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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

[procedure] (make-rst #!optional rise set transit)

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.

[procedure] (rst-rise rst)
[procedure] (rst-set rst)
[procedure] (rst-transit rst)

Rectangular Coordinates

[procedure] (make-rect #!optional x y x)
[procedure] (rect-x rect)
[procedure] (rect-y rect)
[procedure] (rect-z rect)

Heliocentric Coordinates

[procedure] (make-helio #!optional l b r)
[procedure] (helio-l helio)
[procedure] (helio-b helio)
[procedure] (helio-r helio)

Longitude and Latitude

[procedure] (make-ecl #!optional longitude latitude)
[procedure] (ecl-lng ecl)
[procedure] (ecl-lat ecl)

Equatorial Coordinates

[procedure] (make-equ #!optional ra dec)

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)

[procedure] (equ-ra equ)
[procedure] (equ-dec equ)

Horizontal Coordinates

[procedure] (make-hrz #!optional azimuth altitude)
[procedure] (hrz-az hrz)
[procedure] (hrz-alt hrz)

Hours, Minutes, Seconds

[procedure] (make-hms #!optional hours minuts seconds)
[procedure] (hms-hours hms)
[procedure] (hms-minutes hms)
[procedure] (hms-seconds hms)

Nutation

[procedure] (make-nutation #!optional longitude obliquity ecliptic)
[procedure] (nutation-longitude nutation)
[procedure] (nutation-obliquity nutation)
[procedure] (nutation-ecliptic nutation)

Orbital Elements

Elliptic Orbital Elements

[procedure] (make-ell #!optional a e i w omega n jd)
[procedure] (ell-a ell)
[procedure] (ell-e ell)
[procedure] (ell-i ell)
[procedure] (ell-w ell)
[procedure] (ell-omega ell)
[procedure] (ell-n ell)
[procedure] (ell-jd ell)

Hyperbolic Orbital Elements

[procedure] (make-hyp #!optional q e i w omega jd)
[procedure] (hyp-q hyp)
[procedure] (hyp-e hyp)
[procedure] (hyp-i hyp)
[procedure] (hyp-w hyp)
[procedure] (hyp-omega hyp)
[procedure] (hyp-jd hyp)

Parabolic Orbital Elements

[procedure] (make-par #!optional q i w omega jd)
[procedure] (par-q par)
[procedure] (par-i par)
[procedure] (par-w par)
[procedure] (par-omega par)
[procedure] (par-jd par)

Sidereal Time

[procedure] (gmst jd)
[procedure] (gast jd)
[procedure] (lmst jd longitude)
[procedure] (last jd longitude)

Utility

[procedure] (get-version)
[procedure] (rad->deg rad)
[procedure] (deg->rad deg)
[procedure] (hms->deg hms)
[procedure] (deg->hms deg)
[procedure] (get-date)
[procedure] (vsop87->fk5 helio jd)

Rise, Set, Transit

[procedure] (object-rst jd ecl-observer equ-object)
[procedure] (object-next-rst jd ecl-observer equ-object)
[procedure] (object-next-rst-horizon jd ecl-observer equ-object horizon)
[procedure] (body-rst-horizon jd ecl-observer body-object horizon)
[procedure] (body-next-rst-horizon jd ecl-observer body-object horizon)
[procedure] (body-next-rst-horizon-future jd ecl-observer body-object horizon day-limit)

Motion

Elliptic Motion

[procedure] (solve-kepler e M)
[procedure] (ell-mean-anomaly n delta-jd)
[procedure] (ell-true-anomaly e E)
[procedure] (ell-radius-vector a e E)
[procedure] (ell-smajor-diam e q)
[procedure] (ell-sminor-diam e a)
[procedure] (ell-mean-motion a)
[procedure] (ell-geo-rect-posn ell jd)
[procedure] (ell-helio-rect-posn ell jd)
[procedure] (ell-orbit-len ell)
[procedure] (ell-orbit-vel jd ell)
[procedure] (ell-orbit-pvel ell)
[procedure] (ell-orbit-avel ell)
[procedure] (ell-body-phase-angle jd ell)
[procedure] (ell-body-elong jd ell)
[procedure] (ell-body-solar-dist jd ell)
[procedure] (ell-body-earth-dist jd ell)
[procedure] (ell-body-equ-coords jd ell)
[procedure] (ell-body-rst jd ecl)
[procedure] (ell-body-rst-horizon jd ecl ell horizon)
[procedure] (ell-body-next-rst-horizon jd ecl ell horizon)
[procedure] (ell-body-next-rst-horizon-future jd ecl ell horizon day-limit)
[procedure] (ell-last-perihelion epoch-jd M n)

