Sunday, February 10, 2013

My first look at M41, the open cluster in Canis Major

Located about 4º directly below Sirius, the open cluster in Canis Major (M41) is easy to find through a camera lens or with the naked eye. Last night was my first time spotting the cluster, and I used my finger held at arms length to measure 1º increments below Sirius until I located the faint glob of stars.

Through a 300mm lens, I was able to see about a dozen or so dim stars. I shot a stack of photos to see if I would find any more stars hidden behind the noise. After a relatively short stacking session using DSS, here is what I came up with:

Open star cluster in canis major M41
89 subs, 17 darks, 21 bias, 300mm, 1.6 sec, f/5.6, ISO 1600

Stacking brought out most of the 100 or so stars that make up this cluster. Two articles I read mentioned curving rows of stars with a bright red star in the center.
"Many visual observers speak of seeing curved lines of stars in M41. Although they seem inconspicuous on photographs, the curves stand out strongly in my 10-inch [reflecting telescope], and the bright red star near the center of the cluster is prominent." (Source
"...look for a bright reddish star right in M41's heart. This star is surrounded by lots of fainter ones that seem to be arranged in curving rows, a peculiar feature noted also in many other open clusters." (Source)
Maybe it's the power of suggestion, but I do sort of see curving lines of stars surrounding a bright central star. Here is an overlay I made in Photoshop to illustrate one possible interpretation of the lines. Do you see them? Do you see different lines?

Curving lines of stars in open cluster M41
M41 with curving lines of stars outlined in Photoshop

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