Source code for astroplan.observer

# Licensed under a 3-clause BSD style license - see LICENSE.rst
from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

# Standard library
import datetime
import warnings

# Third-party
from astropy.coordinates import (EarthLocation, SkyCoord, AltAz, get_sun,
                                 get_moon, Angle, Latitude, Longitude,
                                 UnitSphericalRepresentation)
from astropy.extern.six import string_types
from astropy.utils import isiterable
from astropy.utils.compat.numpy import broadcast_to
import astropy.units as u
from astropy.time import Time
import numpy as np
import pytz

# Package
from .exceptions import TargetNeverUpWarning, TargetAlwaysUpWarning
from .moon import moon_illumination, moon_phase_angle
from .target import get_skycoord


__all__ = ["Observer", "MAGIC_TIME"]

MAGIC_TIME = Time(-999, format='jd')


def _generate_24hr_grid(t0, start, end, N, for_deriv=False):
    """
    Generate a nearly linearly spaced grid of time durations.

    The midpoints of these grid points will span times from ``t0``+``start``
    to ``t0``+``end``, including the end points, which is useful when taking
    numerical derivatives.

    Parameters
    ----------
    t0 : `~astropy.time.Time`
        Time queried for, grid will be built from or up to this time.

    start : float
        Number of days before/after ``t0`` to start the grid.

    end : float
        Number of days before/after ``t0`` to end the grid.

    N : int
        Number of grid points to generate

    for_deriv : bool
        Generate time series for taking numerical derivative (modify
        bounds)?

    Returns
    -------
    `~astropy.time.Time`
    """

    if for_deriv:
        time_grid = np.concatenate([[start - 1/(N-1)],
                                    np.linspace(start, end, N)[1:-1],
                                    [end + 1/(N-1)]])*u.day
    else:
        time_grid = np.linspace(start, end, N)*u.day

    # broadcast so grid is first index, and remaining shape of t0
    # falls in later indices. e.g. if t0 is shape (10), time_grid
    # will be shape (N, 10). If t0 is shape (5, 2), time_grid is (N, 5, 2)
    while time_grid.ndim <= t0.ndim:
        time_grid = time_grid[:, np.newaxis]
    # we want to avoid 1D grids since we always want to broadcast against targets
    if time_grid.ndim == 1:
        time_grid = time_grid[:, np.newaxis]
    return t0 + time_grid


