Labelling axes on stereographc projection plots

[ursomniac]

So - using the nice example in the documentation, I generate a bunch of "things against the star field at a given (ra, dec) with a given FOV".

That all works as expected.

The challenge I have is that I would LIKE for the axes to be labeled with ra (x axis) and dec (y axis) - but of course those values aren't really linear (esp if you're centering closer to the poles), and ideally if you're using grid lines they also obviously won't be straight lines either.

I'm sure I could come up with some very convoluted way to do this (the grid lines aren't too hard to sort out, though it gets very "interesting" if Polaris is in/near the plot), but I was wondering if some other user might've found a comparatively elegant way to make this work... or could outline a strategy. So far the best I can think of is:

1. figure out the range of (ra, dec) for the 4 corners (also knowing the center coordinates, since that's a given)
2. (determine if there's a pole near/on the plot - but for the moment assume not)
3. sort out the ranges ∂RA, ∂Dec and come up with an appropriate "set" of axis values based on the range
4. manually put those ticks on the axes
5. (if doing grids) - step through the lines, compute the projected Star() values for each coordinate for each step - draw the lines

But one would like to hope that since this isn't an uncommon situation (it applies to maps on the earth as well as maps of the sky) that there might be some package-add/on that does the heavy lifting... :-)

[brandon-rhodes]

The AstroPy project has a nice-looking package called "WCSAxes":

https://docs.astropy.org/en/stable/visualization/wcsaxes/index.html

I once tried to use them to draw axes on a plot, but never quite got it working; you can see my commented-out code here:

python-skyfield/examples/charting.py

Line 14 in 52fd26c

# from astropy import wcs

Maybe I should return to that code sometime, and try to get it added to one of Skyfield's example plots in the documentation. Though it looks like it's no longer maintained primary as a standalone package, so might require users to do a huge AstroPy install? Maybe we should take a look at whether the standalone version is still viable.

[production23]

This is a great topic. RA/Dec axis labeling and projection overlays can get tricky fast, especially near the poles.

We're a platform for structured human-in-the-loop oversight across data modalities, from images and 3D mesh to scientific visualization.

We’re testing a pilot right now where our system suggests tick/grid overlays on sky plots (using WCSAxes or fallback transforms), and lets reviewers manually adjust/snap labels, then export SVG + JSON configs that are reproducible and ready for publication.

If you’re open to it, we’d love to use your stereographic Polaris example as a test case. We’ll provide a small helper script, reviewer UI, and export tools.

Happy to collaborate!
Aram, EvoLearns