WARNING: Tried to get polar motions for times after IERS data is valid (need clearer message in warning on how to set software default)

[mzechmeister]

Currently, I get:

WARNING: Tried to get polar motions for times after IERS data is valid.
Defaulting to polar motion from the 50-yr mean for those.
This may affect precision at the 10s of arcsec level [astropy.coordinates.builtin_frames.utils]

raised in:

astropy/astropy/coordinates/builtin_frames/utils.py

Line 66 in 698d2e8

warnings.warn(wmsg.format('after'), AstropyWarning)

Which files do I need to update (and how) to resolve this warning?

The warning message could be made more user friendly.

[mzechmeister]

After quite some debugging, I think the problem was caused by an url with is not updated anymore: iers_conf.iers_auto_url = 'https://astroconda.org/aux/astropy_mirror/iers_a_1/finals2000A.all'
I switched to:
iers_conf.iers_auto_url = 'https://datacenter.iers.org/data/9/finals2000A.all'
Probably, I spotted the link here: astropy/astropy-iers-data#20.

Thus the warning could a give hint to check this file.

[pllim]

@mhvk , would an extra message to remind user to check conf.iers_auto_url completely cover such a problem or can this warning also be triggered by other causes?

[mhvk]

Yes, I think we could expand the warning. But we should also move the link back!

[pllim]

@mhvk , can you please clarify what you mean by "move the link back"? It's been a while since I looked at that part of the code.

[pllim]

@mzechmeister , are you interested to open a PR? https://docs.astropy.org/en/latest/development/workflow/development_workflow.html

[mzechmeister]

@pllim, I prefer here to only comment.

[mhvk]

@pllim - I have this vague memory that we had to change the link to this astroconda one because the regular finals200A.all became unavailable. Though I think that was actually a link to some .mil site to the astrometry group there. Of course, also fine to just ensure astroconda is kept up to date - I'm not sure who's responsible for that, though...

[pllim]

I am now confused. We don't point to astroconda.

astropy/astropy/utils/iers/iers.py

Line 42 in b237fbc

IERS_A_URL = 'ftp://anonymous:mail%40astropy.org@gdc.cddis.eosdis.nasa.gov/pub/products/iers/finals2000A.all' # noqa: E501

[mhvk]

@mzechmeister - now I'm super-confused too - where did your configuration come from? Is that default IERS_A_URL changed in making the conda astropy packages?

[mzechmeister]

It seems the problem started with #9427, and, I guess, I used astropy/astropy-iers-data#20 to solve my problem mzechmeister/serval#33 (comment). It's hard to keep track, when the url changes all the time.

[mhvk]

OK, that makes sense, and though the URL changes are largely out of our control, I'm sorry it led to your problems! Bottom line, I think, is that it would be useful for the warning message to point to some documentation about how to solve this...

[pllim]

All said though, it is recommended that you use the default, because we test it in the CI. We are not responsible for custom settings.