[docs]class Observer(object): """ A container class for information about an observer's location and environment. Examples -------- We can create an observer at Subaru Observatory in Hawaii two ways. First, locations for some observatories are stored in astroplan, and these can be accessed by name, like so: >>> from astroplan import Observer >>> subaru = Observer.at_site("Subaru", timezone="US/Hawaii") To find out which observatories can be accessed by name, check out `~astropy.coordinates.EarthLocation.get_site_names`. Next, you can initialize an observer by specifying the location with `~astropy.coordinates.EarthLocation`: >>> from astropy.coordinates import EarthLocation >>> import astropy.units as u >>> location = EarthLocation.from_geodetic(-155.4761*u.deg, 19.825*u.deg, ... 4139*u.m) >>> subaru = Observer(location=location, name="Subaru", timezone="US/Hawaii") You can also create an observer without an `~astropy.coordinates.EarthLocation`: >>> from astroplan import Observer >>> import astropy.units as u >>> subaru = Observer(longitude=-155.4761*u.deg, latitude=19.825*u.deg, ... elevation=0*u.m, name="Subaru", timezone="US/Hawaii") """ @u.quantity_input(elevation=u.m) def __init__(self, location=None, timezone='UTC', name=None, latitude=None, longitude=None, elevation=0*u.m, pressure=None, relative_humidity=None, temperature=None, description=None): """ Parameters ---------- location : `~astropy.coordinates.EarthLocation` The location (latitude, longitude, elevation) of the observatory. timezone : str or `datetime.tzinfo` (optional) The local timezone to assume. If a string, it will be passed through ``pytz.timezone()`` to produce the timezone object. name : str A short name for the telescope, observatory or location. latitude : float, str, `~astropy.units.Quantity` (optional) The latitude of the observing location. Should be valid input for initializing a `~astropy.coordinates.Latitude` object. longitude : float, str, `~astropy.units.Quantity` (optional) The longitude of the observing location. Should be valid input for initializing a `~astropy.coordinates.Longitude` object. elevation : `~astropy.units.Quantity` (optional), default = 0 meters The elevation of the observing location, with respect to sea level. Defaults to sea level. pressure : `~astropy.units.Quantity` (optional) The ambient pressure. Defaults to zero (i.e. no atmosphere). relative_humidity : float (optional) The ambient relative humidity. temperature : `~astropy.units.Quantity` (optional) The ambient temperature. description : str (optional) A short description of the telescope, observatory or observing location. """ self.name = name self.pressure = pressure self.temperature = temperature self.relative_humidity = relative_humidity # If lat/long given instead of EarthLocation, convert them # to EarthLocation if location is None and (latitude is not None and longitude is not None): self.location = EarthLocation.from_geodetic(longitude, latitude, elevation) elif isinstance(location, EarthLocation): self.location = location else: raise TypeError('Observatory location must be specified with ' 'either (1) an instance of ' 'astropy.coordinates.EarthLocation or (2) ' 'latitude and longitude in degrees as ' 'accepted by astropy.coordinates.Latitude and ' 'astropy.coordinates.Latitude.') # Accept various timezone inputs, default to UTC if isinstance(timezone, datetime.tzinfo): self.timezone = timezone elif isinstance(timezone, string_types): self.timezone = pytz.timezone(timezone) else: raise TypeError('timezone keyword should be a string, or an ' 'instance of datetime.tzinfo') def __repr__(self): """ String representation of the `~astroplan.Observer` object. Examples -------- >>> from astroplan import Observer >>> keck = Observer.at_site("Keck", timezone="US/Hawaii") >>> print(keck) # doctest: +FLOAT_CMP <Observer: name='Keck', location (lon, lat, el)=(-155.478333333 deg, 19.8283333333 deg, 4160.0 m), timezone=<DstTzInfo 'US/Hawaii' LMT-1 day, 13:29:00 STD>> """ class_name = self.__class__.__name__ attr_names = ['name', 'location', 'timezone', 'pressure', 'temperature', 'relative_humidity'] attr_values = [getattr(self, attr) for attr in attr_names] attributes_strings = [] for name, value in zip(attr_names, attr_values): if value is not None: # Format location for easy readability if name == 'location': formatted_loc = ["{} {}".format(i.value, i.unit) for i in value.to_geodetic()] attributes_strings.append( "{} (lon, lat, el)=({})".format(name, ", ".join(formatted_loc))) else: if name != 'name': value = repr(value) else: value = "'{}'".format(value) attributes_strings.append("{}={}".format(name, value)) return "<{}: {}>".format(class_name, ",\n ".join(attributes_strings)) @classmethod
[docs] def at_site(cls, site_name, **kwargs): """ Initialize an `~astroplan.observer.Observer` object with a site name. Extra keyword arguments are passed to the `~astroplan.Observer` constructor (see `~astroplan.Observer` for available keyword arguments). Parameters ---------- site_name : str Observatory name, must be resolvable with `~astropy.coordinates.EarthLocation.get_site_names`. Returns ------- `~astroplan.observer.Observer` Observer object. Examples -------- Initialize an observer at Kitt Peak National Observatory: >>> from astroplan import Observer >>> import astropy.units as u >>> kpno_generic = Observer.at_site('kpno') >>> kpno_today = Observer.at_site('kpno', pressure=1*u.bar, temperature=0*u.deg_C) """ name = kwargs.pop('name', site_name) if 'location' in kwargs: raise ValueError("Location kwarg should not be used if " "initializing an Observer with Observer.at_site()") return cls(location=EarthLocation.of_site(site_name), name=name, **kwargs)
[docs] def astropy_time_to_datetime(self, astropy_time): """ Convert the `~astropy.time.Time` object ``astropy_time`` to a localized `~datetime.datetime` object. Timezones localized with `pytz`_. .. _pytz: https://pypi.python.org/pypi/pytz/ Parameters ---------- astropy_time : `~astropy.time.Time` Scalar or list-like. Returns ------- `~datetime.datetime` Localized datetime, where the timezone of the datetime is set by the ``timezone`` keyword argument of the `~astroplan.Observer` constructor. Examples -------- Convert an astropy time to a localized `~datetime.datetime`: >>> from astroplan import Observer >>> from astropy.time import Time >>> subaru = Observer.at_site("Subaru", timezone="US/Hawaii") >>> astropy_time = Time('1999-12-31 06:00:00') >>> print(subaru.astropy_time_to_datetime(astropy_time)) 1999-12-30 20:00:00-10:00 """ if not astropy_time.isscalar: return [self.astropy_time_to_datetime(t) for t in astropy_time] # Convert astropy.time.Time to a UTC localized datetime (aware) utc_datetime = pytz.utc.localize(astropy_time.utc.datetime) # Convert UTC to local timezone return self.timezone.normalize(utc_datetime)
