http://books.google.com/books?id=hpnGyTJ-wAsC
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The philosophical transactions of the Royal Society of London, from their commencement in 1665 to the year 1800 (Google eBook)
http://books.google.com/books?pg=PA564&lpg=PA564&dq=alcor%20%22not%20the%20full%20moon%22&sig=Qv1t70QEfyeV1AcVhS4Nz7B5gpM&ei=z3mETrjPO6rYiALls-THDA&ct=result&id=hpnGyTJ-wAsC&ots=DFgoUImW5m&output=text
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The philosophical transactions of the Royal Society of London, from their ...
563 - 567
The manner of observation I conceive may be thus; having first made choice of the star we mean to observe, and having then considered where such star is to be seen in its greatest east or west azimuth; it may be then convenient to fix very firm and steadily, on some tower, steeple, or other high edifice, in a convenient situation, a good telescopic object-glass, in such position as may be proper for viewing that star; and at a due distance from it, near the ground, build some little stone-wall, or such like place, on which to fix the eye-glass so as to answer that object-glass; and having so adjusted it, as through both to see that star in its desired station, which may best be done while the star is to be seen by night in such situation, near the time of one of the solstices; let it be there fixed so firmly, as not to be disturbed, and the place so secured, as that none may come to disorder it, and care be taken to defend both the glasses, so as not to be endangered by wind and weather. This glass being once fixed, and a micrometer fitted to it, so as to have its threads perpendicular to the horizon, to avoid any inconvenience which might arise from diversity of refraction, if there be any, the star may then be viewed from time to time, for the following year or longer, to see if any change of azimuth can be observed.
The reason why I chiefly recommend, as a convenient star for this purpose, the shoulder of the Lesser Bear, is that there is adhering to it a very small star, which the Arabs call Alcor, (of which they have a proverbial saying, when they would describe a sharp-sighted man, that " he can discern the rider on the middle horse of the Wain and of one who pretends to see small things but overlooks much greater, that " he sees Alcor, but not the full moon,")
