On the Border of Andromeda and Perseus

Nembus is a minor entry lying toward the boundary between Andromeda and Perseus, a crowded and much-observed part of the northern sky that holds the Andromeda Galaxy on one side and, on the other, the Perseus Double Cluster and the famous eclipsing variable Algol. The name is not securely traceable to any of the main naming traditions, and forms of it appear in the older star lists with variant spellings, a common condition among the minor entries. That instability is worth stating plainly rather than covering over: the fixed-star catalogues used in astrology were assembled by copying from earlier catalogues, and names that were already uncertain in one compilation were reproduced in the next. No traditional planetary nature is recorded for this star, and it carries no interpretive tradition of its own.

The crowded field between Andromeda and Perseus is exactly the kind of region where nineteenth-century compilers, working from several manuscript star-lists that did not always agree, could misattach a name to the wrong star entirely; Edward Ball Knobel's careful 1895 edition of the Al-Achsasi al-Mouakket catalogue was in part an attempt to sort out precisely this kind of confusion by returning to an original Arabic source rather than a chain of Latin copies of copies.