Astropython.org visitor Danny writes:
"I have a question maybe somebody in this community can answer regarding coordinate lines drawn by Basemap [within Matplotlib].
Does anyone know if its possible to draw onto a map, grid lines (meridians and parallels) using a different coordinate system. For example an astronomical image plotted in equatorial coordinates with galactic parallels overlain. I am particularly attached to Basemap for plotting as it, among other things, provides all-sky projections like Mollweide.
Here is a crude example (not in moll, sadly):
The two coordinate systems are related by two rotations. I see how to define the latitude to achieve one, but not other.
Even if I could define a map with the appropriate tilts to achieve galactic coordinates, I had some trouble drawing a second map's grid lines over another underlying map. I tried defining a separate Basemap object with a different lat_0 but the drawparallels command seems to erase any previously drawn maps (hold=False?).
Thanks for any insights or solutions anyone might have."