nutate {astrolibR} R Documentation

## Calculate the nutation in longitude and obliquity for a given Julian date

### Description

Calculate the nutation in longitude and obliquity for a given Julian date

### Usage

```nutate(jd)
```

### Arguments

 `jd` Julian ephemeris date, scalar or vector

### Details

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".

### Value

 `nut_long` nutation in longitude, same number of elements as jd `nut_obliq` nutation in latitude, same number of elements as jd

### Author(s)

Written, W. Landsman 1992

R adaptation by Arnab Chakraborty June 2013

### References

Meeus, J., 1998, “Astronomical Algorithms”, 2nd ed.

`cirrange` `polyidl`

### Examples

```# 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)')
```

[Package astrolibR version 0.1 Index]