Section 8: Delta T-related functions

Functions related to DeltaT and tidal acceleration

swe_deltat_ex(jd_ut, ephe_flag)

swe_deltat(jd_ut)

swe_set_tid_acc(t_acc)

swe_get_tid_acc()

swe_set_delta_t_userdef(delta_t)

Arguments

jd_ut

Julian day number (UT) as numeric vector (day)

ephe_flag

ephemeris flag as integer (SE$FLG_JPLEPH=1, SE$FLG_SWIEPH=2 or SE$FLG_MOSEPH=4)

t_acc

Tidal acceleration as double (arcsec/century^2)

delta_t

DeltaT (day)

Value

swe_deltat_ex returns a list with named entries: deltat for DeltaT as double (day) and serr for error message as string.

swe_deltat returns the DeltaT as double (day)

swe_get_tid_acc returns the tidal acceleration as double (arcsec/century^2)

Details

swe_deltat_ex()

Determine DeltaT from Julian day number for a specific ephemeris.

swe_deltat()

Determine DeltaT from Julian day number for a used ephemeris. This function is only safe if:

• your software consistently uses the same ephemeris flag

• if software consistently uses the same ephemeris files (with SE$FLG_SWIEPH and SE$FLG_MOSEPH)

• if swe_set_ephe_path() is first called (with SE$FLG_SWIEPH) and swe_set_jpl_file() (with SE$FLG_JPLEPH)

swe_set_tid_acc()

Set the tidal acceleration.

swe_get_tid_acc()

Get the present configured tidal acceleration.

swe_set_delta_t_userdef()

Allows the user to set a fixed DeltaT value that will be returned by swe_deltat() or swe_deltat_ex().

See also

Section 8 in http://www.astro.com/swisseph/swephprg.htm. Remember that array indices start in R at 1, while in C they start at 0!

Examples

data(SE)
swe_deltat_ex(1234.567, SE$FLG_MOSEPH)
#> $deltat
#> [1] 1.587386
#> 
#> $serr
#> [1] ""
#> 
swe_deltat(1234.567)
#> [1] 1.597676
swe_set_tid_acc(1.23)
swe_get_tid_acc()
#> [1] 1.23
swe_set_delta_t_userdef(0.23)