Description

• Add support for rectangular “horizon” plots, like this one: https://earthsky.org/tonight/orion-the-hunter-ghost-of-the-summer-dawn/

  

• Options for background: gradient, solid color

• Options for horizon graphic: trees, hills, cityscape, custom

Ideas

• Could just be a special case of Lambert Az/Eq
• Separate plot type? e.g. Map, Optic, Horizon

p = sp.horizon(
			min_az=0,
			max_az=20,
			max_alt=50,
			...
)
# or ra/dec ?
# use stereo/zenith plots as a base