apply_space_motion without distance emits ErfaWarning

[orionlee]

Description

When SkyCoord.apply_space_motion() for a coordinate without distance specified, astropy emits the following warning:

WARNING: ErfaWarning: ERFA function "pmsafe" yielded 1 of "distance overridden (Note 6)" [astropy._erfa.core]

• The warning happened on the latest main. It was also on 4.1 release

• The issue seems to be related to Behaviour of apply_space_motion without distance without a distance #10092. But it appears that the resolution of Behaviour of apply_space_motion without distance without a distance #10092 does not make the warnings go away. The codes now just emit a different (albeit more comprehensible) warning.

• In jupyter, it emits two warnings that refer to the same problems:

WARNING: ErfaWarning: ERFA function "pmsafe" yielded 1077 of "distance overridden (Note 6)" [astropy._erfa.core]
WARNING:astropy:ErfaWarning: ERFA function "pmsafe" yielded 1077 of "distance overridden (Note 6)"

Expected behavior

The warning should not be there.

Steps to Reproduce

import astropy
from astropy import units as u
from astropy.coordinates import SkyCoord, Distance
from astropy.time import Time

c = SkyCoord(90 * u.deg, 45 * u.deg, pm_ra_cosdec=100 * u.mas / u.year, pm_dec= 1000 * u.mas / u.year,
             # uncomment distance to avoid
             #  WARNING: ErfaWarning: ERFA function "pmsafe" yielded 1 of "distance overridden (Note 6)" [astropy._erfa.core]
             # distance=Distance(parallax=768.5004 * u.mas),
             frame='icrs', obstime=Time("2000", format="decimalyear", scale="tt") + 0.5)
print(c.ra, c.dec)
new_c = c.apply_space_motion(new_obstime=Time(2021, format="decimalyear"))
print(new_c.ra, new_c.dec)

Running it will yield the following warning in apply_space_motion() call:

...\site-packages\erfa\core.py:155:  ErfaWarning: ERFA function "pmsafe" yielded 1 of "distance overridden (Note 6)"  ErfaWarning)

System Details

Windows-10-10.0.19041-SP0
Python 3.7.10 (default, Feb 26 2021, 13:06:18) [MSC v.1916 64 bit (AMD64)]
Numpy 1.20.2
astropy 4.3.dev1543+ga371a5903
Scipy 1.6.3
Matplotlib 3.4.1
erfa 1.7.3

[pllim]

What's your pyerfa version? cc @mhvk

[orionlee]

pyerfa version: on 1.7.3 (with main) and 1.7.2 (astropy 4.1 release)

I also tested with astropy main with erfa 2.0.0 : the same warning happened.

[rebekah9969]

• macOS Ventura Version 13.5.1
• Python 3.10.13
• numpy 1.23.5
• astropy 5.1

from astropy.coordinates import SkyCoord, Angle, Distance
import astropy.units as u
from astropy.time import Time
import lightkurve as lk
from lightkurve import *

epoch = Time(1569.4424277786259, scale="tdb", format="btjd")
equinox = Time(2000, format="jyear", scale="tt")

c = SkyCoord(
    ra=194.10778581007 * u.deg,
    dec=-27.41053258397 * u.deg,
    pm_ra_cosdec=-16.908 * u.mas/u.year,
    pm_dec=3.894* u.mas/u.year,
    frame="icrs",
    obstime=equinox,
) 

c1 = c.apply_space_motion(new_obstime=epoch)

I am finding the same behavior.
ErfaWarning: ERFA function "pmsafe" yielded 1 of "distance overridden (Note 6)" warnings.warn('ERFA function "{}" yielded {}'.format(func_name, wmsg),

Is there a solution to this please?