nutate {astrolibR} | R Documentation |
Calculate the nutation in longitude and obliquity for a given Julian date
nutate(jd)
jd |
Julian ephemeris date, scalar or vector |
This function uses the formula in Meuss (1998, Chpt. 22) which is based on the 1980 IAU Theory of Nutation and includes all terms larger than 0.0003".
nut_long |
nutation in longitude, same number of elements as jd |
nut_obliq |
nutation in latitude, same number of elements as jd |
Written, W. Landsman 1992
R adaptation by Arnab Chakraborty June 2013
Meeus, J., 1998, “Astronomical Algorithms”, 2nd ed.
# Find the nutation in longitude and obliquity 1987 on Apr 10 at Oh. # Result: nut_long = -3.788 nut_obliq = 9.443 # This is example 22.a from Meeus jul = jdcnv(1987,4,10,0) nutate(jul) # Plot the large-scale variation of the nutation in longitude # during the 20th century. This plot will reveal the dominant 18.6 year # period, but a finer grid is needed to display the shorter periods in # the nutation. yr = 1900 + seq(0,100) # establish sequence of years jul = jdcnv(yr,1,1,0) # find Julian date of first day of year out = nutate(jul) # compute nutation plot(yr, out$nut_long, lty=1, lwd=2, xlab='Year', ylab='Nutation longitude (degrees)')