helio_jd {astrolibR} | R Documentation |
Convert geocentric (reduced) Julian date to heliocentric Julian date
helio_jd(date, ra, dec, B1950=FALSE, time_diff=FALSE)
date |
reduced Julian date (= JD - 2400000), scalar or vector |
ra,dec |
scalars giving right ascension and declination, in degrees |
B1950 |
If =FALSE, equinox is J2000, if =TRUE, equinox is B1950 (default = FALSE) |
time_diff |
If =TRUE, then the function returns the time difference (heliocentric JD - geocentric JD), in seconds (default=FALSE) |
This procedure correct for the extra light travel time between the Earth and the Sun. An online calculator for this quantity is available at http://www.physics.sfasu.edu/astro/javascript/hjd.html. Users requiring more precise calculations and documentation should look at the IDL code available at http://astroutils.astronomy.ohio-state.edu/time/. The algorithm here is from Henden and Kaitchuck (1982, p.114).
jdhelio |
heliocentric reduced Julian date (but see time_diff) |
Written by W. Landsman STX 1989
R adaptation by Arnab Chakraborty June 2013
Henden, A. A. and Kaitchuck, R. H., 1982, "Astronomical Photometry", Van Nostrand Reinhold
# What is the heliocentric Julian date of an observation of V402 Cygni # (J2000: RA = 20 9 7.8, Dec = 37 09 07) taken June 15, 1973 at 11:40 UT? # Result: hjd = 41848.9881 jd <- juldate(c(1973,6,15,11,40)) # Get geocentric Julian date hjd <- helio_jd(jd, ten(20,9,7.8)*15., ten(37,9,7))