# nutate: Calculate the nutation in longitude and obliquity for a given... In astrolibR: Astronomy Users Library

## Description

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

## Usage

 `1` ```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

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17``` ```# 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)') ```

### Example output

```\$nut_long
[1] -3.593116

\$nut_obliq
[1] 9.641048

Warning messages:
1: In d * d_lng :
longer object length is not a multiple of shorter object length
2: In m * m_lng :
longer object length is not a multiple of shorter object length
3: In mprime * mp_lng :
longer object length is not a multiple of shorter object length
4: In f * f_lng :
longer object length is not a multiple of shorter object length
5: In omega * om_lng :
longer object length is not a multiple of shorter object length
```

astrolibR documentation built on May 29, 2017, 4:34 p.m.