rhotheta {astrolibR} | R Documentation |
Calculate the separation and position angle of a binary star
rhotheta(p, t, e, a, i, omega, omega2, t2)
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) |
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).
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.
Written, Sebastian Kohl, 2012.
R adaptation by Arnab Chakraborty June 2013
Meeus J., 1992, Astronomische Algorithmen, Barth. Meeus, J., 1998, “Astronomical Algorithms”, 2nd ed.
# 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)