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# NAME

Astro::Montenbruck::NutEqu - Obliquity of the ecliptic & nutation.

# SYNOPSIS

`````` # given mean geocentric coordinates \$x0, \$y0, \$z0,
# transform them to apparent coordinates \$x1, \$y1, \$z1
my \$func = nutequ( \$t );
(\$x1, \$y1, \$z1) = \$func->(\$x0, \$y0, \$z0); # true coordinates``````

# DESCRIPTION

Functions dealing with ecliptic obliquity.

# SUBROUTINES

## deltas( \$t )

Calculates the effects of nutation on the ecliptic longitude and on the obliquity of the ecliptic with accuracy of about 1 arcsecond. Given time in Julian centuries since J2000, return delta-psi and delta-eps.

### Arguments

• \$t — time in Julian centuries since J2000: `(JD-2451545.0)/36525.0`

### Returns

`(\$delta_psi, \$delta_eps)`, in arc-degrees.

## mean2true(\$t)

Returns function for transforming of mean to true coordinates.

### Arguments

• \$t — time in Julian centuries since J2000: `(JD-2451545.0)/36525.0`

### Returns

Function which takes mean ecliptic geocentric rectangular coordinates `X, Y, Z` of a planet and returns ecliptic rectangular coordinates, referred to the equinox of date.

## obliquity( \$t )

Given time in Julian centuries since J2000, return mean obliquity of the ecliptic, in arc-degrees.

# AUTHOR

Sergey Krushinsky, `<krushi at cpan.org>`