[docs] def datetime_to_astropy_time(self, date_time): """ Convert the `~datetime.datetime` object ``date_time`` to a `~astropy.time.Time` object. Timezones localized with `pytz`_. If the ``date_time`` is naive, the implied timezone is the ``timezone`` structure of ``self``. Parameters ---------- date_time : `~datetime.datetime` or list-like Returns ------- `~astropy.time.Time` Astropy time object (no timezone information preserved). Examples -------- Convert a localized `~datetime.datetime` to a `~astropy.time.Time` object. Non-localized datetimes are assumed to be UTC. <Time object: scale='utc' format='datetime' value=1999-12-31 06:00:00> >>> from astroplan import Observer >>> import datetime >>> import pytz >>> subaru = Observer.at_site("Subaru", timezone="US/Hawaii") >>> hi_date_time = datetime.datetime(2005, 6, 21, 20, 0, 0, 0) >>> subaru.datetime_to_astropy_time(hi_date_time) <Time object: scale='utc' format='datetime' value=2005-06-22 06:00:00> >>> utc_date_time = datetime.datetime(2005, 6, 22, 6, 0, 0, 0, ... tzinfo=pytz.timezone("UTC")) >>> subaru.datetime_to_astropy_time(utc_date_time) <Time object: scale='utc' format='datetime' value=2005-06-22 06:00:00> """ if hasattr(date_time, '__iter__'): return Time([self.datetime_to_astropy_time(t) for t in date_time]) # For timezone-naive datetimes, assign local timezone if date_time.tzinfo is None: date_time = self.timezone.localize(date_time) return Time(date_time, location=self.location)
def _is_broadcastable(self, shp1, shp2): """Test if two shape tuples are broadcastable""" if shp1 == shp2: return True for a, b in zip(shp1[::-1], shp2[::-1]): if a == 1 or b == 1 or a == b: pass else: return False return True def _preprocess_inputs(self, time, target=None, grid_times_targets=False): """ Preprocess time and target inputs This routine takes the inputs for time and target and attempts to return a single `~astropy.time.Time` and `~astropy.coordinates.SkyCoord` for each argument, which may be non-scalar if necessary. time : `~astropy.time.Time` or other (see below) The time(s) to use in the calculation. It can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) target : `~astroplan.FixedTarget`, `~astropy.coordinates.SkyCoord`, or list The target(s) to use in the calculation. grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Useful for grid searches for rise/set times etc. """ # make sure we have a non-scalar time if not isinstance(time, Time): time = Time(time) if target is None: return time, None # convert any kind of target argument to non-scalar SkyCoord target = get_skycoord(target) if grid_times_targets: if target.isscalar: # ensure we have a (1, 1) shape coord target = SkyCoord(np.tile(target, 1))[:, np.newaxis] else: while target.ndim <= time.ndim: target = target[:, np.newaxis] elif not self._is_broadcastable(target.shape, time.shape): raise ValueError( 'Time and Target arguments cannot be broadcast against each other with shapes {} and {}'.format( time.shape, target.shape )) return time, target
[docs] def altaz(self, time, target=None, obswl=None, grid_times_targets=False): """ Get an `~astropy.coordinates.AltAz` frame or coordinate. If ``target`` is None, generates an altitude/azimuth frame. Otherwise, calculates the transformation to that frame for the requested ``target``. Parameters ---------- time : `~astropy.time.Time` or other (see below) The time at which the observation is taking place. Will be used as the ``obstime`` attribute in the resulting frame or coordinate. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) target : `~astroplan.FixedTarget`, `~astropy.coordinates.SkyCoord`, or list; defaults to `None` (optional) Celestial object(s) of interest. If ``target`` is `None`, return the `~astropy.coordinates.AltAz` frame without coordinates. obswl : `~astropy.units.Quantity` (optional) Wavelength of the observation used in the calculation. grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Useful for grid searches for rise/set times etc. Returns ------- `~astropy.coordinates.AltAz` If ``target`` is `None`, returns `~astropy.coordinates.AltAz` frame. If ``target`` is not `None`, returns the ``target`` transformed to the `~astropy.coordinates.AltAz` frame. Examples -------- Create an instance of the `~astropy.coordinates.AltAz` frame for an observer at Apache Point Observatory at a particular time: >>> from astroplan import Observer >>> from astropy.time import Time >>> from astropy.coordinates import SkyCoord >>> apo = Observer.at_site("APO") >>> time = Time('2001-02-03 04:05:06') >>> target = SkyCoord(0*u.deg, 0*u.deg) >>> altaz_frame = apo.altaz(time) Now transform the target's coordinates to the alt/az frame: >>> target_altaz = target.transform_to(altaz_frame) # doctest: +SKIP Alternatively, construct an alt/az frame and transform the target to that frame all in one step: >>> target_altaz = apo.altaz(time, target) # doctest: +SKIP """ if target is not None: time, target = self._preprocess_inputs(time, target, grid_times_targets) altaz_frame = AltAz(location=self.location, obstime=time, pressure=self.pressure, obswl=obswl, temperature=self.temperature, relative_humidity=self.relative_humidity) if target is None: # Return just the frame return altaz_frame else: return target.transform_to(altaz_frame)
[docs] def parallactic_angle(self, time, target, grid_times_targets=False): """ Calculate the parallactic angle. Parameters ---------- time : `~astropy.time.Time` Observation time. target : `~astroplan.FixedTarget` or `~astropy.coordinates.SkyCoord` or list Target celestial object(s). grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Returns ------- `~astropy.coordinates.Angle` Parallactic angle. Notes ----- The parallactic angle is the angle between the great circle that intersects a celestial object and the zenith, and the object's hour circle [1]_. .. [1] https://en.wikipedia.org/wiki/Parallactic_angle """ time, coordinate = self._preprocess_inputs(time, target, grid_times_targets) # Eqn (14.1) of Meeus' Astronomical Algorithms LST = time.sidereal_time('mean', longitude=self.location.lon) H = (LST - coordinate.ra).radian q = np.arctan(np.sin(H) / (np.tan(self.location.lat.radian) * np.cos(coordinate.dec.radian) - np.sin(coordinate.dec.radian)*np.cos(H)))*u.rad return Angle(q)