Hyperbolic Motion

[procedure] (solve-hyp-barker Q1 G t)
[procedure] (hyp-true-anomaly q e t)
[procedure] (hyp-radius-vector q e t)
[procedure] (hyp-geo-rect-posn h)
[procedure] (hyp-helio-rect-posn hyp jd)
[procedure] (hyp-body-equ-coords jd hyp)
[procedure] (hyp-body-earth-dist jd hyp)
[procedure] (hyp-body-solar-dist jd hyp)
[procedure] (hyp-body-phase-angle jd hyp)
[procedure] (hyp-body-elong jd hyp)
[procedure] (hyp-body-rst jd ecl hyp)
[procedure] (hyp-body-rst-horizon jd ecl hyp horizon)
[procedure] (hyp-body-next-rst-horizon jd ecl hyp horizon)
[procedure] (hyp-body-next-rst-horizon-future jd ecl hyp horizon day-limit)

Parabolic Motion

[procedure] (solve-barker q t)
[procedure] (par-true-anomaly q t)
[procedure] (par-radius-vector q t)
[procedure] (par-geo-rect-posn par jd)
[procedure] (par-helio-rect-posn par jd)
[procedure] (par-body-equ-coords jd par)
[procedure] (par-body-earth-dist jd par)
[procedure] (par-body-solar-dist jd par)
[procedure] (par-body-phase-angle jd par)
[procedure] (par-body-elong jd par)
[procedure] (par-body-rst jd ecl par)
[procedure] (par-body-rst-horizon jd ecl par horizon)
[procedure] (par-body-next-rst-horizon jd ecl par horizon)
[procedure] (par-body-next-rst-horizon-future jd ecl par horizon day-limit)

Bodies

Sun

[procedure] (solar-rst-horizon jd ecl horizon)
[procedure] (solar-rst jd ecl)
[procedure] (solar-geom-coords jd)
[procedure] (solar-equ-coords jd)
[procedure] (solar-ecl-coords jd)
[procedure] (solar-geo-coords jd)
[procedure] (solar-sdiam jd)

Earth

[procedure] (earth-helio-coords jd)
[procedure] (earth-solar-dist jd)
[procedure] (earth-rect-helio jd)
[procedure] (earth-centre-dist height latitude)

Moon

[procedure] (lunar-phase jd)
[procedure] (lunar-disk jd)
[procedure] (lunar-sdiam jd)
[procedure] (lunar-earth-dist jd)
[procedure] (lunar-bright-limb jd)
[procedure] (lunar-long-asc-node jd)
[procedure] (lunar-long-perigee jd)
[procedure] (lunar-equ-coords jd precision)
[procedure] (lunar-rst jd ecl)
[procedure] (lunar-geo-posn jd precision)
[procedure] (lunar-equ-coords-prec jd precision)
[procedure] (lunar-ecl-coords jd precision)

Mercury

[procedure] (mercury-sdiam jd)
[procedure] (mercury-rst jd ecl)
[procedure] (mercury-helio-coords jd)
[procedure] (mercury-equ-coords jd)
[procedure] (mercury-earth-dist jd)
[procedure] (mercury-solar-dist jd)
[procedure] (mercury-magnitude jd)
[procedure] (mercury-disk jd)
[procedure] (mercury-phase jd)
[procedure] (mercury-rect-helio jd)

Venus

[procedure] (venus-sdiam jd)
[procedure] (venus-rst jd ecl)
[procedure] (venus-helio-coords jd)
[procedure] (venus-equ-coords jd)
[procedure] (venus-earth-dist jd)
[procedure] (venus-solar-dist jd)
[procedure] (venus-magnitude jd)
[procedure] (venus-disk jd)
[procedure] (venus-phase jd)
[procedure] (venus-rect-helio jd)

