Sky This Week is brought to you in part by Celestron. Friday, May 29 An hour after sunset this evening, Cancer the Crab remains some 30° above the western horizon, available for viewing for a while longer before it’s lost to the summertime sky. This large, somewhat sparse constellation is located immediately to the upper left of Gemini, which hosts four bright points of light: the stars Castor and Pollux, the heads of the Twins, as well as the planets Jupiter and Venus. We’ll definitely be coming back to this constellation later this week.  But tonight, look to the Twins’ upper left for a rough, upside-down Y-shaped pattern of stars. We’re focusing in on the base of the Y’s stem, which appears at upper right and is marked by the 4th-magnitude star Iota (ι) Cancri. Sometimes called the “springtime Albireo,” this single point of light splits easily into two in any size telescope.…