M41 (open cluster in Canis Major)
600: M41 image
M41 is a bright open cluster in Canis Major, so bright at magnitude 4.6 that it is occasionally a naked-eye object even from Bullington. M41 was discovered by Hodierna before 1654, and may have been known to Aristotle around 325 BCE. John Flamsteed certainly recorded it on February 16, 1702. le Gentil independently rediscovered it in 1749, and Messier added it to his catalog on January 16, 1765, 237 years ago today.
M41 comprises about 100 stars, the brightest of which is magnitude 6.9 and lies near the cluster’s center. M41 is a generally circular object, with an extent of about 38 arcminutes, or about a quarter again larger than the full moon. M41 is about a quarter billion years old, which puts it firmly into middle age for an open cluster.
610: M41 with binocular
The Astronomical League rates M41 as an “Easy” object with 7X50 binoculars, which indeed it is from Bullington. M41 lies about 4 degrees dead south of Sirius, the brightest star in the sky, so it’s easy to locate with binoculars or your telescope. At magnitude 4.6 and larger than the full moon, M41 is quite impressive in binoculars for an open cluster.
620: M41 with Telrad
It takes about 30 seconds to put M41 in your eyepiece field. Orient your Telrad as shown relative to Sirius to put M41 in your optical finder, where it will be quite prominent. Center M41 in the optical finder and use an eyepiece with a ¾ to 1-degree field to view at it.