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Ephem

Description

ephem is a wrapper for libnova a "general purpose, double precision, Celestial Mechanics, Astrometry and Astrodynamics library."

Author

Rob Altenburg

Requirements

numbers, srfi-19, foreigners

Installation

ephem requires libnova v0.16. That version is available from the git repository.

Procedures

The libnova modules documentation provides essential details. Main differences from that library are:

• ephem function names are separated with dashes instead of underscores and the "ln" or "ln_get" prefix is omitted.
• ephem functions are not passed structures to hold results--when necessary they allocate and return a new object of the required foreign type.
• srfi-19 date functions are used instead of equivalent libnova functions.

Data Types

Rise, Set, Transit

make-rst #!optional rise set transitprocedure

Returns a ln_rst_time foreign record type. If rise, set, or transit is not specified an empty structure is allocated and returned.

Rise, set, and transit are Julian dates as returned by srfi-19's (date->julian-day) function.

Note that I didn't expose the setters to mutate existing records of a given type.

rst-rise rstprocedure

rst-set rstprocedure

rst-transit rstprocedure

Rectangular Coordinates

make-rect #!optional x y xprocedure

rect-x rectprocedure

rect-y rectprocedure

rect-z rectprocedure

Heliocentric Coordinates

make-helio #!optional l b rprocedure

helio-l helioprocedure

helio-b helioprocedure

helio-r helioprocedure

Longitude and Latitude

make-ecl #!optional longitude latitudeprocedure

ecl-lng eclprocedure

ecl-lat eclprocedure

Equatorial Coordinates

make-equ #!optional ra decprocedure

Note: Right ascension and declination are both expressed in degrees, right ascensions given in h:m:s must be converted:

(hms->deg 12 30 1)

equ-ra equprocedure

equ-dec equprocedure

Horizontal Coordinates

make-hrz #!optional azimuth altitudeprocedure

hrz-az hrzprocedure

hrz-alt hrzprocedure

Hours, Minutes, Seconds

make-hms #!optional hours minuts secondsprocedure

hms-hours hmsprocedure

hms-minutes hmsprocedure

hms-seconds hmsprocedure

Nutation

make-nutation #!optional longitude obliquity eclipticprocedure

nutation-longitude nutationprocedure

nutation-obliquity nutationprocedure

nutation-ecliptic nutationprocedure

Orbital Elements

Elliptic Orbital Elements

make-ell #!optional a e i w omega n jdprocedure

ell-a ellprocedure

ell-e ellprocedure

ell-i ellprocedure

ell-w ellprocedure

ell-omega ellprocedure

ell-n ellprocedure

ell-jd ellprocedure

Hyperbolic Orbital Elements

make-hyp #!optional q e i w omega jdprocedure

hyp-q hypprocedure

hyp-e hypprocedure

hyp-i hypprocedure

hyp-w hypprocedure

hyp-omega hypprocedure

hyp-jd hypprocedure

Parabolic Orbital Elements

make-par #!optional q i w omega jdprocedure

par-q parprocedure

par-i parprocedure

par-w parprocedure

par-omega parprocedure

par-jd parprocedure

Sidereal Time

gmst jdprocedure

gast jdprocedure

lmst jd longitudeprocedure

last jd longitudeprocedure

Utility

get-versionprocedure

rad->deg radprocedure

deg->rad degprocedure

hms->deg hmsprocedure

deg->hms degprocedure

get-dateprocedure

vsop87->fk5 helio jdprocedure

Rise, Set, Transit

object-rst jd ecl-observer equ-objectprocedure

object-next-rst jd ecl-observer equ-objectprocedure

object-next-rst-horizon jd ecl-observer equ-object horizonprocedure

body-rst-horizon jd ecl-observer body-object horizonprocedure

body-next-rst-horizon jd ecl-observer body-object horizonprocedure

body-next-rst-horizon-future jd ecl-observer body-object horizon day-limitprocedure

