"""
=======================
Plotting the solar limb
=======================

This example demonstrates how you can draw the limb as seen by an arbitrary
observer.
"""
import matplotlib.pyplot as plt

import sunpy.map
from sunpy.coordinates import get_body_heliographic_stonyhurst
from sunpy.visualization import drawing

###############################################################################
# Let's download a magnetic field synoptic map and read it into a Map.

syn_map = sunpy.map.Map('http://jsoc.stanford.edu/data/hmi/synoptic/hmi.Synoptic_Mr.2191.fits')
syn_map.plot_settings['cmap'] = 'hmimag'
syn_map.plot_settings['norm'] = plt.Normalize(-1500, 1500)

###############################################################################
# Get coordinates for Earth and Mars at the date of the synoptic map
coords = {body: get_body_heliographic_stonyhurst(body, syn_map.date)
          for body in ['Earth', 'Mars']}

###############################################################################
# Now we can plot the map the the solar limb seen from these two coordinates.
# To create a legend for these limbs, we need to keep the patches returned by
# :func:`~sunpy.visualization.drawing.limb` and provide them to
# :meth:`~matplotlib.axes.Axes.legend`.
fig = plt.figure(figsize=(12, 5))
ax = fig.add_subplot(projection=syn_map)
im = syn_map.plot(axes=ax)

visible_limbs = []
for (body, coord), color in zip(coords.items(), ['tab:blue', 'tab:red']):
    v, _ = drawing.limb(ax, coord, color=color, label=f'Limb seen from {body}', linewidth=2)
    visible_limbs.append(v)

ax.legend(handles=visible_limbs)
plt.show()