Unfortunately in this case, it was my laziness that caused the mistake rather than unit conversion: I looked at the WD01 table and assumed D03 was the same. Maybe I need an `astropy.be_lazy` module? :)

The interpolate won't *necessarily* raise an exception. Some scipy interpolators yield a constant value outside of the range. And at least some are configurable. If this one can be configured to raise an exception, I agree that would be best. (If coming directly from FITPACK, it might be cryptic, in which case you might have to catch and reraise.)