Mars

[procedure] (mars-sdiam jd)
[procedure] (mars-rst jd ecl)
[procedure] (mars-helio-coords jd)
[procedure] (mars-equ-coords jd)
[procedure] (mars-earth-dist jd)
[procedure] (mars-solar-dist jd)
[procedure] (mars-magnitude jd)
[procedure] (mars-disk jd)
[procedure] (mars-phase jd)
[procedure] (mars-rect-helio jd)

Jupiter

[procedure] (jupiter-equ-sdiam jd)
[procedure] (jupiter-pol-sdiam jd)
[procedure] (jupiter-rst jd ecl)
[procedure] (jupiter-helio-coords jd)
[procedure] (jupiter-equ-coords jd)
[procedure] (jupiter-earth-dist jd)
[procedure] (jupiter-solar-dist jd)
[procedure] (jupiter-magnitude jd)
[procedure] (jupiter-disk jd)
[procedure] (jupiter-phase jd)
[procedure] (jupiter-rect-helio jd)

Saturn

[procedure] (saturn-equ-sdiam jd)
[procedure] (saturn-pol-sdiam jd)
[procedure] (saturn-rst jd ecl)
[procedure] (saturn-helio-coords jd)
[procedure] (saturn-equ-coords jd)
[procedure] (saturn-earth-dist jd)
[procedure] (saturn-solar-dist jd)
[procedure] (saturn-magnitude jd)
[procedure] (saturn-disk jd)
[procedure] (saturn-phase jd)
[procedure] (saturn-rect-helio jd)

Uranus

[procedure] (uranus-sdiam jd)
[procedure] (uranus-rst jd ecl)
[procedure] (uranus-helio-coords jd)
[procedure] (uranus-equ-coords jd)
[procedure] (uranus-earth-dist jd)
[procedure] (uranus-solar-dist jd)
[procedure] (uranus-magnitude jd)
[procedure] (uranus-disk jd)
[procedure] (uranus-phase jd)
[procedure] (uranus-rect-helio jd)

Neptune

[procedure] (neptune-sdiam jd)
[procedure] (neptune-rst jd ecl)
[procedure] (neptune-helio-coords jd)
[procedure] (neptune-equ-coords jd)
[procedure] (neptune-earth-dist jd)
[procedure] (neptune-solar-dist jd)
[procedure] (neptune-magnitude jd)
[procedure] (neptune-disk jd)
[procedure] (neptune-phase jd)
[procedure] (neptune-rect-helio jd)

Pluto

[procedure] (pluto-sdiam jd)
[procedure] (pluto-rst jd ecl)
[procedure] (pluto-helio-coords jd)
[procedure] (pluto-equ-coords jd)
[procedure] (pluto-earth-dist jd)
[procedure] (pluto-solar-dist jd)
[procedure] (pluto-magnitude jd)
[procedure] (pluto-disk jd)
[procedure] (pluto-phase jd)
[procedure] (pluto-rect-helio jd)

Misc

[procedure] (heliocentric-time-diff jd equ)
[procedure] (refraction-adj altitude atm-pressure temp)
[procedure] (equ-aberration equ jd)
[procedure] (ecl-aberration equ jd)
[procedure] (dynamical-time-diff jde)
[procedure] (jde jd)
[procedure] (angular-separation equ equ)
[procedure] (rel-posn-angle equ equ)
[procedure] (constellation)
[procedure] (apparent-posn equ-mean equ-proper jd)
[procedure] (nutation jd)
[procedure] (equ-prec equ-mean jd)
[procedure] (equ-prec2 equ-mean jd jd)
[procedure] (ecl-prec ecl jd)
[procedure] (ell-comet-mag jd ell g k)
[procedure] (par-comet-mag jd par g k)

Transforms

[procedure] (hrz-from-equ equ ecl jd)
[procedure] (hrz-from-equ-sidereal-time equ ecl sidereal)
[procedure] (equ-from-ecl ecl jd)
[procedure] (ecl-from-equ equ jd)
[procedure] (rect-from-helio helio)
[procedure] (ecl-from-rect rect)
[procedure] (equ-from-gal gal)
[procedure] (equ2000-from-gal gal)
[procedure] (gal-from-equ equ)
[procedure] (gal-from-equ2000 equ)

Non-Libnova

[procedure] (range-hours hours)
[procedure] (range-degrees degrees)
[procedure] (range-degrees180 degrees)
[procedure] (is-above-horizon? equ ecl jd)
[procedure] (dms->deg dms)
[procedure] (hms->hr hms)

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