# Sun-related methods. @u.quantity_input(horizon=u.deg) def _horiz_cross(self, t, alt, rise_set, horizon=0*u.degree): """ Find time ``t`` when values in array ``a`` go from negative to positive or positive to negative (exclude endpoints) ``return_limits`` will return nearest times to zero-crossing. Parameters ---------- t : `~astropy.time.Time` Grid of N times, any shape. Search grid along first axis, e.g (N, ...) alt : `~astropy.units.Quantity` Grid of altitudes Depending on broadcasting we either have ndim >=3 and M targets along first axis, e.g (M, N, ...), or ndim = 2 and targets/times in last axis rise_set : {"rising", "setting"} Calculate either rising or setting across the horizon horizon : float Number of degrees above/below actual horizon to use for calculating rise/set times (i.e., -6 deg horizon = civil twilight, etc.) Returns ------- Returns the lower and upper limits on the time and altitudes of the horizon crossing. The altitude limits have shape (M, ...) and the time limits have shape (...). These arrays aresuitable for interpolation to find the horizon crossing time. """ # handle different cases by enforcing standard shapes on # the altitude grid finesse_time_indexes = False if alt.ndim == 1: raise ValueError('Must supply more at least a 2D grid of altitudes') elif alt.ndim == 2: # TODO: this test for ndim=2 doesn't work. if times is e.g (2,5) # then alt will have ndim=3, but shape (100, 2, 5) so grid # is in first index... ntargets = alt.shape[1] ngrid = alt.shape[0] unit = alt.unit alt = broadcast_to(alt, (ntargets, ngrid, ntargets)).T alt = alt*unit extra_dimension_added = True if t.shape[1] == 1: finesse_time_indexes = True else: extra_dimension_added = False output_shape = (alt.shape[0],) + alt.shape[2:] if rise_set == 'rising': # Find index where altitude goes from below to above horizon condition = (alt[:, :-1, ...] < horizon) * (alt[:, 1:, ...] > horizon) elif rise_set == 'setting': # Find index where altitude goes from above to below horizon condition = (alt[:, :-1, ...] > horizon) * (alt[:, 1:, ...] < horizon) noncrossing_indices = np.sum(condition, axis=1, dtype=np.intp) < 1 alt_lims1 = u.Quantity(np.zeros(output_shape), unit=u.deg) alt_lims2 = u.Quantity(np.zeros(output_shape), unit=u.deg) jd_lims1 = np.zeros(output_shape) jd_lims2 = np.zeros(output_shape) if np.any(noncrossing_indices): for target_index in set(np.where(noncrossing_indices)[0]): warnmsg = ('Target with index {} does not cross horizon={} within ' '24 hours'.format(target_index, horizon)) if (alt[target_index, ...] > horizon).all(): warnings.warn(warnmsg, TargetAlwaysUpWarning) else: warnings.warn(warnmsg, TargetNeverUpWarning) alt_lims1[np.nonzero(noncrossing_indices)] = np.nan alt_lims2[np.nonzero(noncrossing_indices)] = np.nan jd_lims1[np.nonzero(noncrossing_indices)] = np.nan jd_lims2[np.nonzero(noncrossing_indices)] = np.nan before_indices = np.array(np.nonzero(condition)) # we want to add an vector like (0, 1, ...) to get after indices after_indices = before_indices.copy() after_indices[1, :] += 1 al1 = alt[tuple(before_indices)] al2 = alt[tuple(after_indices)] # slice the time in the same way, but delete the object index before_time_index_tuple = np.delete(before_indices, 0, 0) after_time_index_tuple = np.delete(after_indices, 0, 0) if finesse_time_indexes: before_time_index_tuple[1:] = 0 after_time_index_tuple[1:] = 0 tl1 = t[tuple(before_time_index_tuple)] tl2 = t[tuple(after_time_index_tuple)] alt_lims1[tuple(np.delete(before_indices, 1, 0))] = al1 alt_lims2[tuple(np.delete(before_indices, 1, 0))] = al2 jd_lims1[tuple(np.delete(before_indices, 1, 0))] = tl1.utc.jd jd_lims2[tuple(np.delete(before_indices, 1, 0))] = tl2.utc.jd if extra_dimension_added: return (alt_lims1.diagonal(), alt_lims2.diagonal(), jd_lims1.diagonal(), jd_lims2.diagonal()) else: return alt_lims1, alt_lims2, jd_lims1, jd_lims2 @u.quantity_input(horizon=u.deg) def _two_point_interp(self, jd_before, jd_after, alt_before, alt_after, horizon=0*u.deg): """ Do linear interpolation between two ``altitudes`` at two ``times`` to determine the time where the altitude goes through zero. Parameters ---------- jd_before : `float` JD(UTC) before crossing event jd_after : `float` JD(UTC) after crossing event alt_before : `~astropy.units.Quantity` altitude before crossing event alt_after : `~astropy.units.Quantity` altitude after crossing event horizon : `~astropy.units.Quantity` Solve for the time when the altitude is equal to reference_alt. Returns ------- t : `~astropy.time.Time` Time when target crosses the horizon """ slope = (alt_after-alt_before)/((jd_after - jd_before)*u.d) crossing_jd = (jd_after*u.d - ((alt_after - horizon)/slope)) crossing_jd[np.isnan(crossing_jd)] = u.d*MAGIC_TIME.jd return np.squeeze(Time(crossing_jd, format='jd')) def _altitude_trig(self, LST, target, grid_times_targets=False): """ Calculate the altitude of ``target`` at local sidereal times ``LST``. This method provides a factor of ~3 speed up over calling `altaz`, and inherently does *not* take the atmosphere into account. Parameters ---------- LST : `~astropy.time.Time` Local sidereal times (array) target : {`~astropy.coordinates.SkyCoord`, `FixedTarget`} or similar Target celestial object's coordinates. grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Useful for grid searches for rise/set times etc. Returns ------- alt : `~astropy.unit.Quantity` Array of altitudes """ LST, target = self._preprocess_inputs(LST, target, grid_times_targets) alt = np.arcsin(np.sin(self.location.lat.radian) * np.sin(target.dec) + np.cos(self.location.lat.radian) * np.cos(target.dec) * np.cos(LST.radian - target.ra.radian)) return alt def _calc_riseset(self, time, target, prev_next, rise_set, horizon, N=150, grid_times_targets=False): """ Time at next rise/set of ``target``. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) target : `~astropy.coordinates.SkyCoord` Position of target or multiple positions of that target at multiple times (if target moves, like the Sun) prev_next : str - either 'previous' or 'next' Test next rise/set or previous rise/set rise_set : str - either 'rising' or 'setting' Compute prev/next rise or prev/next set horizon : `~astropy.units.Quantity` Degrees above/below actual horizon to use for calculating rise/set times (i.e., -6 deg horizon = civil twilight, etc.) N : int Number of altitudes to compute when searching for rise or set. grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Returns ------- ret1 : `~astropy.time.Time` Time of rise/set """ if not isinstance(time, Time): time = Time(time) if prev_next == 'next': times = _generate_24hr_grid(time, 0, 1, N) else: times = _generate_24hr_grid(time, -1, 0, N) altaz = self.altaz(times, target, grid_times_targets=grid_times_targets) altitudes = altaz.alt al1, al2, jd1, jd2 = self._horiz_cross(times, altitudes, rise_set, horizon) return self._two_point_interp(jd1, jd2, al1, al2, horizon=horizon) def _calc_transit(self, time, target, prev_next, antitransit=False, N=150, grid_times_targets=False): """ Time at next transit of the meridian of `target`. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) target : `~astropy.coordinates.SkyCoord` Position of target or multiple positions of that target at multiple times (if target moves, like the Sun) prev_next : str - either 'previous' or 'next' Test next rise/set or previous rise/set antitransit : bool Toggle compute antitransit (below horizon, equivalent to midnight for the Sun) N : int Number of altitudes to compute when searching for rise or set. grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Returns ------- ret1 : `~astropy.time.Time` Time of transit/antitransit """ # TODO FIX BROADCASTING HERE if not isinstance(time, Time): time = Time(time) if prev_next == 'next': times = _generate_24hr_grid(time, 0, 1, N, for_deriv=True) else: times = _generate_24hr_grid(time, -1, 0, N, for_deriv=True) # The derivative of the altitude with respect to time is increasing # from negative to positive values at the anti-transit of the meridian if antitransit: rise_set = 'rising' else: rise_set = 'setting' altaz = self.altaz(times, target, grid_times_targets=grid_times_targets) altitudes = altaz.alt if altitudes.ndim > 2: # shape is (M, N, ...) where M is targets and N is grid d_altitudes = altitudes.diff(axis=1) else: # shape is (N, M) where M is targets and N is grid d_altitudes = altitudes.diff(axis=0) dt = Time((times.jd[1:] + times.jd[:-1])/2, format='jd') horizon = 0*u.degree # Find when derivative passes through zero al1, al2, jd1, jd2 = self._horiz_cross(dt, d_altitudes, rise_set, horizon) return self._two_point_interp(jd1, jd2, al1, al2, horizon=horizon) def _determine_which_event(self, function, args_dict): """ Run through the next/previous/nearest permutations of the solutions to `function(time, ...)`, and return the previous/next/nearest one specified by the args stored in args_dict. """ time = args_dict.pop('time', None) target = args_dict.pop('target', None) which = args_dict.pop('which', None) horizon = args_dict.pop('horizon', None) rise_set = args_dict.pop('rise_set', None) antitransit = args_dict.pop('antitransit', None) grid_times_targets = args_dict.pop('grid_times_targets', False) # Assemble arguments for function, depending on the function. if function == self._calc_riseset: def event_function(w): return function(time, target, w, rise_set, horizon, grid_times_targets=grid_times_targets) elif function == self._calc_transit: def event_function(w): return function(time, target, w, antitransit=antitransit, grid_times_targets=grid_times_targets) else: raise ValueError('Function {} not supported in ' '_determine_which_event.'.format(function)) if not isinstance(time, Time): time = Time(time) if which == 'next' or which == 'nearest': next_event = event_function('next') if which == 'next': return next_event if which == 'previous' or which == 'nearest': previous_event = event_function('previous') if which == 'previous': return previous_event if which == 'nearest': mask = abs(time - previous_event) < abs(time - next_event) return Time(np.where(mask, previous_event.utc.jd, next_event.utc.jd), format='jd') raise ValueError('"which" kwarg must be "next", "previous" or ' '"nearest".') @u.quantity_input(horizon=u.deg)
[docs] def target_rise_time(self, time, target, which='nearest', horizon=0*u.degree, grid_times_targets=False): """ Calculate rise time. Compute time of the next/previous/nearest rise of the ``target`` object, where "rise" is defined as the time when the ``target`` transitions from altitudes below the ``horizon`` to above the ``horizon``. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) target : coordinate object (i.e. `~astropy.coordinates.SkyCoord`, `~astroplan.FixedTarget`) or list Target celestial object(s) which : {'next', 'previous', 'nearest'} Choose which sunrise relative to the present ``time`` would you like to calculate horizon : `~astropy.units.Quantity` (optional), default = zero degrees Degrees above/below actual horizon to use for calculating rise/set times (i.e., -6 deg horizon = civil twilight, etc.) grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Returns ------- `~astropy.time.Time` Rise time of target Examples -------- Calculate the rise time of Rigel at Keck Observatory: >>> from astroplan import Observer, FixedTarget >>> from astropy.time import Time >>> time = Time("2001-02-03 04:05:06") >>> target = FixedTarget.from_name("Rigel") >>> keck = Observer.at_site("Keck") >>> rigel_rise_time = keck.target_rise_time(time, target, which="next") >>> print("ISO: {0.iso}, JD: {0.jd}".format(rigel_rise_time)) # doctest: +FLOAT_CMP ISO: 2001-02-04 00:51:23.330, JD: 2451944.53569 """ return self._determine_which_event(self._calc_riseset, dict(time=time, target=target, which=which, rise_set='rising', horizon=horizon, grid_times_targets=grid_times_targets))
@u.quantity_input(horizon=u.deg)
