[BUG] mast.services._json_to_table fails with ValueError when Pan-STARRS returns literal 'None' strings in numeric columns

[AlexLee24]

When querying the Pan-STARRS catalog via astroquery.mast, the MAST server occasionally returns the literal string 'None' for missing values in numeric columns (e.g., magnitudes or error fields).

The internal helper function _json_to_table in astroquery/mast/services.py attempts to convert the data column to its expected NumPy type using .astype(col_type). If the column is expected to be a float64 but contains the string 'None', Python raises a ValueError: could not convert string to float: 'None', causing the entire query to crash.

Environment
OS: macOS 26.3 (Apple Silicon w/ osx-64 env)
Python version: 3.11
astroquery version: Latest
Service: astroquery.mast.Catalogs (Pan-STARRS)

Error message is like this:

Traceback (most recent call last):
  File "/Users/alexlee/Lab/autophot/test.py", line 17, in <module>
    raw_result = Catalogs.query_region(target_coords, radius=0.1*u.deg, catalog='Panstarrs')
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alexlee/miniconda3/envs/autophot_x86/lib/python3.11/site-packages/astroquery/utils/class_or_instance.py", line 25, in f
    return self.fn(obj, *args, **kwds)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alexlee/miniconda3/envs/autophot_x86/lib/python3.11/site-packages/astroquery/utils/process_asyncs.py", line 35, in newmethod
    result = self._parse_result(response, verbose=verbose)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alexlee/miniconda3/envs/autophot_x86/lib/python3.11/site-packages/astroquery/mast/collections.py", line 57, in _parse_result
    results_table = self._current_connection._parse_result(response, verbose=verbose)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alexlee/miniconda3/envs/autophot_x86/lib/python3.11/site-packages/astroquery/mast/services.py", line 237, in _parse_result
    result_table = _json_to_table(result, data_key=data_key)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alexlee/miniconda3/envs/autophot_x86/lib/python3.11/site-packages/astroquery/mast/services.py", line 106, in _json_to_table
    data_table.add_column(MaskedColumn(col_data.astype(col_type), name=col_name, mask=col_mask))
                                       ^^^^^^^^^^^^^^^^^^^^^^^^^
ValueError: could not convert string to float: 'None'

Python code to reproduce:

from astropy.coordinates import SkyCoord
import astropy.units as u
from astroquery.mast import Catalogs

target_coords = SkyCoord(ra=133.564987, dec=53.053127, unit="deg")
raw_result = Catalogs.query_region(target_coords, radius=0.1*u.deg, catalog='Panstarrs')

Thank you!

[snbianco]

Hi @AlexLee24! Thanks for reporting this. This issue should be fixed in #3492 . The fix is not in a release yet, but it is in the development version when you install directly from GitHub.

[AlexLee24]

Hi @AlexLee24! Thanks for reporting this. This issue should be fixed in #3492 . The fix is not in a release yet, but it is in the development version when you install directly from GitHub.

Thank you!