NAME

DateTime::Util::Astro::Common - Common Utilities For Astronomical Calendar Calculations

SYNOPSIS

  use DateTime::Util::Astro::Common qw(
    aberration
    dt_from_dynamical
    dynamical_moment_from_dt
    ephemeris_correction
    equation_of_time
    julian_centuries
    local_from_apparent 
    nutation
    obliquity
    standard_from_local
    standard_from_universal
    universal_from_local
    universal_from_standard
    SPRING
    SUMMER
    AUTUMN
    WINTER
    MEAN_TROPICAL_YEAR
    RD_MOMENT_1900_JAN_1
    RD_MOMENT_1810_JAN_1
    RD_MOMENT_J2000
  );

  my $location = DateTime::Util::Astro::Location->new(
    longitude => $longitude,
    latitude  => $latitude,
    zone      => $zone,
    elevation => $elevation
  );

DESCRIPTION

DateTime::Util::Astro::Location implements some functions that are commonly used for astronomical calculations. As with other DateTime::Util::Astro:: modules this module only implements the bare minimum required to make astronomical calendars.

FUNCTIONS

aberration($dt)

Calculates the effect of the sun's moving during the time its light takes takes to reach the Earth

dt_from_dynamical($moment)

dynamical_moment_from_dt($dt)

julian_centuries($moment)

The number and fraction of uniform-length centuries at a given moment.

ephemeris_correction($dt)

Calculates the offset from "dynamical time", which is caused by the retarding effects of tide and other atmospheric conditions.

EC_C

EC_X

EC1

EC2

EC3

EC4

EC5

EC6

These are used to calculate the ephemeris_correction.

equation_of_time($dt)

Calculates the difference between "apparent midnight" and the "mean midnight"

julian_centuris($dt)

Calculates the fractional number of centuries since January 1, 2000 (Gregorian).

local_from_apparent($dt)

nutation($dt)

Calculates the effect caused by the wobble of the Earth.

obliquity($)

Calculates the inclination of th Earth

local_from_standard($dt, $location)

local_from_universal($dt, $location)

standard_from_local($dt,$location)

standard_from_universal($dt,$location)

universal_from_local($dt,$location)

universal_from_standard($dt,$location)

CONSTANTS

SPRING

SUMMER

AUTUMN

WINTER

The solar longitude for equinoxes and solstices.

MEAN_TROPICAL_YEAR

The time it takes for the mean sun to return to the same position relative to the celestial equator

RD_MOMENT_1900_JAN_1

RD_MOMENT_1810_JAN_1

RD_MOMENT_J2000

TODO

DateTime::Util::Astro::Location probably isn't worth existing, as I believe the math involved with locations can probably be done via DateTime itself, or at least via DateTime::Locale and DateTime::TimeZone objects.

Hence it is foraseeable that DateTime::Util::Astro::Location will be phased out eventually and I've opted to keep it as a private class within his module, so that it doesn't pollute users' file systems.

AUTHOR

REFERENCES

  [1] Edward M. Reingold, Nachum Dershowitz
      "Calendrical Calculations (Millenium Edition)", 2nd ed.
       Cambridge University Press, Cambridge, UK 2002

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