This is gcal.info, produced by makeinfo version 4.0 from gcal.texi.

INFO-DIR-SECTION GNU packages
START-INFO-DIR-ENTRY
* Gcal: (gcal).                       GNU calendar program.
* Tcal: (gcal)Invoking tcal.          Run Gcal with tomorrow's date.
* Txt2gcal: (gcal)Invoking txt2gcal.  Calendar text to resource file.
* Gcal2txt: (gcal)Invoking gcal2txt.  Calendar resource to text file.
END-INFO-DIR-ENTRY

  This file documents Gcal, a program for calculating and printing
calendars.

  Copyright (c) 1994-1997, 2000 Thomas Esken

  This edition is for Gcal version 3.00.

  Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

  Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

  Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that this permission notice may be stated in a
translation approved by the Free Software Foundation.

  Any suggestions, improvements, extensions, bug reports, donations,
proposals for contract work, and so forth are welcome!  Please send
them directly to my eMail address <esken@gmx.net>.  If you like my
work, I'd appreciate a postcard from you!

------------------------oOO      \\\_''/      OOo---------------------------
Thomas Esken               O     (/o-o\)     O  eMail: esken@gmx.net
Im Hagenfeld 84                 ((  ^  ))       Phone: +49 251 232585
D-48147 Muenster; Germany    \____) ~ (____/    MotD : 2old2live, 2young2die


File: gcal.info,  Node: Moon data,  Next: Contents of Environment variable,  Prev: Sun data,  Up: Replacements with other argument

Moon data `%[FORMAT]?ARGUMENT' special texts
............................................

  `%[FORMAT]([*][MODE]ISO-6709:1983-KOORDINATE[,[+|-]MMMM|HH:[MM]]'
references the approximate time of *moonrise* by default,
`%[FORMAT])[*][MODE]ISO-6709:1983-KOORDINATE[,[+|-]MMMM|HH:[MM]]'
references the approximate time of *moonset* by default,
`%[FORMAT][[*][MODE]ISO-6709:1983-KOORDINATE[,[+|-]MMMM|HH:[MM]]'
references the approximate period of *visibility* of the Moon (lunar
day length) by default,
`%[FORMAT]][*][MODE]ISO-6709:1983-KOORDINATE[,[+|-]MMMM|HH:[MM]]'
references the approximate period of *non-visibility* of the Moon
(lunar night length) by default.

  All these special texts can be used for at pleasure any geographic
point location, i.e. it is possible to determine different astronomical
values for any location on the globe, and that for at pleasure any
clocktime with a resolution of a single minute within the period of the
years AD 1 until AD 9999, that is respected by Gcal.

  The selection which value has to be calculated by these special texts
is done by specifying the MODE part of the preceding argument.
Actually, exactly 61 different modes can be used that are represented
by the `0'...`9', `a'...`z' and `A'...`Y' characters, and which create
different kind of results that are depending on the special text used.
First of all, here is a table in which all usable modes are described
and explained sufficiently.  You can also see from this table, which
Moon oriented special text or texts are corresponding to which mode,
i.e. cause the determination of an astronomical value as it is
described in the table:

*Mode*  *Special      *Description*
        text*         

`0'     `(', `)'      Calculates the approximate midnight time of the
                      Moon.  The astronomical midnight time of the Moon
                      is at that clocktime, when the Moon holds an
                      "azimuth" (horizontal angular distance between the
                      vertical circle, that passes the Moon, and the
                      North point) of either precisely 0 degrees of
                      precisely 180 degrees, which depends on the season
                      and the geographical location.  At that clocktime,
                      the Moon is close its "lowest culmination point",
                      i.e. close the lowest point below or above the
                      horizontal plane the Moon transits during this day.
                      Nevertheless, there is exactly one day during a
                      "synodic month" (or lunation) --i.e. the mean time
                      between two consecutive "conjunctions" (or New Moon
                      phases)-- at which no lunar midnight happens,
                      because the Moon revolves the Earth within 24 hours
                      and 50 minutes on the average -- which also means,
                      that the Moon rises on the average 50 minutes later
                      each day.

`1'     `(', `)'      Calculates the approximate noon time of the Moon.
                      The astronomical noon time of the Moon is at that
                      clocktime, when the Moon holds an azimuth of either
                      precisely 180 degrees of precisely 0 degrees, which
                      depends on the season and the geographical location.
                      At that clocktime, the Moon is close its "highest
                      culmination point", i.e. close the highest point
                      above or below the horizontal plane the Moon
                      transits during this day.  Nevertheless, there is
                      exactly one day during a synodic month at which no
                      lunar noon happens.

`2'     `('           Calculates the approximate time when the center of
                      the Moon passes a reference altitude which is
                      between about 54 and 61 arcminutes above a
                      "mathematical-geocentric" horizon before lunar noon
                      time; thus rising.  A mathematical horizion is a
                      purely geometrically-built horizon which disregards
                      the phenomenon of refraction as it arises in
                      reality by the influence of the Earth's atmosphere.
                      A geocentrical horizon is the horizontal plane
                      that passes through the Earth's center, orthogonal
                      to the observer's local vertical.  In the further
                      context, the shorter term _mathematical horizion_
                      is used which actually means the
                      mathematical-geocentric horizon.  The above
                      mentioned reference altitude is computed from the
                      value of the Moon's parallax as it appear at that
                      clocktime.  Nevertheless, there is exactly one day
                      during a synodic month at which no such moonrise
                      happens.

