Corona Borealis or the Northern Crown is a little crown or horseshoe-shaped constellation visible in the western sky at nightfall in late August and September. Its most famous star is R Coronae Borealis, a variable star that can unexpectedly fade from sight. Bob King
Today’s topic is about a fascinating star called R Coronae Borealis (R CrB) in the constellation of the Northern Crown. Unlike most of the stars we see R CrB does not shine with a steady light night after night, year after year. Its brightness varies in a completely unpredictable way. Normally, the star shines at magnitude 6 — the naked-eye limit under dark skies — but every so often R fades away.
To find Corona Borealis, start with the Big Dipper and follow the arc of its handle to the bright orange star Arcturus, which stands about halfway up in the western sky at nightfall. Corona Borealis with its brightest star, Gemma, is located a fist directly above Arcturus. Once you’ve spotted the curlicue use the map below to pinpoint R CrB with binoculars. Stellarium
Within a week it becomes invisible without optical aid. And when faintest, around magnitude 15, it’s only visible in larger amateur ...