but but ... science shouldn't be about what we want, but what's physically right ;-) I think it's bad that there's no warning or exception in the IDL astrolib version. Maybe a compromise could be made with a keyword `warn_extension=True` - which then can be switched off when this clutters up the log. This way people get a slap on their wrist, but can switch that off (once their wrist hurts ;-) ).