HADec#
- class astropy.coordinates.HADec(*args, **kwargs)[source]#
Bases:
BaseCoordinateFrame
A coordinate or frame in the Hour Angle-Declination system (Equatorial coordinates) with respect to the WGS84 ellipsoid. Hour Angle is oriented with respect to upper culmination such that the hour angle is negative to the East and positive to the West.
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 HADec to some other system.
- Parameters:
- data
BaseRepresentation
subclass instance A representation object or
None
to have no data (or use the coordinate component arguments, see below).- ha
Angle
, optional, keyword-only The Hour Angle for this object (
dec
must also be given andrepresentation
must be None).- dec
Angle
, optional, keyword-only The Declination for this object (
ha
must also be given andrepresentation
must be None).- distance
Quantity
[:ref: ‘length’], optional, keyword-only The Distance for this object along the line-of-sight.
- pm_ha_cosdec
Quantity
[:ref: ‘angular speed’], optional, keyword-only The proper motion in hour angle (including the
cos(dec)
factor) for this object (pm_dec
must also be given).- pm_dec
Quantity
[:ref: ‘angular speed’], optional, keyword-only The proper motion in declination for this object (
pm_ha_cosdec
must also be given).- radial_velocity
Quantity
[:ref: ‘speed’], optional, keyword-only The radial velocity of this object.
- representation_type
BaseRepresentation
subclass,str
, optional A representation class or string name of a representation class. This sets the expected input representation class, thereby changing the expected keyword arguments for the data passed in. For example, passing
representation_type='cartesian'
will make the classes expect position data with cartesian names, i.e.x, y, z
in most cases unless overridden viaframe_specific_representation_info
. To see this frame’s names, check out<this frame>().representation_info
.- differential_type
BaseDifferential
subclass,str
,dict
, optional A differential class or dictionary of differential classes (currently only a velocity differential with key ‘s’ is supported). This sets the expected input differential class, thereby changing the expected keyword arguments of the data passed in. For example, passing
differential_type='cartesian'
will make the classes expect velocity data with the argument namesv_x, v_y, v_z
unless overridden viaframe_specific_representation_info
. To see this frame’s names, check out<this frame>().representation_info
.- copybool, optional
If
True
(default), make copies of the input coordinate arrays. Can only be passed in as a keyword argument.
- data
- 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
[:ref: ‘pressure’] 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
[:ref: ‘temperature’] The ground-level temperature as an
Quantity
in deg C. This is necessary for performing refraction corrections.- relative_humidity
Quantity
[:ref: ‘dimensionless’] or number. The relative humidity as a dimensionless quantity between 0 to 1. This is necessary for performing refraction corrections.
- obswl
Quantity
[:ref: ‘length’] - The average wavelength of observations as an
Quantity
with length units. This is necessary for performing refraction corrections.
- The average wavelength of observations as an
- obstime
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 HADec and back to another frame can give highly discrepant results. For much better numerical stability, leave the
pressure
at0
(the default), thereby disabling the refraction correction and yielding “topocentric” equatorial coordinates.Attributes Summary
Default representation for differential data (e.g., velocity)
Default representation for position data
Mapping for frame-specific component names
The location on Earth of the observer
The reference time (e.g., time of observation)
The average wavelength of observations
The atmospheric pressure
The relative humidity
The ground-level temperature
Methods Summary
represent_as
(base[, s, in_frame_units])Ensure the wrap angle for any spherical representations.
Attributes Documentation
- default_differential#
Default representation for differential data (e.g., velocity)
- default_representation#
Default representation for position data
- frame_attributes = {'location': <astropy.coordinates.attributes.EarthLocationAttribute object>, 'obstime': <astropy.coordinates.attributes.TimeAttribute object>, 'obswl': <astropy.coordinates.attributes.QuantityAttribute object>, 'pressure': <astropy.coordinates.attributes.QuantityAttribute object>, 'relative_humidity': <astropy.coordinates.attributes.QuantityAttribute object>, 'temperature': <astropy.coordinates.attributes.QuantityAttribute object>}#
- frame_specific_representation_info#
Mapping for frame-specific component names
- location#
The location on Earth of the observer
No default value
- name = 'hadec'#
- obstime#
The reference time (e.g., time of observation)
No default value
- obswl#
The average wavelength of observations
Default: 1.0 micron
- pressure#
The atmospheric pressure
Default: 0.0 hPa
- relative_humidity#
The relative humidity
Default: 0.0
- temperature#
The ground-level temperature
Default: 0.0 deg_C
Methods Documentation