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| -rw-r--r-- | doc/info/solar-python.texinfo | 380 |
1 files changed, 159 insertions, 221 deletions
diff --git a/doc/info/solar-python.texinfo b/doc/info/solar-python.texinfo index b47a789..624e244 100644 --- a/doc/info/solar-python.texinfo +++ b/doc/info/solar-python.texinfo @@ -87,27 +87,35 @@ constants available: @table @code @item SOLAR_APPARENT_RADIUS = 32 / 60 Approximate apparent size of the Sun in degrees. + @item SOLAR_ELEVATION_SUNSET_SUNRISE = 0.0 The Sun's elevation at sunset and sunrise, measured in degrees. + @item SOLAR_ELEVATION_CIVIL_DUSK_DAWN = -6.0 The Sun's elevation at civil dusk and civil dawn, measured in degrees + @item SOLAR_ELEVATION_NAUTICAL_DUSK_DAWN = -12.0 The Sun's elevation at nautical dusk and nautical dawn, measured in degrees + @item SOLAR_ELEVATION_ASTRONOMICAL_DUSK_DAWN = -18.0 The Sun's elevation at astronomical dusk and astronomical dawn, measured in degrees + @item SOLAR_ELEVATION_RANGE_TWILIGHT = (-18.0, 0.0) The Sun's lowest and highest elevation during all periods of twilight, measured in degrees + @item SOLAR_ELEVATION_RANGE_CIVIL_TWILIGHT = (-6.0, 0.0) The Sun's lowest and highest elevation during civil twilight, measured in degrees + @item SOLAR_ELEVATION_RANGE_NAUTICAL_TWILIGHT = (-12.0, -6.0) The Sun's lowest and highest elevation during nautical twilight, measured in degrees + @item SOLAR_ELEVATION_RANGE_ASTRONOMICAL_TWILIGHT = (-18.0, -12.0) The Sun's lowest and highest elevation during astronomical twilight, measured in degrees @@ -121,19 +129,25 @@ astronomical twilight, measured in degrees Importing @code{solar_python} makes the following calendar conversion functions available. All parameters are of the type @code{float}, and -all functions return @code{float}. +all functions return @code{float} except where +noted otherwise. @table @code @item julian_day_to_epoch(t) Converts a Julian Day timestamp, @code{t}, to a POSIX time timestamp. + @item epoch_to_julian_day(t) Converts a POSIX time timestamp, @code{t}, to a Julian Day timestamp + @item julian_day_to_julian_centuries(t) Converts a Julian Day timestamp, @code{t}, to a Julian Centuries timestamp. + @item julian_centuries_to_julian_day(t) Converts a Julian Centuries timestamp, @code{t}, to a Julian Day timestamp. + @item epoch_to_julian_centuries(t) Converts a POSIX time timestamp, @code{t}, to a Julian Centuries timestamp. + @item julian_centuries_to_epoch(t) Converts a Julian Centuries timestamp, @code{t}, to a POSIX time timestamp. @end table @@ -146,8 +160,10 @@ type @code{float}, and all functions return @table @code @item epoch() Get current POSIX time. + @item julian_day() Get current Julian Day time. + @item julian_centuries() Get current Julian Centuries time (100 Julian days since J2000.) @end table @@ -167,29 +183,39 @@ Julian Centuries. These are low-level functions. @table @code @item sun_geometric_mean_longitude(t) Calculates the Sun's geometric mean longitude. + @item sun_geometric_mean_anomaly(t) Calculates the Sun's geometric mean anomaly, in radians. + @item earth_orbit_eccentricity(t) Calculates the Earth's orbit eccentricity. + @item sun_equation_of_centre(t) Calculates the Sun's equation of the centre --- the difference between the true anomaly and the mean anomaly --- in radians. + @item sun_real_longitude(t) Calculates the Sun's real longitudinal position, in radians. + @item sun_apparent_longitude(t) Calculates the Sun's apparent longitudinal position, in radians. + @item mean_ecliptic_obliquity(t) Calculates the uncorrected mean ecliptic obliquity of the Sun's apparent motion without variation correction, in radians. + @item corrected_mean_ecliptic_obliquity(t) Calculates the mean ecliptic obliquity of the Sun's apparent motion with variation correction, in radians. + @item solar_declination(t) Calculates the Sun's declination, in radians. + @item equation_of_time(t) Calculates the equation of time --- the discrepancy between apparent and mean solar time --- in degrees. + @item hour_angle_from_elevation(latitude, declination, elevation) Calculates the solar hour angle, in radians, from the Sun's elevation, in radians. The Sun's elevation is gived by the @@ -202,6 +228,7 @@ negative for westwards. @item declination The declination, in radians. @end table + @item elevation_from_hour_angle(latitude, declination, hour_angle) Calculates the Sun's elevation, in radians, from the solar hour angle, in radians. The solar hour angle is gived by the @@ -214,6 +241,7 @@ negative for westwards. @item declination The declination, in radians. @end table + @item time_of_solar_noon(t, longitude) Calculates the time, in Julian Centuries, of the solar noon the closest to the time @code{t}. This functions @@ -223,6 +251,7 @@ requires one additional parameter: The longitude in degrees eastwards from