`2'     `)'           Calculates the approximate time when the center of
                      the Moon passes a reference altitude which is
                      between about 54 and 61 arcminutes above a
                      mathematical horizon after lunar noon time; thus
                      setting.  The above mentioned reference altitude is
                      computed from the value of the Moon's parallax as
                      it appear at that clocktime.  Nevertheless, there
                      is exactly one day during a synodic month at which
                      no such moonset happens.

`2'     `['           Calculates the approximate period while the center
                      of the Moon is above a reference altitude which is
                      between about 54 and 61 arcminutes above a
                      mathematical horizon; thus is visible.

`2'     `]'           Calculates the approximate period while the center
                      of the Moon is below a reference altitude which is
                      between about 54 and 61 arcminutes above a
                      mathematical horizon; thus is non-visible.

`3'     `('           Calculates the approximate time when the upper limb
                      of the Moon passes a reference altitude which is
                      between about 54 and 61 arcminutes above a
                      mathematical horizon before lunar noon time; thus
                      rising.  The above mentioned reference altitude is
                      computed from the respective values of the Moon's
                      semidiameter and Moon's parallax as they appear at
                      that clocktime.  If the reference altitude that is
                      refering to the Moon's upper limb is converted to a
                      reference altitude that is refering to the Moon's
                      center, this results in a value which is between
                      about 39 and 44 arcminutes above the geocentric
                      horizon.  Nevertheless, there is exactly one day
                      during a synodic month at which no such moonrise
                      happens.

`3'     `)'           Calculates the approximate time when the upper limb
                      of the Moon passes a reference altitude which is
                      between about 54 and 61 arcminutes above a
                      mathematical horizon after lunar noon time; thus
                      setting.  The above mentioned reference altitude is
                      computed from the respective values of the Moon's
                      semidiameter and Moon's parallax as they appear at
                      that clocktime.  Nevertheless, there is exactly one
                      day during a synodic month at which no such moonset
                      happens.

`3'     `['           Calculates the approximate period while the upper
                      limb of the Moon is above a reference altitude
                      which is between about 54 and 61 arcminutes above a
                      mathematical horizon; thus is visible.

`3'     `]'           Calculates the approximate period while the upper
                      limb of the Moon is below a reference altitude
                      which is between about 54 and 61 arcminutes above a
                      mathematical horizon; thus is non-visible.

`4'     `('           Calculates the approximate time when the center of
                      the Moon passes a reference altitude which is
                      between about 20 and 27 arcminutes above the
                      geocentric horizon before lunar noon time; thus
                      rising.  The phenomenon of refraction is already
                      respected in this as it arises in reality by the
                      influence of the Earth's atmosphere, and that with
                      the standard value of 34 arcminutes, which can
                      indirectly be changed by using the `--atmosphere'
                      option.  *Note Fixed dates option
                      `--atmosphere=AIR-PRESSURE[,TEMPERATURE]':
                      x-atmosphere, how to change the base data of the
                      atmosphere, so that the atmospheric conditions as
                      defined by it are used to calculate the amount of
                      refraction.  The above mentioned reference altitude
                      is computed from the respective values of the
                      Moon's parallax and (standard) refraction as they
                      appear at that clocktime.  Nevertheless, there is
                      exactly one day during a synodic month at which no
                      such moonrise happens.

`4'     `)'           Calculates the approximate time when the center of
                      the Moon passes a reference altitude which is
                      between about 20 and 27 arcminutes above the
                      geocentric horizon after lunar noon time; thus
                      setting.  The phenomenon of refraction is already
                      respected in this as it arises in reality by the
                      influence of the Earth's atmosphere, and that with
                      the standard value of 34 arcminutes, which can
                      indirectly be changed by using the `--atmosphere'
                      option.  The above mentioned reference altitude is
                      computed from the respective values of the Moon's
                      parallax and (standard) refraction as they appear
                      at that clocktime.  Nevertheless, there is exactly
                      one day during a synodic month at which no such
                      moonset happens.

`4'     `['           Calculates the approximate period while the center
                      of the Moon is above a reference altitude which is
                      between about 20 and 27 arcminutes above the
                      geocentric horizon; thus is visible.

`4'     `]'           Calculates the approximate period while the center
                      of the Moon is below a reference altitude which is
                      between about 20 and 27 arcminutes above the
                      geocentric horizon; thus is non-visible.

`5'     `('           Calculates the approximate time when the upper limb
                      of the Moon passes a reference altitude which is
                      between about 20 and 27 arcminutes above the
                      geocentric horizon before lunar noon time; thus
                      rising.  This kind of rise time calculation is done
                      according to the standard calculation method as it
                      is commonly used internationally.  The phenomenon
                      of refraction is already respected in this as it
                      arises in reality by the influence of the Earth's
                      atmosphere, and that with the standard value of 34
                      arcminutes, which can indirectly be changed by
                      using the `--atmosphere' option.  *Note Fixed dates
                      option `--atmosphere=AIR-PRESSURE[,TEMPERATURE]':
                      x-atmosphere, how to change the base data of the
                      atmosphere, so that the atmospheric conditions as
                      defined by it are used to calculate the amount of
                      refraction.  The above mentioned reference altitude
                      is computed from the respective values of the
                      Moon's semidiameter, Moon's parallax and (standard)
                      refraction as they appear at that clocktime.  If
                      the reference altitude that is refering to the
                      Moon's upper limb is converted to a reference
                      altitude that is refering to the Moon's center,
                      this results in a value which is between about 5
                      and 10 arcminutes above the geocentric horizon.
                      Nevertheless, there is exactly one day during a
                      synodic month at which no such moonrise happens.

