helio {astrolibR} | R Documentation |
Compute (low-precision) heliocentric coordinates for the planets
helio(jd, list1, radian=FALSE)
jd |
Julian date, scalar or vector |
list1 |
List of planets array. May be a single number. 1 = merc, 2 = venus, ... 9 = pluto |
radian |
If =TRUE, then the output longitude and latitude are given in radians. If =FALSE, the output are in degrees. (default=FALSE) |
The mean orbital elements for epoch J2000 are used. These are derived from a 250 yr least squares fit of the DE 200 planetary ephemeris to a Keplerian orbit where each element is allowed to vary linearly with time. For dates between 1800 and 2050, this solution fits the terrestrial planet orbits to ~25" or better, but achieves only ~600" precision for Saturn.
These output arrays are dimensioned Nplanet x Ndate, where Nplanet is the number of elements of list1, and Ndate is the number of elements of Jjd.
Use planet_coords (which calls helio) to get celestial (RA, Dec) coordinates of the planets
hrad |
array of heliocentric radii, in Astronomical Units |
hlong |
array of heliocentric (ecliptic) longitudes, in degrees or radians |
hlat |
array of heliocentric latitudes, in degrees or radians |
R. Sterner 1986 and W. Landsman 2000
R adaptation by Arnab Chakraborty June 2013
# (1) Find the current heliocentric positions of all the planets jd_today <- 2456877.5 helio(jd_today,seq(1,9)) # (2) Find heliocentric position of Mars on August 23, 2000 # Result: hrad = 1.6407 AU hlong = 124.3197 hlat = 1.7853 # For comparison, the JPL ephemeris gives hrad = 1.6407 AU hlong = 124.2985 hlat = 1.7845 helio(2451779.5,4)