Greenwich, negative for westwards. @end table + @item time_of_solar_elevation(t, noon, latitude, longitude, elevation) Calculates the time, in Julian Centuries, the Sun has a specified apparent elevation, expressed in radians @@ -244,6 +273,7 @@ A time, in Julian Centuries, close to the sought time. @item noon The time, in Julian Centuries, of the closest solar noon. @end table + @item solar_elevation_from_time(t, latitude, longitude): Calculates the Sun's elevation, in radians, as apparent from a geographical position, expressed in degrees by the @@ -275,6 +305,7 @@ negative for westwards. The function also requires to the in Julian Centuries, provided via the parameter @code{t}. If @code{t} is @code{None}, the current time is used. + @item have_sunrise_and_sunset(latitude, t = None) Determine whether solar declination currently is so that there can be sunrises and sunsets. If not, @@ -285,6 +316,8 @@ provided via the parameter @code{latitude}, in degrees northwards from the equator, negative for southwards. If @code{t} is @code{None}, the current time is used. +This function returns a boolean. + @item is_summer(latitude, t = None) Determine whether it is summer on the hemisphere ont which you are located. @@ -294,6 +327,8 @@ provided via the parameter @code{latitude}, in degrees northwards from the equator, negative for southwards. If @code{t} is @code{None}, the current time is used. +This function returns a boolean. + @item is_winter(latitude, t = None) Determine whether it is winter on the hemisphere ont which you are located. @@ -302,6 +337,8 @@ provided via the parameter @code{t}, and the latitude, provided via the parameter @code{latitude}, in degrees northwards from the equator, negative for southwards. If @code{t} is @code{None}, the current time is used. + +This function returns a boolean. @end table @@ -309,6 +346,124 @@ If @code{t} is @code{None}, the current time is used. @node Prediction functions @chapter Prediction functions +Importing @code{solar_python} makes the following +solar data prediction functions available. All +parameters are of the type @code{float}, and +all functions return @code{float}. All parameters +named @code{t} is the time in Julian Centuries, +and the current time if set to @code{None}. Some +functions require the geographical position of +the observer. This latitude is provided via the +parameter @code{latitude} in degrees northwards +from the equator, negative for southwards. +This longitude is provided via the parameter +@code{longitude} in degrees eastwards from +Greenwich, negative for westwards. + +@table @code +@item solar_prediction(delta, requested, fun, epsilon = 0.000001, span = 0.01, t = None) +Predict the time point of the next or previous +time an arbitrary condition is meet. This function +returns the calculated time in Julian Centuries, +or @code{None} if the condition is not meet within +the specified timespan, specified by the parameter +@code{span} in Julian Centuries (@code{0.01} for +one year). + +The function shall find the input --- one parameter +in Julian Centuries --- for which the function-parameter +@code{fun} returns the value of @code{requested} within +an error tolerance of @code{epsilon}. + +The function uses the iteration step size @code{delta}. +If this value is negative, a past event will be determined, +and if it is positive, a future event will be predicted. + +@item future_past_equinox(delta, t = None) +Predict the time point, in Julian Centuries, of the +next or previous equinox. + +The function uses the iteration step size @code{delta}. +If this value is negative, a past event will be determined, +and if it is positive, a future event will be predicted. + +@item future_equinox(t = None) +Predict the time point, in Julian Centuries, of the +next equinox. + +@item past_equinox(t = None) +Predict the time point, in Julian Centuries, of the +previous equinox. + +@item future_past_solstice(delta, t = None) +Predict the time point, in Julian Centuries, of the +next or previous solstice. + +The function uses the iteration step size @code{delta}. +If this value is negative, a past event will be determined, +and if it is positive, a future event will be predicted. + +@item future_solstice(t = None) +Predict the time point, in Julian Centuries, of the +next solstice. + +@item past_solstice(t = None) +Predict the time point, in Julian Centuries, of the +previous solstice. + +@item future_past_elevation(delta, latitude, longitude, elevation, t = None) +Predict the time point, in Julian Centuries, of the next +or previous time the Sun reaches or reached a specific +elevation, specified in degrees via the parameter +@code{elevation}. @code{None} is returned if not found +withing a year. + +The function uses the iteration step size @code{delta}. +If this value is negative, a past event will be