Motion

Elliptic Motion

solve-kepler e Mprocedure

ell-mean-anomaly n delta-jdprocedure

ell-true-anomaly e Eprocedure

ell-radius-vector a e Eprocedure

ell-smajor-diam e qprocedure

ell-sminor-diam e aprocedure

ell-mean-motion aprocedure

ell-geo-rect-posn ell jdprocedure

ell-helio-rect-posn ell jdprocedure

ell-orbit-len ellprocedure

ell-orbit-vel jd ellprocedure

ell-orbit-pvel ellprocedure

ell-orbit-avel ellprocedure

ell-body-phase-angle jd ellprocedure

ell-body-elong jd ellprocedure

ell-body-solar-dist jd ellprocedure

ell-body-earth-dist jd ellprocedure

ell-body-equ-coords jd ellprocedure

ell-body-rst jd eclprocedure

ell-body-rst-horizon jd ecl ell horizonprocedure

ell-body-next-rst-horizon jd ecl ell horizonprocedure

ell-body-next-rst-horizon-future jd ecl ell horizon day-limitprocedure

ell-last-perihelion epoch-jd M nprocedure

Hyperbolic Motion

solve-hyp-barker Q1 G tprocedure

hyp-true-anomaly q e tprocedure

hyp-radius-vector q e tprocedure

hyp-geo-rect-posn hprocedure

hyp-helio-rect-posn hyp jdprocedure

hyp-body-equ-coords jd hypprocedure

hyp-body-earth-dist jd hypprocedure

hyp-body-solar-dist jd hypprocedure

hyp-body-phase-angle jd hypprocedure

hyp-body-elong jd hypprocedure

hyp-body-rst jd ecl hypprocedure

hyp-body-rst-horizon jd ecl hyp horizonprocedure

hyp-body-next-rst-horizon jd ecl hyp horizonprocedure

hyp-body-next-rst-horizon-future jd ecl hyp horizon day-limitprocedure

Parabolic Motion

solve-barker q tprocedure

par-true-anomaly q tprocedure

par-radius-vector q tprocedure

par-geo-rect-posn par jdprocedure

par-helio-rect-posn par jdprocedure

par-body-equ-coords jd parprocedure

par-body-earth-dist jd parprocedure

par-body-solar-dist jd parprocedure

par-body-phase-angle jd parprocedure

par-body-elong jd parprocedure

par-body-rst jd ecl parprocedure

par-body-rst-horizon jd ecl par horizonprocedure

par-body-next-rst-horizon jd ecl par horizonprocedure

par-body-next-rst-horizon-future jd ecl par horizon day-limitprocedure

Bodies

Sun

solar-rst-horizon jd ecl horizonprocedure

solar-rst jd eclprocedure

solar-geom-coords jdprocedure

solar-equ-coords jdprocedure

solar-ecl-coords jdprocedure

solar-geo-coords jdprocedure

solar-sdiam jdprocedure

Earth

earth-helio-coords jdprocedure

earth-solar-dist jdprocedure

earth-rect-helio jdprocedure

earth-centre-dist height latitudeprocedure

Moon

lunar-phase jdprocedure

lunar-disk jdprocedure

lunar-sdiam jdprocedure

lunar-earth-dist jdprocedure

lunar-bright-limb jdprocedure

lunar-long-asc-node jdprocedure

lunar-long-perigee jdprocedure

lunar-equ-coords jd precisionprocedure

lunar-rst jd eclprocedure

lunar-geo-posn jd precisionprocedure

lunar-equ-coords-prec jd precisionprocedure

lunar-ecl-coords jd precisionprocedure

Mercury

mercury-sdiam jdprocedure

mercury-rst jd eclprocedure

mercury-helio-coords jdprocedure

mercury-equ-coords jdprocedure

mercury-earth-dist jdprocedure

mercury-solar-dist jdprocedure

mercury-magnitude jdprocedure

mercury-disk jdprocedure

mercury-phase jdprocedure

mercury-rect-helio jdprocedure

Venus

venus-sdiam jdprocedure

venus-rst jd eclprocedure

venus-helio-coords jdprocedure

venus-equ-coords jdprocedure

venus-earth-dist jdprocedure

venus-solar-dist jdprocedure

venus-magnitude jdprocedure

venus-disk jdprocedure

venus-phase jdprocedure

venus-rect-helio jdprocedure

Mars

mars-sdiam jdprocedure