`5'     `)'           Calculates the approximate time at which the upper
                      limb of the Moon passes a reference altitude which
                      is between about 20 and 27 arcminutes above the
                      geocentric horizon after lunar noon time; thus
                      setting.  This kind of set time calculation is done
                      according to the standard calculation method as it
                      is commonly used internationally.  The phenomenon
                      of refraction is alread respected in this as it
                      arises in reality by the influence of the Earth's
                      atmosphere, and that with the standard value of 34
                      arcminutes, which can indirectly be changed by
                      using the `--atmosphere' option.  The above
                      mentioned reference altitude is computed from the
                      respective values of the Moon's semidiameter,
                      Moon's parallax and (standard) refraction as they
                      appear at that clocktime.  Nevertheless, there is
                      exactly one day during a synodic month at which no
                      such moonset happens.

`5'     `['           Calculates the approximate period while the upper
                      limb of the Moon is above a reference altitude
                      which is between about 20 and 27 arcminutes above
                      the geocentric horizon; thus is visible.  This kind
                      of visibility period calculation is done according
                      to the standard calculation method as it is
                      commonly used internationally.

`5'     `]'           Calculates the approximate period while the upper
                      limb of the Moon is below a reference altitude
                      which is between about 20 and 27 arcminutes above
                      the geocentric horizon; thus is non-visible.  This
                      kind of non-visibility period calculation is done
                      according to the standard calculation method as it
                      is commonly used internationally.

`6'     `(', `)'      Calculates the approximate "topocentric", apparent
                      "horizontal parallax" of the Moon in degrees and
                      arcminutes as it happen at civil midnight time.
                      The Moon's parallax states the diameter of the
                      Earth as it is seen from the surface of the Moon.
                      Observations of celestial objects that are done
                      from the surface of the Earth yield in
                      topocentrically based data.  The locations of the
                      celestial bodys are oftenly at another place if the
                      data is topocentrially determined instead of
                      determing it "geocentrically", i.e. at the fictious
                      center of the Earth.  This is mainly caused by the
                      refraction, which raises a celestial body to
                      another location as it is been in reality.  Because
                      the terrestrial globe flattens towards the pole
                      caps and therefore cannot be taken as an ideally
                      shaped sphere, the individual Earth radius between
                      the observer's location and the center of the Earth
                      also affects the computation of topocentrically
                      based data.

`7'     `(', `)'      Calculates the approximate topocentric, apparent
                      semidiameter of the Moon in degrees and arcminutes
                      as it happen at civil midnight time.

`8'     `(', `)'      Calculates the approximate topocentric, apparent
                      brightness of the Moon in "magnitude units" as it
                      happen at civil midnight time.  The magnitude
                      (latin term `magnitudo', abbreviated m) is used to
                      define the brightness of a star, and is a
                      non-metrical value.  The difference between two
                      consecutive magnitudes is 1 to 2.512.  Therefore, a
                      star with the brightness of 1m is 2.512 times
                      brighter than a star of 2m.  A negative magitude
                      denotes a very bright star, for example almost -27m
                      for the Sun, whereas the hardly visible planet
                      Pluto has a magnitude of a bit more than +14m.  The
                      Full Moon has a visual brightness of about -12m.55.

`9'     `(', `)'      Calculates the approximate topocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at civil midnight time.

`a'     `(', `)'      Calculates the approximate topocentric, apparent
                      "elevation" of the Moon, thus the vertical angular
                      distance between the Moon's center and the horizon,
                      in degrees and arcminutes as it happen at civil
                      midnight time.  Results with a negative sign
                      signify that the Moon's center is below the horizon
                      at the moment, and results with a positive sign
                      mean that the momentary center of the Moon is above
                      the horizon.

`b'     `(', `)'      Calculates the approximate topocentric, apparent
                      azimuth of the Moon in degrees and arcminutes as it
                      happen at civil midnight time.

`c'     `(', `)'      Calculates the approximate topocentric, apparent
                      "declination" of the Moon, thus the vertical
                      angular distance between the Moon's center and the
                      celestial equator, in degrees and arcminutes as it
                      happen at civil midnight time.  Results with a
                      negative sign signify that the Moon's center is
                      below the celestial equator at the moment, and
                      results with a positive sign mean that the
                      momentary center of the Moon is above the celestial
                      equator.

`d'     `(', `)'      Calculates the approximate topocentric, apparent
                      "ecliptic longitude" of the Moon, thus the
                      horizontal angular distance between the Moon's
                      center and the vernal equinox point on the
                      "ecliptic" (the zodiacal line or Sun's orbit), in
                      degrees and arcminutes as it happen at civil
                      midnight time.

`e'     `(', `)'      Calculates the approximate topocentric, apparent
                      "ecliptic latitude" of the Moon, thus the vertical
                      angular distance between the Moon's center and the
                      ecliptic (zodiacal line/Sun's orbit), in degrees
                      and arcminutes as it happen at civil midnight time.
                      Results with a negative sign signify that the
                      Moon's center is North of the ecliptic at the
                      moment, and results with a positive sign mean that
                      the momentary center of the Moon is South of the
                      ecliptic.

