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Diffstat (limited to 'info')
| -rw-r--r-- | info/blueshift.texinfo | 250 |
1 files changed, 15 insertions, 235 deletions
diff --git a/info/blueshift.texinfo b/info/blueshift.texinfo index d130bb3..26c3a33 100644 --- a/info/blueshift.texinfo +++ b/info/blueshift.texinfo @@ -1278,247 +1278,27 @@ one argument, the POSIX time, that is, the number of seconds that have elapsed since 1970-(01)Jan-01 00:00:00 UTC, not counting leap seconds. -A set of functions that are used to calculate the Sun's -are provided: +Blueshift provides a set of functions, used to calculate +solar data, and solar data constants, by importing the +library @command{solar-python}. Refer to its documentation +for more details. +Blueshift also defines the function @table @code -@item julian_day_to_epoch(t) -Converts a Julian Day timestamp to a POSIX time timestamp. - -@item epoch_to_julian_day(t) -Converts a POSIX time timestamp to a Julian Day timestamp. - -@item julian_day_to_julian_centuries(t) -Converts a Julian Day timestamp to a Julian Centuries timestamp. - -@item julian_centuries_to_julian_day(t) -Converts a Julian Centuries timestamp to a Julian Day timestamp. - -@item epoch_to_julian_centuries(t) -Converts a POSIX time timestamp to a Julian Centuries timestamp. - -@item julian_centuries_to_epoch(t) -Converts a Julian Centuries timestamp to a POSIX time timestamp. - -@item epoch() -Returns the current time in POSIX time. - -@item julian_day() -Returns the current time in Julian Day time. - -@item julian_centuries() -Returns the current time in Julian Centuries time (100 Julian days since J2000.) - -@item radians(deg) -Converts from degrees to radians. - -@item degrees(rad) -Converts from radians to degrees. - -@item sun_geometric_mean_longitude(t) -Calculates the Sun's geometric mean longitude, in radians. - -@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 mean ecliptic obliquity, in radians, -of the Sun's apparent motion without variation correction. - -@item corrected_mean_ecliptic_obliquity(t) -Calculates the mean ecliptic obliquity, in radians, -of the Sun's apparent motion with variation correction. - -@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 from the Sun's elevation. - -@item elevation_from_hour_angle(latitude, declination, hour_angle) -Calculates the Sun's elevation from the solar hour angle. - -@item time_of_solar_noon(t, longitude) -Calculates the time of the closest solar noon. - -@item time_of_solar_elevation(t, noon, latitude, longitude, elevation) -Calculates the time the Sun has the apparent elevation -@code{elevation}, in degrees, at the geographical position -(@code{latitude}, @code{longitude}). @code{noon} is the -time the closest the solar noon. - -@item solar_elevation_from_time(t, latitude, longitude) -Calculates the Sun's elevation, in degrees, as apparent from the -geographical position (@code{latitude}, @code{longitude}). - -@item solar_elevation(latitude, longitude, t = None) -Calculates the same thing as @code{solar_elevation_from_time}, -except the time is optional and defaults to the current time. - -@item have_sunrise_and_sunset(latitude, t = None) -Determine whether you have sunrise and sunsets. - -@item is_summer(latitude, t = None) -Determine whether it is summer. - -@item is_winter(latitude, t = None) -Determine whether it is winter. - -@item future_past_elevation(delta, latitude, longitude, elevation, t = None) -Calculates the next or previous point in time the Sun's -elevation will be @code{elevation} degrees or was -@code{elevation} degrees at the geographical position -(@code{latitude}, @code{longitude}). The calculated -timepoint may actually be the current time, @code{t}. -If not time point can be found within a Julian year -@code{None} will be returned. This function uses binary -search to determine time point, because inverting -@code{solar_elevation} is unfeasible to do algebraically; -@code{delta} specified the size of the steps between the -timepoints that are tested to determine the timespan in -which to do the binary search. - -@item future_elevation(latitude, longitude, elevation, t = None) -Calculates the next point in time the Sun's elevation will -be @code{elevation} degrees at the geographical position -(@code{latitude}, @code{longitude}). The calculated -timepoint may actually be the current time, @code{t}. -If not time point can be found within a Julian year -@code{None} will be returned. This function uses - -@item past_elevation(latitude, longitude, elevation, t = None) -Calculates the previous point in time the Sun's elevation was -@code{elevation} degrees at the geographical position -(@code{latitude}, @code{longitude}). The calculated -timepoint may actually be the current time, @code{t}. -If not time point can be found within a Julian year -@code{None} will be returned. This function uses - -@item future_past_elevation_derivative(delta, latitude, longitude, derivative, t = None) -Similar to @code{future_past_elevation}, but calculates the -time point for a first derivative of the solar elevation. - -@item future_elevation_derivative(latitude, longitude, derivative, t = None) -Similar to @code{future_elevation}, but calculates the -time point for a first derivative of the solar elevation. - -@item past_elevation_derivative(latitude, longitude, derivative, t = None) -Similar to @code{past_elevation}, but calculates the -time point for a first derivative of the solar elevation. - -@item future_past_equinox(delta, t = None) -Similar to @code{future_past_elevation}, but calculates the -time point for an equinox. The result cannot be @code{None}. - -@item future_equinox(t = None) -Similar to @code{future_elevation}, but calculates the -time point for an equinox. The result cannot be @code{None}. - -@item past_equinox(t = None) -Similar to @code{past_elevation}, but calculates the -time point for an equinox. The result cannot be @code{None}. - -@item future_past_solstice(delta, t = None) -Similar to @code{future_past_elevation}, but calculates the -time point for a solstice. The result cannot be @code{None}. - -@item future_solstice(t = None) -Similar to @code{future_elevation}, but calculates the -time point for a solstice. The result cannot be @code{None}. - -@item past_solstice(t = None) -Similar to @code{past_elevation}, but calculates the -time point for a solstice. The result cannot be @code{None}. - -@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 by way of -binary searching. This conditions is satisfied if -@code{fun} of a timepoint equals @code{requested} -with a tolerance of @code{epsilon}. -@code{delta} specified the size of the steps between the -timepoints that are tested to determine the timespan in -which to do the binary search. This timespan is limited -to @code{span} with is a timespan in Julian Centuries; -0,01 is approximately one Gregorian year. -If no satisfactory timepoint can be found -within the specified span @code{None} is returned. - -@item ptime(t) +@item ptime(t : float) Prints a time, input in the Julian Centuries format, as a human-readable local time. - -@end table - -For all functions beneath @code{degrees}, @code{t} is the -time in Julian Centuries. All parameters are floating point -and may not be @code{None}, except for in @code{solar_elevation}, -as specified. - -Blueshift provides constants with important elevations of -the Sun during twilight. - -@table @code -@item SOLAR_ELEVATION_SUNSET_SUNRISE -The Sun's elevation at sunset and sunrise, -measured in degrees. - -@item SOLAR_ELEVATION_CIVIL_DUSK_DAWN -The Sun's elevation at civil dusk and civil dawn, -measured in degrees. - -@item SOLAR_ELEVATION_NAUTICAL_DUSK_DAWN -The Sun's elevation at nautical dusk and nautical -dawn, measured in degrees. - -@item SOLAR_ELEVATION_ASTRONOMICAL_DUSK_DAWN -The Sun's elevation at astronomical dusk and -astronomical dawn, measured in degrees. - -@item SOLAR_ELEVATION_RANGE_TWILIGHT -The Sun's lowest and highest elevation during all -periods of twilight, measured in degrees. - -@item SOLAR_ELEVATION_RANGE_CIVIL_TWILIGHT -The Sun's lowest and highest elevation during -civil twilight, measured in degrees. - -@item SOLAR_ELEVATION_RANGE_NAUTICAL_TWILIGHT -The Sun's lowest and highest elevation during -nautical twilight, measured in degrees. - -@item SOLAR_ELEVATION_RANGE_ASTRONOMICAL_TWILIGHT -The Sun's lowest and highest elevation during -astronomical twilight, measured in degrees. @end table -Blueshift provides a constant for the apparent -size of the Sun: @code{SOLAR_APPARENT_RADIUS}. -This constant can for example be used to get a -more accurate time when the night begins: rather -than simply saying that the night begins when -the Sun's apparent elevation is zero, you can say -that it begins when the Sun is no longer visible -at all, which is when the Sun's apparent elevation -is minus @code{SOLAR_APPARENT_RADIUS}. This value -is approximate. +Blueshift provides a constant, via @command{solar-python}, +for the apparent size of the Sun: @code{SOLAR_APPARENT_RADIUS}. +This constant can for example be used to get a more +accurate time when the night begins: rather than simply +saying that the night begins when the Sun's apparent +elevation is zero, you can say that it begins when the +Sun is no longer visible at all, which is when the Sun's +apparent elevation is minus @code{SOLAR_APPARENT_RADIUS}. +This value is approximate. @node Weather |