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STmag and ABmag conversions give ValueError

See original GitHub issue

The conversion test was done slightly differently in #5017, so this was not caught. Conversion works when .to() is invoked from the unit, not does not work when invoked from the Quantity but only if it was initialized using Quantity. Example below:

>>> from astropy import units as u

>>> wave = u.Quantity([4956.8, 4959.55, 4962.3], u.AA)
>>> flux_stmag = [12.41858665, 12.38919182, 12.41764379]
>>> photlam = u.photon / (u.cm ** 2 * u.s * u.AA)

>>> u.STmag.to(photlam, flux_stmag, u.spectral_density(wave))
array([ 0.0097654 ,  0.01003896,  0.00978473])

>>> q = flux_stmag * u.STmag
>>> q
<Magnitude [ 12.41858665, 12.38919182, 12.41764379] mag(ST)>
>>> q.to(photlam, u.spectral_density(wave))
<Quantity [ 0.0097654 , 0.01003896, 0.00978473] ph / (Angstrom cm2 s)>

>>> q = u.Quantity(flux_stmag, u.STmag)
>>> q
<Quantity [ 12.41858665, 12.38919182, 12.41764379] mag(ST)>
>>> q.to(photlam, u.spectral_density(wave))
.../astropy/units/quantity.py in to(self, unit, equivalencies)
    707         unit = Unit(unit)
    708         new_val = self.unit.to(unit, self.view(np.ndarray),
--> 709                                equivalencies=equivalencies)
    710         return self._new_view(new_val, unit)
    711 

.../astropy/units/core.py in to(self, other, value, equivalencies)
--> 997         return self._get_converter(other, equivalencies=equivalencies)(value)
    998 
    999     def in_units(self, other, value=1.0, equivalencies=[]):

.../astropy/units/core.py in _get_converter(self, other, equivalencies)
   1740         raise ValueError(
   1741             "The unit {0!r} is unrecognized.  It can not be converted "
-> 1742             "to other units.".format(self.name))
   1743 
   1744     def get_format_name(self, format):

ValueError: The unit 'mag(ST)' is unrecognized.  It can not be converted to other units.

Issue Analytics

State:
Created 7 years ago
Comments:11 (11 by maintainers)

Top GitHub Comments

1reaction

mhvkcommented, Jul 16, 2016

@pllim - see #5183.

And great to know that the magnitude code is being used so well, so that the bugs get shaken out!

0reactions

pllimcommented, Jul 21, 2016

@mhvk , no problem. I’ll open new issue if need be. Currently, I can work around the quirks.

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