`f'     `(', `)'      Calculates the approximate topocentric, apparent
                      "right ascension" of the Moon, thus the horizontal
                      angular distance between the Moon's center and the
                      hour circle that passes through the vernal equinox
                      point on the ecliptic, as time value in hours and
                      minutes as it happen at civil midnight time.

`g'     `(', `)'      Calculates the approximate topocentric, apparent
                      distance of the Moon from the Earth in mean "Earth
                      equator radii" as it happen at civil midnight time.
                      The mean radius of Earth at the equator is about
                      6,378.137 kilometer.

`h'     `(', `)'      Calculates the approximate topocentric, apparent
                      "elongation" of the Moon, thus the horizontal
                      angular distance between the Moon's center and the
                      Sun's center, in degrees and arcminutes as it
                      happen at civil midnight time.

`i'     `(', `)'      Calculates the approximate refraction of the
                      Earth's atmosphere in degrees and arcminutes as it
                      happen at civil midnight time.

`j'     `(', `)'      Calculates the approximate geocentric, apparent
                      horizontal parallax of the Moon in degrees and
                      arcminutes as it happen at civil midnight time.

`k'     `(', `)'      Calculates the approximate geocentric, apparent
                      semidiameter of the Moon in degrees and arcminutes
                      as it happen at civil midnight time.

`l'     `(', `)'      Calculates the approximate geocentric, apparent
                      brightness of the Moon in magnitude units as it
                      happen at civil midnight time.

`m'     `(', `)'      Calculates the approximate geocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at civil midnight time.

`n'     `(', `)'      Calculates the approximate geocentric, apparent
                      elevation of the Moon in degrees and arcminutes as
                      it happen at civil midnight time.  Results with a
                      negative sign signify that the Moon's center is
                      below the horizon at the moment, and results with a
                      positive sign mean that the momentary center of the
                      Moon is above the horizon.

`o'     `(', `)'      Calculates the approximate geocentric, apparent
                      azimuth of the Moon in degrees and arcminutes as it
                      happen at civil midnight time.

`p'     `(', `)'      Calculates the approximate geocentric, apparent
                      declination of the Moon in degrees and arcminutes
                      as it happen at civil midnight time.  Results with
                      a negative sign signify that the Moon's center is
                      below the celestial equator at the moment, and
                      results with a positive sign mean that the
                      momentary center of the Moon is above the celestial
                      equator.

`q'     `(', `)'      Calculates the approximate geocentric, apparent
                      ecliptic longitude of the Moon in degrees and
                      arcminutes as it happen at civil midnight time.

`r'     `(', `)'      Calculates the approximate geocentric, apparent
                      ecliptic latitude of the Moon in degrees and
                      arcminutes as it happen at civil midnight time.
                      Results with a negative sign signify that the
                      Moon's center is North of the ecliptic at the
                      moment, and results with a positive sign mean that
                      the momentary center of the Moon is South of the
                      ecliptic.

`s'     `(', `)'      Calculates the approximate geocentric, apparent
                      right ascension of the Moon as time value in hours
                      and minutes as it happen at civil midnight time.

`t'     `(', `)'      Calculates the approximate geocentric, apparent
                      distance of the Moon from the Earth in mean Earth
                      equator radii as it happen at civil midnight time.

`u'     `(', `)'      Calculates the approximate geocentric, apparent
                      elongation of the Moon in degrees and arcminutes as
                      it happen at civil midnight time.

`v'     `(', `)'      Calculates the approximate "delta-t" in seconds as
                      it happen at civil midnight time.  Delta-t is the
                      difference between the Terrestrial Dynamical time
                      (abbreviated by TDT), that was formerly known as
                      _Ephemeris time_ (abbreviated by ET), and the
                      Universal time (UT).  Thus, `delta-t == TDT - UT'.

`w'     `(', `)'      Calculates the approximate, apparent location
                      oriented "sidereal time" (local sidereal time
                      (LAST), also known as _local star time_) in hours
                      and minutes as it happen at civil midnight time.  A
                      "star day" is the period between two consecutive
                      upper culminations of the vernal equinox point on
                      the ecliptic in the meridian of the observer's
                      location.  Therefore, the local "star time" is the
                      momentary period, which is past between the last
                      upper culmination of the vernal equinox point in
                      the meridian of the observer's location (the
                      momentary hour angle of the vernal equinox point),
                      thus the right ascension of the stars in the
                      observer's meridian at the moment.

`x'     `(', `)'      Outputs the base time as time value in hours and
                      minutes, for which the dynamical, i.e. depending on
                      the respective clocktime, astronomical data and
                      times of the Moon are calculated.  Without a given
                      `--time-offset=ARGUMENT' option, the astronomical
                      data and times of the Moon are always calculated
                      for 0 o'clock Universal time (UTC/GMT).  *Note
                      Calendar option `--time-offset=ARGUMENT':
                      x-time-offset, for further details.

`y'     `(', `)'      Calculates the approximate Julian date in days as
                      it happen at civil midnight time.  *Note Julian day
                      number::, for further information about the Julian
                      date.

`z'     `(', `)'      Calculates the approximate "Julian Ephemeris date",
                      thus a Julian date that is corrected by _delta-t_,
                      in days as it happen at civil midnight time.