determined, +and if it is positive, a future event will be predicted. + +@item future_elevation(latitude, longitude, elevation, t = None) +Predict the time point, in Julian Centuries, of the next +time the Sun reaches a specific elevation, specified in +degrees via the parameter @code{elevation}. @code{None} +is returned if not found withing a year. + +@item past_elevation(latitude, longitude, elevation, t = None) +Predict the time point, in Julian Centuries, of the previous +time the Sun reached a specific elevation, specified in +degrees via the parameter @code{elevation}. @code{None} +is returned if not found withing a year. + +@item future_past_elevation_derivative(delta, latitude, longitude, derivative, t = None) +Predict the time point, in Julian Centuries, of the next or +previous time the Sun reaches or reached a specific elevation +derivative. @code{None} is returned if not found withing a +year. The sought derivative is specified via the parameter +@code{derivative}, expressed in degrees per Julian Century. + +The function uses the iteration step size @code{delta}. If +this value is negative, a past event will be determined, and +if it is positive, a future event will be predicted. + +@item future_elevation_derivative(latitude, longitude, derivative, t = None) +Predict the time point, in Julian Centuries, of the next time +the Sun reaches a specific elevation derivative. @code{None} +is returned if not found withing a year. The sought derivative +is specified via the parameter @code{derivative}, expressed in +degrees per Julian Century. + +@item past_elevation_derivative(latitude, longitude, derivative, t = None) +Predict the time point, in Julian Centuries, of the previous +time the Sun reached a specific elevation derivative. +@code{None} is returned if not found withing a year. The +sought derivative is specified via the parameter +@code{derivative}, expressed in degrees per Julian Century. + +@item sunrise_equation(latitude, longitude, t = None) +This algorithm is imprecise, gives an incorrent sunrise. +Its behaviour is not fully known. +@end table + @node Miscellaneous functions @@ -317,9 +472,10 @@ If @code{t} is @code{None}, the current time is used. Importing @code{solar_python} makes the following functions available: @table @code -@item radians(deg): +@item radians(deg) Convert an angle from degrees to radians. -@item degrees(rad): + +@item degrees(rad) Convert an angle from radians to degrees. @end table @@ -331,221 +487,3 @@ Convert an angle from radians to degrees. @bye - - - - ------------------------------ Prediction functions ----------------------------- - -def solar_prediction(delta, requested, fun, epsilon = 0.000001, span = 0.01, t = None): - ''' - Predict the time point of the next or previous - time an arbitrary condition is meet - - @param delta:float Iteration step size, negative for past - event, positive for future event - @param requested:float The value returned by `fun` for which to - calculate the time point of occurrence - @param fun:(t:float)→float Function that calculate the data of interest - @param epsilon:float Error tolerance for `requested` - @param span:float The number of Julian centuries (0,01 for - one year) to restrict the search to - @param t:float? The time in Julian Centuries, `None` for - the current time - @return :float? The calculated time point, `None` if none - were found within the specified time span - ''' - -def future_past_equinox(delta, t = None): - ''' - Predict the time point of the next or previous equinox - - @param delta:float Iteration step size, negative for - past event, positive for future event - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float The calculated time point - ''' - return solar_prediction(delta, 0, solar_declination, t = t) - - -def future_equinox(t = None): - ''' - Predict the time point of the next equinox - - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float The calculated time point - ''' - return future_past_equinox(0.01 / 2000, t) - - -def past_equinox(t = None): - ''' - Predict the time point of the previous equinox - - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float The calculated time point - ''' - return future_past_equinox(0.01 / -2000, t) - - - -def future_past_solstice(delta, t = None): - ''' - Predict the time point of the next or previous solstice - - @param delta:float Iteration step size, negative for - past event, positive for future event - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float The calculated time point - ''' - e = 0.00001 - fun = solar_declination - dfun = lambda t : (fun(t + e) - fun(t - e)) / 2 - return solar_prediction(delta, 0, dfun, t = t) - - -def future_solstice(t = None): - ''' - Predict the time point of the next solstice - - @param t:float? The time in Julian Centuries, - `None` for the current time - @return :float The calculated time point - ''' - return future_past_solstice(0.01 / 2000, t) - - -def past_solstice(t = None): - ''' - Predict the time point of the previous solstice - - @param t:float? The time in Julian Centuries, - `None` for the current time - @return :float The calculated time point - ''' - return future_past_solstice(0.01 / -2000, t) - - - -def future_past_elevation(delta, latitude, longitude, elevation, t = None): - ''' - Predict the time point of the next or previous time - the Sun reaches or reached a specific elevation - - @param delta:float Iteration step size, negative for past - event, positive for future event - @param latitude:float The latitude in degrees northwards from - the equator, negative for southwards - @param longitude:float The longitude in degrees eastwards from - Greenwich, negative for westwards - @param elevation:float The elevation of interest - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float? The calculated time point, `None` if - none were found within a year - ''' - fun = lambda t : solar_elevation(latitude, longitude, t) - return solar_prediction(delta, elevation, fun, t = t) - - -def future_elevation(latitude, longitude, elevation, t = None): - ''' - Predict the time point of the next time the Sun - reaches a specific elevation - - @param latitude:float The latitude in degrees northwards from - the equator, negative for southwards - @param longitude:float The longitude in degrees eastwards from - Greenwich, negative for westwards - @param elevation:float The elevation of interest - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float? The calculated time point, `None` if - none were found within a year - ''' - return future_past_elevation(0.01 / 2000, latitude, longitude, elevation, t) - - -def past_elevation(latitude, longitude, elevation, t = None): - ''' - Predict the time point of the previous time the Sun - reached a specific elevation - - @param latitude:float The latitude in degrees northwards from - the equator, negative for southwards - @param longitude:float The longitude in degrees eastwards from - Greenwich, negative for westwards - @param elevation:float The elevation of interest - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float? The calculated time point, `None` if - none were found within a year - ''' - return future_past_elevation(0.01 / -2000, latitude, longitude, elevation, t) - - - -def future_past_elevation_derivative(delta, latitude, longitude, derivative, t = None): - ''' - Predict the time point of the next or previous time the - Sun reaches or reached a specific elevation derivative - - @param delta:float Iteration step size, negative for past - event, positive for future event - @param latitude:float The latitude in degrees northwards from - the equator, negative for southwards - @param longitude:float The longitude in degrees eastwards from - Greenwich, negative for westwards - @param derivative:float The elevation derivative value of interest - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float? The calculated time point, `None` if - none were found within a year - ''' - fun = lambda t : solar_elevation(latitude, longitude, t) - dfun = lambda t : (fun(t + e) - fun(t - e)) / 2 - return solar_prediction(delta, derivative, dfun, t = t) - - -def future_elevation_derivative(latitude, longitude, derivative, t = None): - ''' - Predict the time point of the next time the - Sun reaches a specific elevation derivative - - @param latitude:float The latitude in degrees northwards from - the equator, negative for southwards - @param longitude:float The longitude in degrees eastwards from - Greenwich, negative for westwards - @param derivative:float The elevation derivative value of interest - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float? The calculated time point, `None` if - none were found within a year - ''' - return future_past_elevation_derivative(0.01 / 2000, latitude, longitude, derivative, t) - - -def past_elevation_derivative(latitude, longitude, derivative, t = None): - ''' - Predict the time point of the previous time - the Sun reached a specific elevation derivative - - @param latitude:float The latitude in degrees northwards from - the equator, negative for southwards - @param longitude:float The longitude in degrees eastwards from - Greenwich, negative for westwards - @param derivative:float The elevation derivative value of interest - @param t:float? The time in Julian Centuries, `None` - for the current time - @return :float? The calculated time point, `None` - if none were found within a year - ''' - return future_past_elevation_derivative(0.01 / -2000, latitude, longitude, derivative, t) - - -# This algorithm is imprecise, gives an incorrent sunrise and I do not fully know its behaviour -def sunrise_equation(latitude, longitude, t = None): |