Limit extent of orthograpic projection (zooming) - cartopy

Question

I would like to produce orthographic (polar) plots of Antarctica that are 'zoomed' with respect to the default settings. By default I get this:
Antarctica polar
The following script produced this.
import cartopy.crs as ccrs
import matplotlib.pyplot as plt
ax = plt.axes(projection=ccrs.Orthographic(central_longitude=0.0, central_latitude=-90.))
ax.stock_img()
plt.show()
My best attempt to tell Cartopy 'limit the latitude to 60S to 90S' was:
ax.set_extent([-180,180,-60,-90], ccrs.PlateCarree())
unfortunately it does not give the desired result. Any ideas? Thanks in advance.

Answer 1

I'm not sure I fully understand what you're trying to do. Your example looks like a bounding box that was defined, but you'd like it rounded like your first example?
cartopy documentation has an example of this http://scitools.org.uk/cartopy/docs/latest/examples/always_circular_stereo.html:
import matplotlib.path as mpath
import matplotlib.pyplot as plt
import numpy as np
import cartopy.crs as ccrs
import cartopy.feature
def main():
fig = plt.figure(figsize=[10, 5])
ax1 = plt.subplot(1, 2, 1, projection=ccrs.SouthPolarStereo())
ax2 = plt.subplot(1, 2, 2, projection=ccrs.SouthPolarStereo(),
sharex=ax1, sharey=ax1)
fig.subplots_adjust(bottom=0.05, top=0.95,
left=0.04, right=0.95, wspace=0.02)
# Limit the map to -60 degrees latitude and below.
ax1.set_extent([-180, 180, -90, -60], ccrs.PlateCarree())
ax1.add_feature(cartopy.feature.LAND)
ax1.add_feature(cartopy.feature.OCEAN)
ax1.gridlines()
ax2.gridlines()
ax2.add_feature(cartopy.feature.LAND)
ax2.add_feature(cartopy.feature.OCEAN)
# Compute a circle in axes coordinates, which we can use as a boundary
# for the map. We can pan/zoom as much as we like - the boundary will be
# permanently circular.
theta = np.linspace(0, 2*np.pi, 100)
center, radius = [0.5, 0.5], 0.5
verts = np.vstack([np.sin(theta), np.cos(theta)]).T
circle = mpath.Path(verts * radius + center)
ax2.set_boundary(circle, transform=ax2.transAxes)
plt.show()
if __name__ == '__main__':
main()