FRIDAY, MAY 15 ■ This is the time of year when Leo the Lion starts walking downward toward the west, on his way to departing into the sunset in early summer. Right after dark, look for the brightest star fairly high in the southwest (well left of brighter Jupiter). That's Regulus, Leo's forefoot. Regulus is also the bottom of the Sickle of Leo: a backward question mark extending to the right or upper right, by a little more than a fist at arm's length. It outlines the lion's chest, and mane. Upper left of the Sickle, by a little more than a fist, is the long triangle forming Leo's rear end and tail. SATURDAY, MAY 16 ■ Vega is the brightest star in the east-northeast after dark. Look 14° (a little more than a fist at arm's length) to Vega's upper left for Eltanin, the 2nd-magnitude nose of Draco the Dragon. Closer above and upper left of Eltanin are the three fainter stars forming the rest of Draco's stick-figure head, which is also called the Lozenge.…