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When characterizing a high resolution echelle spectrograph, for instance forprecise Doppler work, it is useful to observe featureless sources such asquartz lamps or hot stars to determine the response of the instrument. Suchsources provide a way to determine the blaze function of the orders,pixel-to-pixel variations in the detector, fringing in the system, and otherimportant characteristics. In practice, however, many B or early A stars do notprovide a smooth continuum, whether because they are not rotating rapidlyenough or for some other reason. In fact, we have found that publishedrotational velocities and temperatures are not a specific and sensitive guideto whether a star's continuum will be smooth. A useful resource for observers,therefore, is a list of "good" hot stars: bright, blue stars known empiricallyto have no lines or other spectral features beyond the Balmer series withminima below 95% of the continuum.  We have compiled a list of such stars visible from Northern Hemispheretelescopes. This list includes all stars listed in the Yale Bright Star Catalog(Hoffleit & Jaschek 1991) as being single with V < 5.5, v sin i > 175 km/s, anddeclination > -30, and many other hot stars that we have found useful forcalibration purposes.  The list here of "bad" stars may also be of interest in studies of hot,slowly rotating stars.

Some Bright Stars with Smooth Continua for Calibrating the Response of High Resolution Spectrographs