`A'     `(', `)'      Calculates the difference of the approximate
                      topocentric, apparent elevation of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      civil midnight time.  Results with a negative sign
                      signify that the momentary center of the Moon is at
                      an elevation that is below the momentary elevation
                      of the Sun's center; thus the Moon is lower than
                      the Sun.  Results with a positive sign signify that
                      the momentary center of the Moon is at an elevation
                      that is above the momentary elevation of the Sun's
                      center; thus the Moon is higher than the Sun.

`B'     `(', `)'      Calculates the difference of the approximate
                      topocentric, apparent azimuth of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      civil midnight time.  The result specifies the
                      horizontal angular distance, by which the momentary
                      center of the Moon is distant from the momentary
                      Sun's center, and that measured at the vertical
                      circles that pass the Moon and the North point and
                      the Sun and the North point.  Results with a
                      negative sign signify that the Sun is to the right
                      (clockwise) of the Moon if one looks to the Moon --
                      or alternatively expressed, that the Moon is to the
                      left (anti-clockwise) of the Sun.  Results with a
                      positive sign signify that the Sun is to the left
                      (anti-clockwise) of the Moon if one looks to the
                      Moon -- or alternatively expressed, that the Moon
                      is to the right (clockwise) of the Sun.

`C'     `(', `)'      Calculates the difference of the approximate
                      geocentric, apparent elevation of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      civil midnight time.

`D'     `(', `)'      Calculates the difference of the approximate
                      geocentric, apparent azimuth of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      civil midnight time.

`E'     `('           Calculates the difference of the approximate
                      topocentric, apparent elevation of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      standard rise time of the Moon.  *Note Standard
                      rise time of the Moon: x-Moon-standard-rise, for
                      further details.

`E'     `)'           Calculates the difference of the approximate
                      topocentric, apparent elevation of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      standard set time of the Moon.  *Note Standard set
                      time of the Moon: x-Moon-standard-set, for further
                      details.

`F'     `('           Calculates the difference of the approximate
                      topocentric, apparent azimuth of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      standard rise time of the Moon.  *Note Standard
                      rise time of the Moon: x-Moon-standard-rise, for
                      further details.

`F'     `)'           Calculates the difference of the approximate
                      topocentric, apparent azimuth of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      standard set time of the Moon.  *Note Standard set
                      time of the Moon: x-Moon-standard-set, for further
                      details.

`G'     `('           Calculates the difference of the approximate
                      geocentric, apparent elevation of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      standard rise time of the Moon.  *Note Standard
                      rise time of the Moon: x-Moon-standard-rise, for
                      further details.

`G'     `)'           Calculates the difference of the approximate
                      geocentric, apparent elevation of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      standard set time of the Moon.  *Note Standard set
                      time of the Moon: x-Moon-standard-set, for further
                      details.

`H'     `('           Calculates the difference of the approximate
                      geocentric, apparent azimuth of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      standard rise time of the Moon.  *Note Standard
                      rise time of the Moon: x-Moon-standard-rise, for
                      further details.

`H'     `)'           Calculates the difference of the approximate
                      geocentric, apparent azimuth of Moon and Sun
                      (delta), at which the Moon is used as the reference
                      point, in degrees and arcminutes as it happen at
                      standard set time of the Moon.  *Note Standard set
                      time of the Moon: x-Moon-standard-set, for further
                      details.

`I'     `(', `)'      Calculates the difference of the approximate
                      astronomical midnight times of Moon and Sun (delta),
                      at which the Moon is used as the reference point,
                      as time value in hours and minutes as it happen at
                      astronomical midnight time of the Moon.  Results
                      with a negative sign signify that the astronomical
                      midnight time of the Moon is earlier than the
                      astronomical midnight time of the Sun; thus the
                      lunar midnight is before the solar midnight.
                      Results with a positive sign signify that the
                      astronomical midnight time of the Moon is later
                      than the astronomical midnight time of the Sun;
                      thus the lunar midnight is after the solar midnight.
                      *Note Astronomical midnight time of the Moon:
                      x-Moon-midnight, and *Note Astronomical midnight
                      time of the Sun: x-Sun-midnight, for further
                      details.

`J'     `(', `)'      Calculates the difference of the approximate
                      astronomical noon times of Moon and Sun (delta), at
                      which the Moon is used as the reference point, as
                      time value in hours and minutes as it happen at
                      astronomical noon time of the Moon.  Results with a
                      negative sign signify that the astronomical noon
                      time of the Moon is earlier than the astronomical
                      noon time of the Sun; thus the lunar noon is before
                      the solar noon.  Results with a positive sign
                      signify that the astronomical noon time of the Moon
                      is later than the astronomical noon time of the Sun;
                      thus the lunar noon is after the solar noon.  *Note
                      Astronomical noon time of the Moon: x-Moon-noon, and
                      *Note Astronomical noon time of the Sun: x-Sun-noon,
                      for further details.

`K'     `('           Calculates the difference of the approximate
                      standard rise times of Moon and Sun (delta), at
                      which the Moon is used as the reference point, as
                      time value in hours and minutes as it happen at
                      standard rise time of the Moon.  Results with a
                      negative sign signify that the standard rise time
                      of the Moon is earlier than the standard rise time
                      of the Sun; thus the moonrise is before the sunrise.
                      Results with a positive sign signify that the
                      standard rise time of the Moon is later than the
                      standard rise time of the Sun; thus the moonrise is
                      after the sunrise.  *Note Standard rise time of the
                      Moon: x-Moon-standard-rise, and *Note Standard rise
                      time of the Sun: x-Sun-standard-rise, for further
                      details.

