AltAz¶
-
class
astropy.coordinates.
AltAz
(*args, **kwargs)[source] [edit on github]¶ Bases:
astropy.coordinates.BaseCoordinateFrame
A coordinate or frame in the Altitude-Azimuth system (Horizontal coordinates). Azimuth is oriented East of North (i.e., N=0, E=90 degrees).
This frame is assumed to include refraction effects if the
pressure
frame attribute is non-zero.The frame attributes are listed under Other Parameters, which are necessary for transforming from AltAz to some other system.
Parameters: representation :
BaseRepresentation
or NoneA representation object or None to have no data (or use the other keywords)
az :
Angle
, optional, must be keywordThe Azimuth for this object (
alt
must also be given andrepresentation
must be None).alt :
Angle
, optional, must be keywordThe Altitude for this object (
az
must also be given andrepresentation
must be None).distance :
Quantity
, optional, must be keywordThe Distance for this object along the line-of-sight.
pm_az_cosalt :
Quantity
, optional, must be keywordThe proper motion in azimuth (including the
cos(alt)
factor) for this object (pm_alt
must also be given).pm_alt :
Quantity
, optional, must be keywordThe proper motion in altitude for this object (
pm_az_cosalt
must also be given).radial_velocity :
Quantity
, optional, must be keywordThe radial velocity of this object.
copy : bool, optional
If
True
(default), make copies of the input coordinate arrays. Can only be passed in as a keyword argument.Other Parameters: obstime :
Time
The time at which the observation is taken. Used for determining the position and orientation of the Earth.
location :
EarthLocation
The location on the Earth. This can be specified either as an
EarthLocation
object or as anything that can be transformed to anITRS
frame.pressure :
Quantity
The atmospheric pressure as an
Quantity
with pressure units. This is necessary for performing refraction corrections. Setting this to 0 (the default) will disable refraction calculations when transforming to/from this frame.temperature :
Quantity
The ground-level temperature as an
Quantity
in deg C. This is necessary for performing refraction corrections.relative_humidity`` : numeric
The relative humidity as a number from 0 to 1. This is necessary for performing refraction corrections.
obswl :
Quantity
- The average wavelength of observations as an
Quantity
with length units. This is necessary for performing refraction corrections.
Notes
The refraction model is based on that implemented in ERFA, which is fast but becomes inaccurate for altitudes below about 5 degrees. Near and below altitudes of 0, it can even give meaningless answers, and in this case transforming to AltAz and back to another frame can give highly discrepent results. For much better numerical stability, leaving the
pressure
at0
(the default), disabling the refraction correction (yielding “topocentric” horizontal coordinates).Attributes Summary
default_differential
default_representation
frame_attributes
frame_specific_representation_info
location
name
obstime
obswl
pressure
relative_humidity
secz
Secant if the zenith angle for this coordinate, a common estimate of the airmass. temperature
zen
The zenith angle for this coordinate Attributes Documentation
-
default_differential
¶
-
default_representation
¶
-
frame_attributes
= OrderedDict([('obstime', <astropy.coordinates.frame_attributes.TimeFrameAttribute object>), ('location', <astropy.coordinates.frame_attributes.EarthLocationAttribute object>), ('pressure', <astropy.coordinates.frame_attributes.QuantityFrameAttribute object>), ('temperature', <astropy.coordinates.frame_attributes.QuantityFrameAttribute object>), ('relative_humidity', <astropy.coordinates.frame_attributes.FrameAttribute object>), ('obswl', <astropy.coordinates.frame_attributes.QuantityFrameAttribute object>)])¶
-
frame_specific_representation_info
¶
-
location
= None¶
-
name
= 'altaz'¶
-
obstime
= None¶
-
obswl
= <Quantity 1.0 micron>¶
-
pressure
= <Quantity 0.0 hPa>¶
-
relative_humidity
= 0¶
-
secz
¶ Secant if the zenith angle for this coordinate, a common estimate of the airmass.
-
temperature
= <Quantity 0.0 deg_C>¶
-
zen
¶ The zenith angle for this coordinate
- The average wavelength of observations as an