R: Sun Declination and Right Ascension

sunDeclinationRightAscension {oce} | R Documentation

## Sun Declination and Right Ascension

### Description

The formulae are from Meeus (1991), chapter 24 (which uses chapter 21).

### Usage

    sunDeclinationRightAscension(time, apparent = FALSE)

### Arguments

`time` | a POSIXct time. This ought to be in UTC timezone; if not, the behaviour of this function is unlikely to be correct.
`apparent` | logical value indicating whether to return the 'apparent' angles.

### Value

A list containing `declination` and `rightAscension`, in degrees.

### Author(s)

Dan Kelley, based on formulae in Meeus (1991).

### References

1. Meeus, Jean H. Astronomical Algorithms. Second edition. Willmann-Bell, Incorporated, 1991.

### See Also

Other things related to astronomy: `eclipticalToEquatorial()`, `equatorialToLocalHorizontal()`, `julianCenturyAnomaly()`, `julianDay()`, `moonAngle()`, `siderealTime()`, `sunAngle()`

### Examples

    ## Example 24.a in Meeus (1991) (page 158 PDF, 153 print)
    time <- as.POSIXct("1992-10-13 00:00:00", tz="UTC")
    a <- sunDeclinationRightAscension(time, apparent=TRUE)
    expect_equal(a$declination, -7.78507,
                 tol=            0.00004, scale=1)
    expect_equal(a$rightAscension, -161.61919,
                 tol=                 0.00003, scale=1)
    b <- sunDeclinationRightAscension(time)
    ## check against previous results, to protect aginst code-drift errors
    expect_equal(b$declination, -7.785464443,
                 tol=            0.000000001, scale=1)
    expect_equal(b$rightAscension, -161.6183305,
                 tol=                 0.0000001, scale=1)

[Package oce version 1.2-0 Index]