`K'     `)'           Calculates the difference of the approximate
                      standard set times of Moon and Sun (delta), at
                      which the Moon is used as the reference point, as
                      time value in hours and minutes as it happen at
                      standard set time of the Moon.  Results with a
                      negative sign signify that the standard set time of
                      the Moon is earlier than the standard set time of
                      the Sun; thus the moonset is before the sunset.
                      Results with a positive sign signify that the
                      standard set time of the Moon is later than the
                      standard set time of the Sun; thus the moonset is
                      after the sunset.  *Note Standard set time of the
                      Moon: x-Moon-standard-set, and *Note Standard set
                      time of the Sun: x-Sun-standard-set, for further
                      details.

`L'     `(', `)'      Calculates the approximate topocentric, apparent
                      elevation of the Moon in degrees and arcminutes as
                      it happen at astronomical midnight time of the Moon
                      (topocentric "midnight height").  *Note
                      Astronomical midnight time of the Moon:
                      x-Moon-midnight, for further details.

`M'     `(', `)'      Calculates the approximate topocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at astronomical midnight time of the Moon
                      (topocentric "midnight phase angle").  *Note
                      Astronomical midnight time of the Moon:
                      x-Moon-midnight, for further details.

`N'     `(', `)'      Calculates the approximate topocentric, apparent
                      elevation of the Moon in degrees and arcminutes as
                      it happen at astronomical noon time of the Moon
                      (topocentric "noon height").  *Note Astronomical
                      noon time of the Moon: x-Moon-noon, for further
                      details.

`O'     `(', `)'      Calculates the approximate topocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at astronomical noon time of the Moon
                      (topocentric "noon phase angle").  *Note
                      Astronomical noon time of the Moon: x-Moon-noon,
                      for further details.

`P'     `('           Calculates the approximate topocentric, apparent
                      elevation of the Moon in degrees and arcminutes as
                      it happen at standard rise time of the Moon
                      (topocentric "rise height").  *Note Standard rise
                      time of the Moon: x-Moon-standard-rise, for further
                      details.

`P'     `)'           Calculates the approximate topocentric, apparent
                      elevation of the Moon in degrees and arcminutes as
                      it happen at standard set time of the Moon
                      (topocentric "set height").  *Note Standard set
                      time of the Moon: x-Moon-standard-set, for further
                      details.

`Q'     `('           Calculates the approximate topocentric, apparent
                      azimuth of the Moon in degrees and arcminutes as it
                      happen at standard rise time of the Moon
                      (topocentric "rise azimuth").  The horizontal
                      angular distance between the topocentric rise
                      azimuth und the East direction is also known as the
                      topocentric "rise width" of the Moon.  *Note
                      Standard rise time of the Moon:
                      x-Moon-standard-rise, for further details.

`Q'     `)'           Calculates the approximate topocentric, apparent
                      azimuth of the Moon in degrees and arcminutes as it
                      happen at standard set time of the Moon
                      (topocentric "set azimuth").  The horizontal
                      angular distance between the topocentric set
                      azimuth und the West direction is also known as the
                      topocentric "set width" of the Moon.  *Note
                      Standard set time of the Moon: x-Moon-standard-set,
                      for further details.

`R'     `('           Calculates the approximate topocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at standard rise time of the Moon
                      (topocentric "rise phase angle").  *Note Standard
                      rise time of the Moon: x-Moon-standard-rise, for
                      further details.

`R'     `)'           Calculates the approximate topocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at standard set time of the Moon
                      (topocentric "set phase angle").  *Note Standard
                      set time of the Moon: x-Moon-standard-set, for
                      further details.

`S'     `(', `)'      Calculates the approximate geocentric, apparent
                      elevation of the Moon in degrees and arcminutes as
                      it happen at astronomical midnight time of the Moon
                      (geocentric "midnight height").  *Note Astronomical
                      midnight time of the Moon: x-Moon-midnight, for
                      further details.

`T'     `(', `)'      Calculates the approximate geocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at astronomical midnight time of the Moon
                      (geocentric "midnight phase angle").  *Note
                      Astronomical midnight time of the Moon:
                      x-Moon-midnight, for further details.

`U'     `(', `)'      Calculates the approximate geocentric, apparent
                      elevation of the Moon in degrees and arcminutes as
                      it happen at astronomical noon time of the Moon
                      (geocentric "noon height").  *Note Astronomical
                      noon time of the Moon: x-Moon-noon, for further
                      details.

`V'     `(', `)'      Calculates the approximate geocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at astronomical noon time of the Moon
                      (geocentric "noon phase angle").  *Note
                      Astronomical noon time of the Moon: x-Moon-noon,
                      for further details.

`W'     `('           Calculates the approximate geocentric, apparent
                      elevation of the Moon in degrees and arcminutes as
                      it happen at standard rise time of the Moon
                      (geocentric "rise height").  *Note Standard rise
                      time of the Moon: x-Moon-standard-rise, for further
                      details.

`W'     `)'           Calculates the approximate geocentric, apparent
                      elevation of the Moon in degrees and arcminutes as
                      it happen at standard set time of the Moon
                      (geocentric "set height").  *Note Standard set time
                      of the Moon: x-Moon-standard-set, for further
                      details.

