Chi Cygni: A Wide-Ranging Variable
Chi typically peaks near magnitude 5.2, after being only 13th magnitude just six months earlier. But the star can be up to two magnitudes brighter or fainter at maximum. For example, former Sky & Telescope editor Joseph Ashbrook found that Chi Cygni reached magnitude 4.6 on September 15, 1969. On at least one previous occasion it rose to 3.3, the brightest that any long-period variable has become except for Mira (Omicron Ceti).
In 2005 Chi Cygni came to maximum a little earlier than expected, peaking at about magnitude 5.3 in early July, judging from preliminary data of the American Association of Variable Star Observers (AAVSO). As of September 5, 2005, is was down to 7.9, still in reach of binoculars, and fading on schedule.
Use the chart here to keep watch on this wide-ranger! This star is one of those for which the AAVSO (www.aavso.org) seeks regular brightness estimates from its members continuing an observational series that runs back for centuries.