This conference proceeding reports some optical rotation curve data for some edge-on, late type (and presumably low surface brightness) galaxies. The idea of looking at edge-on galaxies is in principle a good one, since it can sometimes be difficult to constrain the inclinations of ragged looking low surface brightness galaxies. However, when you put the slit along such an object, you are integrating through the entire disk (until it becomes optically thick) along your line-of-sight. This is NOT the major axis rotation velocity you want to measure, as it has contributions from emission components which are moving in all directions, not just towards or away from you. The well known effect is to smear out the apparent rotation, making V(R) appear to rise less steeply than it really does - a systematic error from which it is impossible to recover.

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