`X'     `('           Calculates the approximate geocentric, apparent
                      azimuth of the Moon in degrees and arcminutes as it
                      happen at standard rise time of the Moon
                      (geocentric "rise azimuth").  The horizontal
                      angular distance between the geocentric rise
                      azimuth und the East direction is also known as the
                      geocentric "rise width" of the Moon.  *Note
                      Standard rise time of the Moon:
                      x-Moon-standard-rise, for further details.

`X'     `)'           Calculates the approximate geocentric, apparent
                      azimuth of the Moon in degrees and arcminutes as it
                      happen at standard set time of the Moon (geocentric
                      "set azimuth").  The horizontal angular distance
                      between the geocentric set azimuth und the West
                      direction is also known as the geocentric "set
                      width" of the Moon.  *Note Standard set time of the
                      Moon: x-Moon-standard-set, for further details.

`Y'     `('           Calculates the approximate geocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at standard rise time of the Moon
                      (geocentric "rise phase angle").  *Note Standard
                      rise time of the Moon: x-Moon-standard-rise, for
                      further details.

`Y'     `)'           Calculates the approximate geocentric, apparent
                      phase angle of the Moon in range 0.0...1.0 as it
                      happen at standard set time of the Moon (geocentric
                      "set phase angle").  *Note Standard set time of the
                      Moon: x-Moon-standard-set, for further details.

  If no MODE is given, Gcal automatically uses that mode, which is
enabled by the mode character `5'.  If a mode character is given that
is not according to one of the `0'...`9', `a'...`z' and `A'...`Y'
characters, Gcal also automatically uses that mode, which is enabled by
the mode character `5'.

  Depending on the selected mode, Gcal represents the Moon oriented
special texts using the same types and styles as they are used by the
Sun oriented special texts, these are analogously valid!  *Note
Representation of the Sun oriented special texts: x-Sun-representation,
for the detailed description of the different types of representation
used by the Sun oriented special texts, which are likewise valid for
the Moon oriented special texts.

  The ARGUMENT the Moon oriented special texts must have is exactly
equivalent the argument the Sun oriented special texts must have!
*Note Arguments of the Sun oriented special texts: x-Sun-arguments, for
the detailed description of the components of the ARGUMENT which also
has to be given to the Moon oriented special texts.

  The following table informs you about which type of representation is
caused by a mode.  The previously defined numbering scheme, as it has
been used for the introduction of the types of representation, is used
as key value in the column that holds the type of representation.  The
table also contains a column that shows whether a mode enables
dynamical values, i.e. values that are depending on the respective
clocktime (if you use the `--time-offset=ARGUMENT' option, you can
change the respective clocktime that is used for calculating such
values).  In a next table column, it is listed whether the given
co-ordinate of the location influences the determination of a value,
and the last column of the table gives you the information whether a
given timezone value affects the value's determination:

*Mode*  *Representation Type*  *Dynamical*    *Co-ordinate*  *Timezone*

`0'     3                      No             Yes            Yes
`1'     3                      No             Yes            Yes
`2'     3 or 4                 No             Yes            Yes
`3'     3 or 4                 No             Yes            Yes
`4'     3 or 4                 No             Yes            Yes
`5'     3 or 4                 No             Yes            Yes
`6'     6                      Yes            Yes            Yes
`7'     6                      Yes            Yes            Yes
`8'     2                      Yes            Yes            Yes
`9'     1 or 1b                Yes            Yes            Yes
`a'     7                      Yes            Yes            Yes
`b'     6                      Yes            Yes            Yes
`c'     7                      Yes            Yes            Yes
`d'     6                      Yes            Yes            Yes
`e'     7                      Yes            Yes            Yes
`f'     4                      Yes            Yes            Yes
`g'     1 or 1a                Yes            Yes            Yes
`h'     6                      Yes            Yes            Yes
`i'     6                      Yes            No             No
`j'     6                      Yes            Yes            Yes
`k'     6                      Yes            Yes            Yes
`l'     2                      Yes            Yes            Yes
`m'     1 or 1b                Yes            Yes            Yes
`n'     7                      Yes            Yes            Yes
`o'     6                      Yes            Yes            Yes
`p'     7                      Yes            Yes            Yes
`q'     6                      Yes            Yes            Yes
`r'     7                      Yes            Yes            Yes
`s'     4                      Yes            Yes            Yes
`t'     1 or 1a                Yes            Yes            Yes
`u'     6                      Yes            Yes            Yes
`v'     2                      Yes            No             No
`w'     3                      Yes            Yes            Yes
`x'     3                      Yes            No             No
`y'     1                      Yes            No             No
`z'     1                      Yes            No             No
`A'     7                      Yes            Yes            Yes
`B'     7                      Yes            Yes            Yes
`C'     7                      Yes            Yes            Yes
`D'     7                      Yes            Yes            Yes
`E'     7                      No             Yes            Yes
`F'     7                      No             Yes            Yes
`G'     7                      No             Yes            Yes
`H'     7                      No             Yes            Yes
`I'     5                      No             Yes            Yes
`J'     5                      No             Yes            Yes
`K'     5                      No             Yes            Yes
`L'     7                      No             Yes            Yes
`M'     1 or 1b                No             Yes            Yes
`N'     7                      No             Yes            Yes
`O'     1 or 1b                No             Yes            Yes
`P'     7                      No             Yes            Yes
`Q'     6                      No             Yes            Yes
`R'     1 or 1b                No             Yes            Yes
`S'     7                      No             Yes            Yes
`T'     1 or 1b                No             Yes            Yes
`U'     7                      No             Yes            Yes
`V'     1 or 1b                No             Yes            Yes
`W'     7                      No             Yes            Yes
`X'     6                      No             Yes            Yes
`Y'     1 or 1b                No             Yes            Yes

And now some examples to these special texts:

     The text `Moonrise at %(+5158+00738,120  in MS, BRD' will be
     expanded to
     ==> `Moonrise at 12:21 in MS, BRD', in case the actual system date
     is the 1st June 1998.

