The evening sky this week is Moon-free, presenting a near-perfect opportunity to explore the marquee winter constellation, Orion. Given the season’s frequently chilly weather, your observing sessions are likely to be shorter than at other times of year. But if you plan carefully, you can see a lot in a little time especially if you utilize the unparalleled grab-and-go convenience of binoculars or a small telescope.
Let’s get warmed up with something really easy: Betelgeuse. As you may have read, the gentle red supergiant has been undergoing some interesting changes of late — it’s noticeably fainter than usual. Betelgeuse is a semiregular variable star that can shine be as bright as Rigel (magnitude 0.2), but at the moment at least, it’s clearly much, much fainter. When I checked last week, Betelgeuse was only a little brighter than Bellatrix (magnitude 1.6), and obviously fainter than Aldebaran (magnitude 0.9), in Taurus. My guesstimate placed Betelgeuse at around magnitude 1.4.
So what do optics bring to the party? I find that binoculars really do a nice job of enhancing the golden hue of Betelgeuse. Try bouncing back and forth between bluish white Rigel, and Betelgeuse — their contrasting tints help emphasize the subtle colors of both stars. Here’s another trick: defocus your binoculars slightly. Spreading out a star’s light helps make its color more conspicuous.