[docs] def target_set_time(self, time, target, which='nearest', horizon=0*u.degree, grid_times_targets=False): """ Calculate set time. Compute time of the next/previous/nearest set of ``target``, where "set" is defined as when the ``target`` transitions from altitudes above ``horizon`` to below ``horizon``. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) target : coordinate object (i.e. `~astropy.coordinates.SkyCoord`, `~astroplan.FixedTarget`) or list Target celestial object(s) which : {'next', 'previous', 'nearest'} Choose which sunset relative to the present ``time`` would you like to calculate horizon : `~astropy.units.Quantity` (optional), default = zero degrees Degrees above/below actual horizon to use for calculating rise/set times (i.e., -6 deg horizon = civil twilight, etc.) grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Returns ------- `~astropy.time.Time` Set time of target. Examples -------- Calculate the set time of Rigel at Keck Observatory: >>> from astroplan import Observer, FixedTarget >>> from astropy.time import Time >>> time = Time("2001-02-03 04:05:06") >>> target = FixedTarget.from_name("Rigel") >>> keck = Observer.at_site("Keck") >>> rigel_set_time = keck.target_set_time(time, target, which="next") >>> print("ISO: {0.iso}, JD: {0.jd}".format(rigel_set_time)) # doctest: +FLOAT_CMP ISO: 2001-02-03 12:29:34.768, JD: 2451944.02054 """ return self._determine_which_event(self._calc_riseset, dict(time=time, target=target, which=which, rise_set='setting', horizon=horizon, grid_times_targets=grid_times_targets))
[docs] def target_meridian_transit_time(self, time, target, which='nearest', grid_times_targets=False): """ Calculate time at the transit of the meridian. Compute time of the next/previous/nearest transit of the ``target`` object. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) target : coordinate object (i.e. `~astropy.coordinates.SkyCoord`, `~astroplan.FixedTarget`) or list Target celestial object(s) which : {'next', 'previous', 'nearest'} Choose which sunrise relative to the present ``time`` would you like to calculate grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Returns ------- `~astropy.time.Time` Transit time of target Examples -------- Calculate the meridian transit time of Rigel at Keck Observatory: >>> from astroplan import Observer, FixedTarget >>> from astropy.time import Time >>> time = Time("2001-02-03 04:05:06") >>> target = FixedTarget.from_name("Rigel") >>> keck = Observer.at_site("Keck") >>> rigel_transit_time = keck.target_meridian_transit_time(time, target, ... which="next") >>> print("ISO: {0.iso}, JD: {0.jd}".format(rigel_transit_time)) # doctest: +FLOAT_CMP ISO: 2001-02-03 06:42:26.863, JD: 2451943.77948 """ return self._determine_which_event(self._calc_transit, dict(time=time, target=target, which=which, rise_set='setting', grid_times_targets=grid_times_targets))
[docs] def target_meridian_antitransit_time(self, time, target, which='nearest', grid_times_targets=False): """ Calculate time at the antitransit of the meridian. Compute time of the next/previous/nearest antitransit of the ``target`` object. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). target : coordinate object (i.e. `~astropy.coordinates.SkyCoord`, `~astroplan.FixedTarget`) or list Target celestial object(s) which : {'next', 'previous', 'nearest'} Choose which sunrise relative to the present ``time`` would you like to calculate grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Returns ------- `~astropy.time.Time` Antitransit time of target Examples -------- Calculate the meridian anti-transit time of Rigel at Keck Observatory: >>> from astroplan import Observer, FixedTarget >>> from astropy.time import Time >>> time = Time("2001-02-03 04:05:06") >>> target = FixedTarget.from_name("Rigel") >>> keck = Observer.at_site("Keck") >>> rigel_antitransit_time = keck.target_meridian_antitransit_time(time, target, ... which="next") >>> print("ISO: {0.iso}, JD: {0.jd}".format(rigel_antitransit_time)) # doctest: +FLOAT_CMP ISO: 2001-02-03 18:40:29.761, JD: 2451944.27812 """ return self._determine_which_event(self._calc_transit, dict(time=time, target=target, which=which, antitransit=True, rise_set='setting', grid_times_targets=grid_times_targets))
@u.quantity_input(horizon=u.deg)
[docs] def sun_rise_time(self, time, which='nearest', horizon=0*u.degree): """ Time of sunrise. Compute time of the next/previous/nearest sunrise, where sunrise is defined as when the Sun transitions from altitudes below ``horizon`` to above ``horizon``. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which sunrise relative to the present ``time`` would you like to calculate. horizon : `~astropy.units.Quantity` (optional), default = zero degrees Degrees above/below actual horizon to use for calculating rise/set times (i.e., -6 deg horizon = civil twilight, etc.) Returns ------- `~astropy.time.Time` Time of sunrise Examples -------- Calculate the time of the previous sunrise at Apache Point Observatory: >>> from astroplan import Observer >>> from astropy.time import Time >>> apo = Observer.at_site("APO") >>> time = Time('2001-02-03 04:05:06') >>> sun_rise = apo.sun_rise_time(time, which="previous") >>> print("ISO: {0.iso}, JD: {0.jd}".format(sun_rise)) # doctest: +SKIP ISO: 2001-02-02 14:02:50.554, JD: 2451943.08531 """ return self.target_rise_time(time, get_sun(time), which, horizon)
@u.quantity_input(horizon=u.deg)
[docs] def sun_set_time(self, time, which='nearest', horizon=0*u.degree): """ Time of sunset. Compute time of the next/previous/nearest sunset, where sunset is defined as when the Sun transitions from altitudes below ``horizon`` to above ``horizon``. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which sunset relative to the present ``time`` would you like to calculate horizon : `~astropy.units.Quantity` (optional), default = zero degrees Degrees above/below actual horizon to use for calculating rise/set times (i.e., -6 deg horizon = civil twilight, etc.) Returns ------- `~astropy.time.Time` Time of sunset Examples -------- Calculate the time of the next sunset at Apache Point Observatory: >>> from astroplan import Observer >>> from astropy.time import Time >>> apo = Observer.at_site("APO") >>> time = Time('2001-02-03 04:05:06') >>> sun_set = apo.sun_set_time(time, which="next") >>> print("ISO: {0.iso}, JD: {0.jd}".format(sun_set)) # doctest: +SKIP ISO: 2001-02-04 00:35:42.102, JD: 2451944.52479 """ return self.target_set_time(time, get_sun(time), which, horizon)