     The text `Moonset at %)*5+5158+00738,120  in MS, BRD' will be
     expanded to
     ==> `Moonset at 01:53am in MS, BRD', in case the actual system
     date is the 1st June 1998.

     The text `Moon visible %[5+5158+00738,120  in MS, BRD' will be
     expanded to
     ==> `Moon visible 13h32' in MS, BRD', in case the actual system
     date is the 1st June 1998.

     The text `Moon non-visible %]*+5158+00738,120  in MS, BRD' will be
     expanded to
     ==> `Moon non-visible 10.469 in MS, BRD', in case the actual
     system date is the 1st June 1998.

     The text `Moon azimuth 0 o'clock=%(*a+5158+00738,120  in MS, BRD'
     will be expanded to
     ==> `Moon azimuth 0 o'clock=267d37' in MS, BRD', in case the
     actual system date is the 1st June 1998.

     The text `Moonphase %(x+00+000 =%(*m+5158+00738,120 % in MS, BRD'
     will be expanded to
     ==> `Moonphase +16h00'=45.248% in MS, BRD', in case you call Gcal
     with the `--time-offset=16:' option and the actual system date is
     the 1st June 1998.

     The text `Julian date at %(x+00+000 =%(y+00+000' will be expanded
     to
     ==> `Julian date at +10h15'=2450965.927', in case you call Gcal
     with the `--time-offset=10:15' option and the actual system date
     is the 1st June 1998.

  Here is a list that reports about the used reference systems in a
short manner, describes other aspects that are unmentioned now, and
informs about the lacks and limitations that are existing for the Moon
oriented special texts:

   * All astronomical calculations are based on methods that use
     --astronomically seen-- low-precision elements, which of course is
     shown in the precision of the results that are caused by them.
     Nevertheless in most cases, these results can be treated as more
     as sufficiently precise if one measures their practical use.

   * All azimuth and elevation values are always refering to the center
     of the respective astronomical object, except the case, it is
     stated otherwise.

   * The base point of azimuth values, right ascension values and other
     ecliptic co-ordinate values is always measured clockwise relative
     to the geographical, true North (not the magnetic North as shown
     by a compass), where angular values for the North direction are
     both denoted as 0 degree and 360 degree.

   * All topocentrically based azimuth and elevation values are always
     corrected by the amount of atmospheric refraction.  Such a kind of
     correction is always done if the center of the respective
     astronomical object is above 2 degrees below the horizon.

   * Generally, the rise and set times of the Moon cannot be precisely
     predicted, because depending on unpredictable atmospheric
     conditions, i.e. the local weather conditions as they appear
     during these times change the amount of atmospheric refraction at
     the horizon, so that the precalculated rise and set times may
     throughout be in error by a minute or more.

   * The accurancy of rise and set computations decreases again at high
     latitudes, i.e. within in the lunar Arctic Circle.  There, small
     variations in atmospheric refraction can change the time of
     moonrise or moonset by many minutes, since the Moon intersects the
     horizon at a very shallow angle.  For the same reason, at high
     latitudes, the effects of observer height and local topography are
     magnified and can substantially change the times of the phenomena
     actually observed, or even whether the phenomena are observed to
     occur at all.

   * It is possible that calculations, which are done for locations
     within the lunar Arctic Circle, sometimes result in the wrongly
     **.** text instead of the more precisely ++:++ or -:- texts that
     are used for marking special events.  Unfortunately, therefore,
     then the reason why the Moon does not rise or set is no longer
     clearly evident, respectively, it is possible to get the false
     suggestion that the reason for non-rising or non-setting of the
     Moon is caused by just the one day within a synodic month, at which
     the Moon does not rise or set anyhow.  Unfortunately, it is just
     only obvious *that* the Moon does not rise or set during this day.

*Please also note the following references:*

   * *Note Fixed dates option `--precise': x-precise, how to obtain a
     more precise representation of the values which are cause by these
     special texts.

   * And note *Note Calendar option `--time-offset=ARGUMENT':
     x-time-offset, how to change the clocktime, for which the
     dynamical, i.e. depending on the respective clocktime, Moon
     oriented special texts are calculated.

   * Likewise, see *Note Fixed dates option `--cycle-end=ARGUMENT':
     x-cycle-end, how the dynamical, i.e. depending on the respective
     clocktime, Moon oriented special texts are calculated for a series
     of clocktimes for the current day.

   * Furthermode, see *Note Fixed dates option
     `--adjust-value=ARGUMENT': x-adjust-value, how to change the
     reference altitude that is used to calculate the rise and set
     times.

   * And last, note *Note Fixed dates option
     `--atmosphere=AIR-PRESSURE[,TEMPERATURE]': x-atmosphere, how to
     change the base data of the atmosphere that affects the calculation
     of the Moon oriented special texts.

  All Moon oriented special texts *must* always be trailed by a
_whitespace_ character which is removed in output!

