['Moon', 'Mercury', 'Venus', 'Sun', 'Mars', 'Jupiter', 'Saturn',        'Uranus', 'Neptune', 'Pluto'], dtype='<U7')

Capitalised planet names.

astroconst.plname_en_abr = array(['Moon', 'Mer.', 'Ven.', 'Sun', 'Mars', 'Jup.', 'Sat.', 'Ura.',        'Nep.', 'Plu.'], dtype='<U4')

Capitalised planet abbreviations.

astroconst.plname_en_lc = array(['moon', 'mercury', 'venus', 'sun', 'mars', 'jupiter', 'saturn',        'uranus', 'neptune', 'pluto'], dtype='<U7')

Lower-case planet names.

astroconst.plname_nl = array(['Maan', 'Mercurius', 'Venus', 'Zon', 'Mars', 'Jupiter', 'Saturnus',        'Uranus', 'Neptunus', 'Pluto'], dtype='<U9')

Capitalised Dutch planet names.

astroconst.plname_nl_abr = array(['Maan', 'Mer.', 'Ven.', 'Zon', 'Mars', 'Jup.', 'Sat.', 'Ura.',        'Nep.', 'Plu.'], dtype='<U4')

Capitalised Dutch planet abbreviations.

astroconst.plname_nl_lc = array(['maan', 'mercurius', 'venus', 'zon', 'mars', 'jupiter', 'saturnus',        'uranus', 'neptunus', 'pluto'], dtype='<U9')

Lower-case Dutch planet names.

astroconst.r2am = 3437.7467707849396

Factor to convert radians to arcminutes

astroconst.r2as = 206264.80624709636

Factor to convert radians to arcseconds.

astroconst.r2d = 57.29577951308232

Factor to convert radians to degrees.

astroconst.r2h = 3.819718634205488

Factor to convert radians to hours.

astroconst.r2mas = 206264806.24709636

Factor to convert radians to milliarcseconds.

astroconst.r_earth = 6378136.6

Equatorial radius of the Earth in SI (m), WGS84

astroconst.r_sun = 695990000.0

Solar radius in SI (m)

astroconst.ra_gp_2000 = 3.3660329

192.85948° in rad


RA of the Galactic pole for J2000

astroconst.sigma = 5.6703668160832706e-08

Stefan-Boltzmann constant, 5.67051e-8 J m^-2 K^-4 s^-1

astroconst.sol_const = 1361.5

Solar constant in W/m^2 (Wikipedia)

astroconst.year = 31556925.187488

Default year == tropical year (s), for J2000.0.

astroconst.year_anom = 31558432.5386496

apside to apside, for J2000.0


Anomalistic year in seconds

astroconst.year_greg = 31556952.0

assumes 97 leap years in 400 years, for J2000.0


Gregorian year in seconds

astroconst.year_jul = 31557600.0

assumes 100 leap years in 400 years, for J2000.0


Julian year in seconds

astroconst.year_sid = 31558149.7676064

fixed star to fixed star, for J2000.0


Siderial year in seconds

astroconst.year_trop = 31556925.187488

equinox to equinox, influenced by precession, for J2000.0


Tropical year in seconds