astro function

Calculations for position of the sun and moon

This set of functions provides simple position calculations for the sun and moon, taken from Pascal routines published in Montenbruck and Pfleger (1994, Dunlop).

These are completely independent from the (specifically optimized) solar elevation calculations available via [elevation and solar].

astro(lon, lat, astro.calc)

EQUHOR(DEC, TAU, PHI)

FRAC(x)

LMST(MJDay, LAMBDA)

lunar(time)

mini.sun(time)

MJD(date)

POLAR(X, Y, Z)

Arguments

• lon: vector of longitudes

• lat: vector of latitudes

• astro.calc: list object containing RA right ascension

• DEC: declination

• TAU: TAU

• PHI: PHI

• x: number

• MJDay: modified julian day

• LAMBDA: LAMBDA

• time: vector of date-times in POSIXct format

• date: vector of date-times in POSIXct format

• X: x-coordinate

• Y: y-coordinate

• Z: z-coordinate

Returns

astro returns a list object with the components of the moon or sun's position, - r: rho component

• theta: theta component - elevation

• phi: phi component - azimuth

References

@BOOK{,
  title = {Astronomy on the Personal Computer},
  publisher = {Springer-Verlag, Berlin},
  year = {1994},
  author = {Oliver Montenbruck and Thomas Pfleger},
  edition = {2  (translated from German by Storm Dunlop)},
}

Author(s)

Michael D. Sumner

Note

Thanks to Nick.Ellis@csiro.au for pointing out a mistake pre-0.0-27

Warning

Some of this could be faster (particularly the use of LMST in "astro" is not precalculated)

See Also

See Also elevation

Examples

## the moon
tm <- Sys.time() + seq(by = 3600, length = 100)
moon <- lunar(tm)
rtp <- astro(147, -42, moon)
op <- par(mfrow = c(2,1))
plot(tm, rtp$theta, main = "lunar elevation, Hobart")
plot(tm, rtp$phi, main = "lunar azimuth, Hobart")
par(op)

## the sun
tm <- Sys.time() + seq(by = 3600, length = 100)
sun <- mini.sun(tm)
rtp <- astro(147, -42, sun)
op <- par(mfrow = c(2,1))
plot(tm, rtp$theta, main = "solar elevation, Hobart")
plot(tm, rtp$phi, main = "solar azimuth, Hobart")
par(op)
  elev.gmt <- mkElevationSeg(1, tm)
  plot(tm, rtp$theta, main = "solar elevation mini.sun versus NOAA")
  lines(tm, elev.gmt(1, 147, -42))