\input texinfo @c -*-texinfo-*- @c %**start of header @setfilename solar-python.info @settitle solar-python @afourpaper @documentencoding UTF-8 @documentlanguage en @finalout @c %**end of header @dircategory Astronomy @direntry * solar-python: (solar-python). Solar data calculation and prediction library for Python @end direntry @copying Copyright @copyright{} 2015 Mattias Andrée @quotation Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled ``GNU Free Documentation License''. @end quotation @end copying @ifnottex @node Top @top solar-python -- Solar data calculation and prediction library for Python @insertcopying @end ifnottex @titlepage @title solar-python @subtitle Solar data calculation and prediction library for Python @author by Mattias Andrée (maandree) @page @vskip 0pt plus 1filll @insertcopying @page @end titlepage @contents @menu * Overview:: Brief overview of @command{solar-python}. * Constants:: List of constants. * Calendar functions:: List of calendar functions. * Observation functions:: List of solar data observation functions. * Prediction functions:: List of solar data prediction functions. * Miscellaneous functions:: List of miscellaneous functions. * GNU Free Documentation License:: Copying and sharing this manual. @end menu @node Overview @chapter Overview @command{solar-python} is Python 3 library that can be used to calculate information about the Sun's position and related data and predict at when time solar events occur. Import the module @code{solar_python} to use the library. Documentation is available by the command @code{help} in python. @node Constants @chapter Constants Importing @code{solar_python} makes the following 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 @end table @node Calendar functions @chapter Calendar functions 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}. @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 @code{solar_python} also makes the following functions available. All parameters are of the type @code{float}, and all functions return @code{float}. @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 @node Observation functions @chapter Observation functions Importing @code{solar_python} makes the following solar data observation functions available. All parameters are of the type @code{float}, and all functions return @code{float}. All parameters named @code{t} or @code{noon} is the time in 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 parameter @code{elevation}. This functions requires two additional parameters: @table @code @item longitude The longitude in degrees eastwards from Greenwich, 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 parameter @code{hour_angle}. This functions requires two additional parameters: @table @code @item longitude The longitude in degrees eastwards from Greenwich, 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 requires one additional parameter: @table @code @item longitude 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 via the parameter @code{elevation}, at a geographical position, expressed in degrees by the parameters: @table @code @item latitude The latitude in degrees northwards from the equator, negative for southwards. @item longitude The longitude in degrees eastwards from Greenwich, negative for westwards. @end table @noindent The function require two additional parameter: @table @code @item t 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 parameters: @table @code @item latitude The latitude in degrees northwards from the equator, negative for southwards. @item longitude The longitude in degrees eastwards from Greenwich, negative for westwards. @end table @end table The library also provides the high-level functions: @table @code @item solar_elevation(latitude, longitude, t = None) Calculates the Sun's elevation, in degreesm as apparent from a geographical position, expressed in degrees by the parameters: @table @code @item latitude The latitude in degrees northwards from the equator, negative for southwards. @item longitude The longitude in degrees eastwards from Greenwich, negative for westwards. @end table @noindent 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, you either have 24-hour daytime or 24-hour nighttime. The function requires to the in Julian Centuries, 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. @item is_summer(latitude, t = None) Determine whether it is summer on the hemisphere ont which you are located. The function requires to the in Julian Centuries, 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. @item is_winter(latitude, t = None) Determine whether it is winter on the hemisphere ont which you are located. The function requires to the in Julian Centuries, 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. @end table @node Prediction functions @chapter Prediction functions @node Miscellaneous functions @chapter Miscellaneous functions Importing @code{solar_python} makes the following functions available: @table @code @item radians(deg): Convert an angle from degrees to radians. @item degrees(rad): Convert an angle from radians to degrees. @end table @node GNU Free Documentation License @appendix GNU Free Documentation License @include fdl.texinfo @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):