[docs] def noon(self, time, which='nearest'): """ Time at solar noon. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which noon relative to the present ``time`` would you like to calculate Returns ------- `~astropy.time.Time` Time at solar noon """ return self.target_meridian_transit_time(time, get_sun(time), which)
[docs] def midnight(self, time, which='nearest'): """ Time at solar midnight. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which noon relative to the present ``time`` would you like to calculate Returns ------- `~astropy.time.Time` Time at solar midnight """ return self.target_meridian_antitransit_time(time, get_sun(time), which)
# Twilight convenience functions
[docs] def twilight_evening_astronomical(self, time, which='nearest'): """ Time at evening astronomical (-18 degree) twilight. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observations. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which twilight relative to the present ``time`` would you like to calculate. Default is nearest. Returns ------- `~astropy.time.Time` Time of twilight """ return self.sun_set_time(time, which, horizon=-18*u.degree)
[docs] def twilight_evening_nautical(self, time, which='nearest'): """ Time at evening nautical (-12 degree) twilight. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observations. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which twilight relative to the present ``time`` would you like to calculate. Default is nearest. Returns ------- `~astropy.time.Time` Time of twilight """ return self.sun_set_time(time, which, horizon=-12*u.degree)
[docs] def twilight_evening_civil(self, time, which='nearest'): """ Time at evening civil (-6 degree) twilight. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observations. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which twilight relative to the present ``time`` would you like to calculate. Default is nearest. Returns ------- `~astropy.time.Time` Time of twilight """ return self.sun_set_time(time, which, horizon=-6*u.degree)
[docs] def twilight_morning_astronomical(self, time, which='nearest'): """ Time at morning astronomical (-18 degree) twilight. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observations. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which twilight relative to the present ``time`` would you like to calculate Returns ------- `~astropy.time.Time` Time of twilight """ return self.sun_rise_time(time, which, horizon=-18*u.degree)
[docs] def twilight_morning_nautical(self, time, which='nearest'): """ Time at morning nautical (-12 degree) twilight. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observations. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which twilight relative to the present ``time`` would you like to calculate. Default is nearest. Returns ------- `~astropy.time.Time` Time of twilight """ return self.sun_rise_time(time, which, horizon=-12*u.degree)
[docs] def twilight_morning_civil(self, time, which='nearest'): """ Time at morning civil (-6 degree) twilight. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observations. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). which : {'next', 'previous', 'nearest'} Choose which twilight relative to the present ``time`` would you like to calculate. Default is nearest. Returns ------- `~astropy.time.Time` Time of sunset """ return self.sun_rise_time(time, which, horizon=-6*u.degree)
# Moon-related methods.
[docs] def moon_rise_time(self, time, **kwargs): """ Returns the local moonrise time. The default moonrise returned is the next one to occur. Parameters ---------- time : `~astropy.time.Time` or other (see below) Keywords : str, optional previous next """ raise NotImplementedError()
[docs] def moon_set_time(self, time, **kwargs): """ Returns the local moonset time. The default moonset returned is the next one to occur. Parameters ---------- time : `~astropy.time.Time` or other (see below) This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). Keywords : str, optional previous next """ raise NotImplementedError()
[docs] def moon_illumination(self, time): """ Calculate the illuminated fraction of the moon. Parameters ---------- time : `~astropy.time.Time` or other (see below) This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). Returns ------- float Fraction of lunar surface illuminated Examples -------- How much of the lunar surface is illuminated at 2015-08-29 18:35 UTC, which we happen to know is the time of a full moon? >>> from astroplan import Observer >>> from astropy.time import Time >>> apo = Observer.at_site("APO") >>> time = Time("2015-08-29 18:35") >>> apo.moon_illumination(time) # doctest: +SKIP array([ 0.99972487]) """ if not isinstance(time, Time): time = Time(time) return moon_illumination(time)
[docs] def moon_phase(self, time=None): """ Calculate lunar orbital phase. For example, phase=2*pi is "new", phase=0 is "full". Parameters ---------- time : `~astropy.time.Time` or other (see below) This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). Returns ------- moon_phase_angle : float Orbital phase angle of the moon where 2*pi corresponds to new moon, zero corresponds to full moon. Examples -------- Calculate the phase of the moon at 2015-08-29 18:35 UTC. Near zero radians corresponds to a nearly full moon. >>> from astroplan import Observer >>> from astropy.time import Time >>> apo = Observer.at_site('APO') >>> time = Time('2015-08-29 18:35') >>> apo.moon_phase(time) # doctest: +SKIP <Quantity [ 0.03317537] rad> """ if time is not None and not isinstance(time, Time): time = Time(time) return moon_phase_angle(time)
[docs] def moon_altaz(self, time, ephemeris=None): """ Returns the position of the moon in alt/az. Parameters ---------- time : `~astropy.time.Time` or other (see below) This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object). ephemeris : str, optional Ephemeris to use. If not given, use the one set with ``astropy.coordinates.solar_system_ephemeris.set`` (which is set to 'builtin' by default). Returns ------- altaz : `~astropy.coordinates.SkyCoord` Position of the moon transformed to altitude and azimuth Examples -------- Calculate the altitude and azimuth of the moon at Apache Point Observatory: >>> from astroplan import Observer >>> from astropy.time import Time >>> apo = Observer.at_site("APO") >>> time = Time("2015-08-29 18:35") >>> altaz_moon = apo.moon_altaz(time) # doctest: +SKIP >>> print("alt: {0.alt}, az: {0.az}".format(altaz_moon)) # doctest: +SKIP alt: -63.72706397691421 deg, az: 345.3640380598265 deg """ if not isinstance(time, Time): time = Time(time) moon = get_moon(time, location=self.location, ephemeris=ephemeris) return self.altaz(time, moon)
