R/astronomy.R
angle2hms.RdThe purpose of angle2hms is to facilitate comparison of
rightAscension angles computed by sunAngle() and moonAngle()
with angles reported in astronomical sources and software, which
often employ an hour-minute-second notation. In that notation,
decimal hour is computed as 24/360 times the angle in degrees,
and from that decimal hour are compute integer hour and minute
values, plus a decimal second value. It is common in the
astronomical literature to use strings to represent the results,
e.g. with \(11^h40^m48^s.10\) for the
value used in the “Examples”; see Chapter 1 of
Meeus (1991) for more on angle calculation and representation.
angle2hms(angle)numerical value giving an angle in degrees
angle2hms returns a list containing
values time (a numerical value for decimal hour, between 0 and 24),
hour, minute, and second (the last of which may have a fractional
part), and string, a character value indicates the time in hour-minute-second
notation, with the second part to two decimal places and intervening h,
m and s characters between the units.
Meeus, Jean. Astronomical Algorithms. Second Edition. Richmond, Virginia, USA: Willmann-Bell, 1991.
Other things related to astronomy:
eclipticalToEquatorial(),
equatorialToLocalHorizontal(),
julianCenturyAnomaly(),
julianDay(),
moonAngle(),
siderealTime(),
sunAngle(),
sunDeclinationRightAscension()
# A randomly-chosen example on page 99 of Meeus (1991).
angle2hms(177.74208) # string component 11h50m58s.10
#> $hourDecimal
#> [1] 11.84947
#>
#> $hour
#> [1] 11
#>
#> $minute
#> [1] 50
#>
#> $second
#> [1] 58.0992
#>
#> $string
#> [1] "11h50m58s.10"
#>