Class: Astronoby::Aberration

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

Constant Summary collapse

MAXIMUM_SHIFT = 
Angle.from_degrees(20.5)

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(coordinates, epoch) ⇒ Aberration

Returns a new instance of Aberration.



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# File 'lib/astronoby/aberration.rb', line 11

def initialize(coordinates, epoch)
  @coordinates = coordinates
  @epoch = epoch
end

Class Method Details

.for_ecliptic_coordinates(coordinates:, epoch:) ⇒ Object 



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# File 'lib/astronoby/aberration.rb', line 7

def self.for_ecliptic_coordinates(coordinates:, epoch:)
  new(coordinates, epoch).apply
end

Instance Method Details

#apply ⇒ Object

Source:

Title: Practical Astronomy with your Calculator or Spreadsheet
Authors: Peter Duffett-Smith and Jonathan Zwart
Edition: Cambridge University Press
Chapter: 36 - Aberration



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# File 'lib/astronoby/aberration.rb', line 21

def apply
  delta_longitude = Angle.from_degrees(
    -MAXIMUM_SHIFT.degrees * (
      sun_longitude - @coordinates.longitude
    ).cos / @coordinates.latitude.cos / Constants::SECONDS_PER_DEGREE
  )

  delta_latitude = Angle.from_degrees(
    -MAXIMUM_SHIFT.degrees *
    (sun_longitude - @coordinates.longitude).sin *
    @coordinates.latitude.sin / Constants::SECONDS_PER_DEGREE
  )

  Coordinates::Ecliptic.new(
    latitude: @coordinates.latitude + delta_latitude,
    longitude: @coordinates.longitude + delta_longitude
  )
end

#sun_longitude ⇒ Object 



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# File 'lib/astronoby/aberration.rb', line 40

def sun_longitude
  @_sun_longitude ||= Sun
    .new(time: Epoch.to_utc(@epoch))
    .true_ecliptic_coordinates
    .longitude
end