mars-rst jd eclprocedure

mars-helio-coords jdprocedure

mars-equ-coords jdprocedure

mars-earth-dist jdprocedure

mars-solar-dist jdprocedure

mars-magnitude jdprocedure

mars-disk jdprocedure

mars-phase jdprocedure

mars-rect-helio jdprocedure

Jupiter

jupiter-equ-sdiam jdprocedure

jupiter-pol-sdiam jdprocedure

jupiter-rst jd eclprocedure

jupiter-helio-coords jdprocedure

jupiter-equ-coords jdprocedure

jupiter-earth-dist jdprocedure

jupiter-solar-dist jdprocedure

jupiter-magnitude jdprocedure

jupiter-disk jdprocedure

jupiter-phase jdprocedure

jupiter-rect-helio jdprocedure

Saturn

saturn-equ-sdiam jdprocedure

saturn-pol-sdiam jdprocedure

saturn-rst jd eclprocedure

saturn-helio-coords jdprocedure

saturn-equ-coords jdprocedure

saturn-earth-dist jdprocedure

saturn-solar-dist jdprocedure

saturn-magnitude jdprocedure

saturn-disk jdprocedure

saturn-phase jdprocedure

saturn-rect-helio jdprocedure

Uranus

uranus-sdiam jdprocedure

uranus-rst jd eclprocedure

uranus-helio-coords jdprocedure

uranus-equ-coords jdprocedure

uranus-earth-dist jdprocedure

uranus-solar-dist jdprocedure

uranus-magnitude jdprocedure

uranus-disk jdprocedure

uranus-phase jdprocedure

uranus-rect-helio jdprocedure

Neptune

neptune-sdiam jdprocedure

neptune-rst jd eclprocedure

neptune-helio-coords jdprocedure

neptune-equ-coords jdprocedure

neptune-earth-dist jdprocedure

neptune-solar-dist jdprocedure

neptune-magnitude jdprocedure

neptune-disk jdprocedure

neptune-phase jdprocedure

neptune-rect-helio jdprocedure

Pluto

pluto-sdiam jdprocedure

pluto-rst jd eclprocedure

pluto-helio-coords jdprocedure

pluto-equ-coords jdprocedure

pluto-earth-dist jdprocedure

pluto-solar-dist jdprocedure

pluto-magnitude jdprocedure

pluto-disk jdprocedure

pluto-phase jdprocedure

pluto-rect-helio jdprocedure

Misc

heliocentric-time-diff jd equprocedure

refraction-adj altitude atm-pressure tempprocedure

equ-aberration equ jdprocedure

ecl-aberration equ jdprocedure

dynamical-time-diff jdeprocedure

jde jdprocedure

angular-separation equ equprocedure

rel-posn-angle equ equprocedure

constellationprocedure

apparent-posn equ-mean equ-proper jdprocedure

nutation jdprocedure

equ-prec equ-mean jdprocedure

equ-prec2 equ-mean jd jdprocedure

ecl-prec ecl jdprocedure

ell-comet-mag jd ell g kprocedure

par-comet-mag jd par g kprocedure

Transforms

hrz-from-equ equ ecl jdprocedure

hrz-from-equ-sidereal-time equ ecl siderealprocedure

equ-from-ecl ecl jdprocedure

ecl-from-equ equ jdprocedure

rect-from-helio helioprocedure

ecl-from-rect rectprocedure

equ-from-gal galprocedure

equ2000-from-gal galprocedure

gal-from-equ equprocedure

gal-from-equ2000 equprocedure

Non-Libnova

range-hours hoursprocedure

range-degrees degreesprocedure

range-degrees180 degreesprocedure

is-above-horizon? equ ecl jdprocedure

dms->deg dmsprocedure

hms->hr hmsprocedure

Examples

(use numbers srfi-19 ephem)

; set time using srfi-19
(define dd (exact->inexact (date->julian-day 
                             (make-date 0 0 30 7 13 12 2016 (* 3600 0)  #f))))

; set the longitude and latitude of the observer
(define my-ecl (make-ecl -76.8867 40.2732))

; calculate the Sun's rise, set, and transit using different methods
(define rst (solar-rst dd my-ecl))

; print the Julian date of the rise time
(display (rst-rise rst))
(newline)

License

LGPL-3.0

Version History

1.0 Initial Release