Class: Astronoby::TwilightCalculator

Inherits:
Object
  • Object
show all
Defined in:
lib/astronoby/events/twilight_calculator.rb

Constant Summary collapse

TWILIGHTS = 
[
  CIVIL = :civil,
  NAUTICAL = :nautical,
  ASTRONOMICAL = :astronomical
].freeze
TWILIGHT_ANGLES = 
{
  CIVIL => Angle.from_degrees(96),
  NAUTICAL => Angle.from_degrees(102),
  ASTRONOMICAL => Angle.from_degrees(108)
}.freeze
PERIODS_OF_THE_DAY = 
[
  MORNING = :morning,
  EVENING = :evening
].freeze

Instance Method Summary collapse

Constructor Details

#initialize(observer:, ephem:) ⇒ TwilightCalculator

Returns a new instance of TwilightCalculator.



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# File 'lib/astronoby/events/twilight_calculator.rb', line 22

def initialize(observer:, ephem:)
  @observer = observer
  @ephem = ephem
end

Instance Method Details

#event_on(date, utc_offset: 0) ⇒ Object 



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# File 'lib/astronoby/events/twilight_calculator.rb', line 27

def event_on(date, utc_offset: 0)
  start_time = Time
    .new(date.year, date.month, date.day, 0, 0, 0, utc_offset)
  end_time = Time
    .new(date.year, date.month, date.day, 23, 59, 59, utc_offset)
  events = events_between(start_time, end_time)

  TwilightEvent.new(
    morning_civil_twilight_time:
      events.morning_civil_twilight_times.first,
    evening_civil_twilight_time:
      events.evening_civil_twilight_times.first,
    morning_nautical_twilight_time:
      events.morning_nautical_twilight_times.first,
    evening_nautical_twilight_time:
      events.evening_nautical_twilight_times.first,
    morning_astronomical_twilight_time:
      events.morning_astronomical_twilight_times.first,
    evening_astronomical_twilight_time:
      events.evening_astronomical_twilight_times.first
  )
end

#events_between(start_time, end_time) ⇒ Object 



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# File 'lib/astronoby/events/twilight_calculator.rb', line 50

def events_between(start_time, end_time)
  rts_events = Astronoby::RiseTransitSetCalculator.new(
    body: Sun,
    observer: @observer,
    ephem: @ephem
  ).events_between(start_time, end_time)

  equatorial_by_time = {}

  (rts_events.rising_times + rts_events.setting_times)
    .compact
    .each do |event_time|
      rounded_time = event_time.round
      next if equatorial_by_time.key?(rounded_time)

      instant = Instant.from_time(rounded_time)
      sun_at_time = Sun.new(instant: instant, ephem: @ephem)
      equatorial_by_time[rounded_time] = sun_at_time.apparent.equatorial
    end

  morning_civil = []
  evening_civil = []
  morning_nautical = []
  evening_nautical = []
  morning_astronomical = []
  evening_astronomical = []

  arrays_by_period = {
    MORNING => {
      CIVIL => morning_civil,
      NAUTICAL => morning_nautical,
      ASTRONOMICAL => morning_astronomical
    },
    EVENING => {
      CIVIL => evening_civil,
      NAUTICAL => evening_nautical,
      ASTRONOMICAL => evening_astronomical
    }
  }

  [
    [rts_events.rising_times, MORNING],
    [rts_events.setting_times, EVENING]
  ].each do |times, period|
    times.each do |event_time|
      next unless event_time

      equatorial_coordinates = equatorial_by_time[event_time.round]
      TWILIGHT_ANGLES.each do |twilight, angle|
        arrays_by_period[period][twilight] << compute_twilight_time_from(
          period,
          angle,
          event_time,
          equatorial_coordinates
        )
      end
    end
  end

  within_range = ->(time) { time && time >= start_time && time <= end_time }

  TwilightEvents.new(
    morning_civil.select(&within_range),
    evening_civil.select(&within_range),
    morning_nautical.select(&within_range),
    evening_nautical.select(&within_range),
    morning_astronomical.select(&within_range),
    evening_astronomical.select(&within_range)
  )
end

#time_for_zenith_angle(date:, period_of_the_day:, zenith_angle:, utc_offset: 0) ⇒ Object 



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# File 'lib/astronoby/events/twilight_calculator.rb', line 121

def time_for_zenith_angle(
  date:,
  period_of_the_day:,
  zenith_angle:,
  utc_offset: 0
)
  unless PERIODS_OF_THE_DAY.include?(period_of_the_day)
    raise IncompatibleArgumentsError,
      "Only #{PERIODS_OF_THE_DAY.join(" or ")} are allowed as " \
      "period_of_the_day, got #{period_of_the_day}"
  end

  observation_events = get_observation_events(date, utc_offset: utc_offset)
  midday_instant = create_midday_instant(date, utc_offset: utc_offset)
  sun_at_midday = Sun.new(instant: midday_instant, ephem: @ephem)
  equatorial_coordinates = sun_at_midday.apparent.equatorial

  compute_twilight_time(
    period_of_the_day,
    zenith_angle,
    observation_events,
    equatorial_coordinates
  )
end