The Pogson Method of Estimating Brightness

Norman Pogson is a well-known variable-star observer from the nineteenth century. He developed a procedure that differs from Argelander's method in that each step is determined to be precisely OTl. This method requires you to compare a variable star with a single comparison star using a previously memorized interval of O'Vl. You then observe the variable again, using a different comparison star. The variable's magnitude is deduced later. Your first observation might be recorded as A - 5,...