@u.quantity_input(horizon=u.deg)
[docs] def target_is_up(self, time, target, horizon=0*u.degree, return_altaz=False, grid_times_targets=False): """ Is ``target`` above ``horizon`` at this ``time``? Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) target : coordinate object (i.e. `~astropy.coordinates.SkyCoord`, `~astroplan.FixedTarget`) or list Target celestial object(s) horizon : `~astropy.units.Quantity` (optional), default = zero degrees Degrees above/below actual horizon to use for calculating rise/set times (i.e., -6 deg horizon = civil twilight, etc.) return_altaz : bool (optional) Also return the '~astropy.coordinates.AltAz' coordinate. grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Returns ------- observable : boolean or np.ndarray(bool) True if ``target`` is above ``horizon`` at ``time``, else False. Examples -------- Are Aldebaran and Vega above the horizon at Apache Point Observatory at 2015-08-29 18:35 UTC? >>> from astroplan import Observer, FixedTarget >>> from astropy.time import Time >>> apo = Observer.at_site("APO") >>> time = Time("2015-08-29 18:35") >>> aldebaran = FixedTarget.from_name("Aldebaran") >>> vega = FixedTarget.from_name("Vega") >>> apo.target_is_up(time, aldebaran) True >>> apo.target_is_up(time, [aldebaran, vega]) array([ True, False], dtype=bool) """ if not isinstance(time, Time): time = Time(time) altaz = self.altaz(time, target, grid_times_targets=grid_times_targets) observable = altaz.alt > horizon if altaz.isscalar: observable = bool(observable) if not return_altaz: return observable else: return observable, altaz
@u.quantity_input(horizon=u.deg)
[docs] def is_night(self, time, horizon=0*u.deg, obswl=None): """ Is the Sun below ``horizon`` at ``time``? Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) horizon : `~astropy.units.Quantity` (optional), default = zero degrees Degrees above/below actual horizon to use for calculating day/night (i.e., -6 deg horizon = civil twilight, etc.) obswl : `~astropy.units.Quantity` (optional) Wavelength of the observation used in the calculation Returns ------- sun_below_horizon : bool or np.ndarray(bool) `True` if sun is below ``horizon`` at ``time``, else `False`. Examples -------- Is it "nighttime" (i.e. is the Sun below ``horizon``) at Apache Point Observatory at 2015-08-29 18:35 UTC? >>> from astroplan import Observer >>> from astropy.time import Time >>> apo = Observer.at_site("APO") >>> time = Time("2015-08-29 18:35") >>> apo.is_night(time) # doctest: +SKIP False """ if not isinstance(time, Time): time = Time(time) solar_altitude = self.altaz(time, target=get_sun(time), obswl=obswl).alt if solar_altitude.isscalar: return bool(solar_altitude < horizon) else: return solar_altitude < horizon
[docs] def local_sidereal_time(self, time, kind='apparent', model=None): """ Convert ``time`` to local sidereal time for observer. This is a thin wrapper around the `~astropy.time.Time.sidereal_time` method. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) kind : {'mean', 'apparent'} (optional) Passed to the ``kind`` argument of `~astropy.time.Time.sidereal_time` model : str or `None`; optional The precession/nutation model to assume - see `~astropy.time.Time.sidereal_time` for more details. Returns ------- `~astropy.coordinates.Longitude` Local sidereal time. """ if not isinstance(time, Time): time = Time(time) return time.sidereal_time(kind, longitude=self.location.lon, model=model)
[docs] def target_hour_angle(self, time, target, grid_times_targets=False): """ Calculate the local hour angle of ``target`` at ``time``. Parameters ---------- time : `~astropy.time.Time` or other (see below) Time of observation. This will be passed in as the first argument to the `~astropy.time.Time` initializer, so it can be anything that `~astropy.time.Time` will accept (including a `~astropy.time.Time` object) target : coordinate object (i.e. `~astropy.coordinates.SkyCoord`, `~astroplan.FixedTarget`) or list Target celestial object(s) grid_times_targets: bool If True, the target object will have extra dimensions packed onto the end, so that calculations with M targets and N times will return an (M, N) shaped result. Otherwise, we rely on broadcasting the shapes together using standard numpy rules. Returns ------- hour_angle : `~astropy.coordinates.Angle` The hour angle(s) of the target(s) at ``time`` """ time, target = self._preprocess_inputs(time, target, grid_times_targets) return Longitude(self.local_sidereal_time(time) - target.ra)
@u.quantity_input(horizon=u.degree)
[docs] def tonight(self, time=None, horizon=0 * u.degree, obswl=None): """ Return a time range corresponding to the nearest night This will return a range of `~astropy.time.Time` corresponding to the beginning and ending of the night. If in the middle of a given night, return times from `~astropy.time.Time.now` until the nearest `~astroplan.Observer.sun_rise_time` Parameters ---------- time : `~astropy.time.Time` (optional), default = `~astropy.time.Time.now` The start time for tonight, which is allowed to be arbitrary. See description above for behavior horizon : `~astropy.units.Quantity` (optional), default = zero degrees Degrees above/below actual horizon to use for calculating rise/set times (e.g., -6 deg horizon = civil twilight, etc.) obswl : `~astropy.units.Quantity` (optional) Wavelength of the observation used in the calculation Returns ------- times : `~astropy.time.Time` A tuple of times corresponding to the start and end of current night """ current_time = Time.now() if time is None else time night_mask = self.is_night(current_time, horizon=horizon, obswl=obswl) sun_set_time = self.sun_set_time(current_time, which='next', horizon=horizon) start_time = np.where(night_mask, current_time, sun_set_time) # np.where gives us a list of start Times - convert to Time object if not isinstance(start_time, Time): start_time = Time(start_time) end_time = self.sun_rise_time(start_time, which='next', horizon=horizon) return start_time, end_time