>Before going through the list of what a bandpass can do, it's probably worth a sentence or two >explaining what physical concept the Bandpass class is modeling.

class docstring now begins:

```
    """Simple bandpass object, which models the transmission fraction of incident light as a
    function of wavelength, for either an entire optical path (e.g., atmosphere, reflecting and
    refracting optics, filters, CCD quantum efficiency), or some intermediate piece thereof.
    Bandpasses representing individual components may be combined through the `*` operator to form
    a new Bandpass object representing the composite optical path.
```