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.. _sunpy-how-to-access-coordinate-components:
****************************
Access coordinate components
****************************
Individual coordinates can be accessed via attributes on the `~astropy.coordinates.SkyCoord` object, but the names of the components of the coordinates can depend on the the frame and the chosen representation (e.g., Cartesian versus spherical).
`~sunpy.coordinates.Helioprojective`
====================================
For the helioprojective frame, the theta_x and theta_y components are accessed ``Tx`` and ``Ty``, respectively:
.. code-block:: python
>>> from astropy.coordinates import SkyCoord
>>> import astropy.units as u
>>> from sunpy.coordinates import frames
>>> c = SkyCoord(-500*u.arcsec, 100*u.arcsec, frame=frames.Helioprojective)
>>> c.Tx
<Longitude -500. arcsec>
>>> c.Ty
<Latitude 100. arcsec>
`~sunpy.coordinates.Heliocentric`
=================================
Heliocentric is typically used with Cartesian components:
.. code-block:: python
>>> c = SkyCoord(-72241.0*u.km, 361206.1*u.km, 589951.4*u.km, frame=frames.Heliocentric)
>>> c.x
<Quantity -72241. km>
>>> c.y
<Quantity 361206.1 km>
>>> c.z
<Quantity 589951.4 km>
`~sunpy.coordinates.HeliographicStonyhurst` and `~sunpy.coordinates.HeliographicCarrington`
===========================================================================================
Both of the heliographic frames have the components of latitude, longitude and radius:
.. code-block:: python
>>> c = SkyCoord(70*u.deg, -30*u.deg, 1*u.AU, frame=frames.HeliographicStonyhurst)
>>> c.lat
<Latitude -30. deg>
>>> c.lon
<Longitude 70. deg>
>>> c.radius
<Distance 1. AU>
Heliographic Stonyhurst, when used with Cartesian components, is known as Heliocentric Earth Equatorial (HEEQ).
Here's an example of how to use `~sunpy.coordinates.frames.HeliographicStonyhurst` for HEEQ coordinates:
.. code-block:: python
>>> c = SkyCoord(-72241.0*u.km, 361206.1*u.km, 589951.4*u.km,
... representation_type='cartesian', frame=frames.HeliographicStonyhurst)
>>> c.x
<Quantity -72241. km>
>>> c.y
<Quantity 361206.1 km>
>>> c.z
<Quantity 589951.4 km>
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