air_pressure_column=None, latitude_const='49.088964', longitude_const='20.070236', temperature_const=0, elevation_const=952,

air_pressure_const=1010, twilight_const='-6', horizon_const='-0:34', duration=False):

'''

dusk_dawn_utc will give you the categories (strings) "night", "dusk", "day", "dawn" based on the variables

and optionally with the duration is a second variable.

The input time must be in UTC

Args:

datetime_utc, the column name containing the UTC time of the observation

If the *_column variables are not provided than it is assumed that these values are provides as constant

for all observations

latitude_column: the column name containing the latitude of the observation

longitude_column: the column name containing the longitude of the observation

temperature_column: the temperature in degrees celcius at the moment of the observation at the

location of the observation

elevation_column: the column name containing the number of meters above sealevel of the location of

the observation

air_pressure_column: the column name containing the air preassure at the moment of the observation on the

location

In case the variables are not present at the observation these values are provides as constant for

all observations

latitude_cons the latitude of the observation

longitude_const the longitude of the observation

temperature_const: the temperature in degrees celcius at the moment of the observation

elevation_const the number of meters above sealevel of the observation

air_pressure_const: the air preassure at the moment of the observation

constants for observation and twilight calculation

twilight_const='-6': the twilight start -6 is civil, -12 is nautic and -18 is astronomical

the value should be entered as a string ('-6', '-12'' '-18')

horizon_const='-0:34') the horizon attribute defines your horizon, the altitude of the upper limb of a body

at the moment you consider it to be rising and setting. The United States Naval Observatory,

rather than computing refraction dynamically, uses a constant estimate of 34’ of refraction

at the horizon.

duration: gives the timedelta between the events and gives how long the night, dusk, day and

dawn took. If "True" the function returns a second variable with the duration of the

observed dusk, day, dawn, night.

Returns:

a string with one of the labels "night", "dusk", "day", "dawn"

or when duration=True

returns a the label mentioned above and the duration

Raises:

KeyError: Raises an exception.

See https://rhodesmill.org/pyephem/quick.html'''

my_observer = ephem.Observer()

my_observer.date = datetime_utc

if latitude_column == None:

my_observer.lat = str(latitude_const)

else:

my_observer.lat = str(latitude_column)

if longitude_column == None:

my_observer.lon = str(longitude_const)

else:

my_observer.lon = str(longitude_column)

# %% these parameters are for super-precise estimates, not necessary.

if elevation_column==None:

my_observer.elevation = elevation_const

else:

my_observer.elevation = elevation_column

if air_pressure_column == None:

my_observer.pressure = air_pressure_const # millibar. The difference between the lowest ever observed (923.6) and the highest ever observed (1072) in Europe is 36 seconds later

else:

my_observer.pressure = air_pressure_column

if temperature_column==None:

my_observer.temp = temperature_const # deg. Celcius. The difference between 0 deg. Celcius and 50 deg. Celcius = 37 seconds later

else:

my_observer.temp = temperature_column

my_observer.horizon = str(horizon_const)

sun = ephem.Sun()

next_sunrise_utc = my_observer.next_rising(sun)

next_sunset_utc = my_observer.next_setting(sun)

if duration:

previous_sunrise_utc = my_observer.previous_rising(sun)

previous_sunset_utc = my_observer.previous_setting(sun)

else:

pass

#Relocate the horizon to get twilight times

#-6=civil twilight, -12=nautical, -18=astronomical

my_observer.horizon = str(twilight_const)

next_twilight_rise_utc = my_observer.next_rising(ephem.Sun(), use_center=True) #Begin dusk

next_twilight_set_utc =my_observer.next_setting (ephem.Sun(), use_center=True) #Begin dawn

if duration:

previous_twilight_rise_utc = my_observer.previous_rising(sun)

previous_twilight_set_utc = my_observer.previous_setting(sun)

else:

pass

result_dict= {

"next_twilight_rise_utc":next_twilight_rise_utc,

"next_sunrise_utc":next_sunrise_utc,

"next_sunset_utc":next_sunset_utc,

"next_twilight_set_utc":next_twilight_set_utc

}

result_lowest=min(result_dict, key=result_dict.get)

if result_lowest == "next_twilight_rise_utc":

result="night"

elif result_lowest == "next_sunrise_utc":

result = "dawn"

elif result_lowest == "next_sunset_utc":

result = "day"

elif result_lowest == "next_twilight_set_utc":

result = "dusk"

if duration:

if result == "night":

duration=str(timedelta(next_twilight_rise_utc-previous_twilight_set_utc))

elif result == "dusk":

duration=str(timedelta(next_sunrise_utc-previous_twilight_rise_utc))

elif result == "day":

duration=str(timedelta(next_sunset_utc-previous_sunrise_utc))

elif result == "dawn":

duration=str(timedelta(next_twilight_set_utc-previous_sunset_utc))

else:

result = 'Error defining the string dusk, day, dawn, night'

else:

pass

if duration:

return(result, duration)

else:

'''

convert_to_utc will return the UTC time from your datetime given the timezone of the observation.

Args:

datetime: a datetime variable

local_timezone: a string resembling the timezone of the time observation

Returns:

datetime in UTC

Raises:

KeyError: Raises an exception.

'''

datetime_utc=datetime.tz_localize(local_timezone).tz_convert("UTC")