astrolibR (version 0.1)

rhotheta: Calculate the separation and position angle of a binary star

Description

Calculate the separation and position angle of a binary star

Usage

rhotheta(p, t, e, a, i, omega, omega2, t2)

Arguments

p

period (scalar, year)

t

time of periastron passage (scalar, year)

e

orbit eccentricity (scalar between 0 and 1)

a

semi-major axis (scalar, arc second)

i

scalar, inclination

omega

node (scalar, degree)

omega2

longitude of periastron (scalar, degree)

t2

epoch of observation (scalar, year)

Value

An R list with two scalar elements: \

rho

separation (arcsec)

theta

position angle measured east of north (degree)

In case of errors, rho and theta are returned as -1.

Details

This function will return the separation rho and position angle theta of a visual binary star derived from its orbital elements. The algorithm is from Meuss (1992; also 1998).

References

Meeus J., 1992, Astronomische Algorithmen, Barth. Meeus, J., 1998, ``Astronomical Algorithms'', 2nd ed.

Examples

#  Find the position of Eta Coronae Borealis at the epoch 1980.0
#  Result:   rho=     0.411014    theta=       318.42307
rhotheta(41.623, 1934.008, 0.2763, 0.907, 59.025, 23.717, 219.907, 1980.0)