Module: AstroChart::Points

Defined in:
lib/astro_chart/points.rb

Overview

Derived chart points that are not physical bodies: 福點 (Part of Fortune) and 莉莉絲 (mean Black Moon Lilith / mean lunar apogee).

Class Method Summary collapse

Class Method Details

.antiscion(longitude) ⇒ Object

Antiscion (映點): the reflection of an ecliptic longitude across the Cancer–Capricorn solstice axis (0° 巨蟹 / 0° 摩羯). Two points are in antiscia when they are equidistant from that axis and thus receive the same amount of daylight; classically read as a hidden conjunction.

antiscion = (180 − L) mod 360

e.g. 15° 牡羊 (L=15) → 15° 處女 (165); a point on the axis maps to itself.



52
53
54
 
# File 'lib/astro_chart/points.rb', line 52

def self.antiscion(longitude)
  (180.0 - longitude) % 360.0
end

.contra_antiscion(longitude) ⇒ Object

Contra-antiscion (反映點): reflection across the Aries–Libra equinox axis (0° 牡羊 / 0° 天秤) — the antiscion's opposite point.

contra_antiscion = (360 − L) mod 360


60
61
62
 
# File 'lib/astro_chart/points.rb', line 60

def self.contra_antiscion(longitude)
  (360.0 - longitude) % 360.0
end

.day_chart?(sun_longitude, cusps) ⇒ Boolean

Whether the chart is a day birth: the Sun is above the horizon, i.e. the Sun falls in houses 7-12 for the given house cusps. Returns nil when the Sun cannot be placed (nil/empty inputs).

Note: this matches the horizon only for quadrant systems whose cusp 1 is the ascendant (e.g. Placidus). For sect determination independent of the display house system, use .day_chart_from_horizon? instead.

Returns:

  • (Boolean) 


25
26
27
28
29
30
 
# File 'lib/astro_chart/points.rb', line 25

def self.day_chart?(sun_longitude, cusps)
  house = Houses.find_house(sun_longitude, cusps)
  return nil if house.nil?

  house >= 7
end

.day_chart_from_horizon?(sun_longitude, ascendant) ⇒ Boolean

Whether the chart is a day birth, judged directly from the horizon (ASC–DSC axis): the Sun is above the horizon when its ecliptic longitude lies in the half-circle from the descendant (ASC + 180°) forward to the ascendant — equivalent to quadrant houses 7-12. Sect is an astronomical fact, so this is independent of the display house system. Returns nil when either input is missing.

Returns:

  • (Boolean) 


38
39
40
41
42
 
# File 'lib/astro_chart/points.rb', line 38

def self.day_chart_from_horizon?(sun_longitude, ascendant)
  return nil if sun_longitude.nil? || ascendant.nil?

  ((sun_longitude - ascendant) % 360.0) >= 180.0
end

.fortune(asc:, sun:, moon:, day_chart:) ⇒ Object

Part of Fortune (福點), ecliptic longitude in degrees 0-360.

Day chart: ASC + Moon - Sun Night chart: ASC - Moon + Sun



13
14
15
16
 
# File 'lib/astro_chart/points.rb', line 13

def self.fortune(asc:, sun:, moon:, day_chart:)
  longitude = day_chart ? asc + moon - sun : asc - moon + sun
  longitude % 360.0
end

.lilith(jd) ⇒ Object

Mean Black Moon Lilith (莉莉絲): ecliptic longitude of the mean lunar apogee, degrees 0-360, for a given Julian Day (UT).

Uses the mean longitude of the lunar perigee polynomial (Meeus, "Astronomical Algorithms", mean elements of the lunar orbit) + 180°. T is measured in Julian centuries from J2000.0. The TT-UT difference is ignored: the apogee moves ~0.111°/day, so delta-T contributes well under 0.001° in 1900-2100.



72
73
74
75
76
77
78
79
80
 
# File 'lib/astro_chart/points.rb', line 72

def self.lilith(jd)
  t = (jd - 2451545.0) / 36525.0
  perigee = 83.3532465 +
            4069.0137287 * t -
            0.0103200 * t**2 -
            t**3 / 80_053.0 +
            t**4 / 18_999_000.0
  (perigee + 180.0) % 360.0
end