Archive for March 9, 2018

M41- Open Cluster in Canis Major-February 2018 Observer’s Challenge Report #108

March 9, 2018

FEBRUARY 2018 OBSERVERS CHALLENGE – M-041

Pencil sketch:  6-inch reflector @ 46x and 1.3º field of view: 

M41 Adjusted

Inverted colors

Rogers M-041 Inverted

Messier 41 (NGC 2287) at magnitude 4.5 is visible without optical aid. I often enjoy viewing this cluster with a pair of 7 x 21 mini-binoculars. It is easily located at about 4º south of Sirius, and NW of 6.0 magnitude 12 Canis Majoris.

A beautiful, but sparse cluster, very irregular shape, with several small chains of stars. The most noticeable star chains are on the SW and NE.

When using a 6-inch reflector, I can count ~60-70 stars. A small circlet of stars envelope the central region of the cluster. M41 contains the famous red star, known as the Espin star (HD 49091) magnitude of 6.9 and a K3 spectrum. The star was named after Rev. T.E. Espin (1858-1934.) I normally see this star as a deep-orange in color.    Roger Ivester

 

M41 image by James Dire:  

102mm (4-inch) f/7.9 refractor using a 0.8X focal reducer field flattener with an SBIG ST-2000XCM CCD camera. The exposure was 30 minutes. North is up, and east to the left.

M41

M41 is a beautiful galactic star cluster located 4° south of the bright star Sirius. The cluster can be seen naked eye from a dark site. It’s mag. 4.5 and is 39 arcminutes in diameter. It lies 2,350 light-years away

Aristotle noted M41 in 325BC as being a cloudy patch in the sky. The cluster was first cataloged by the Italian astronomer Giovanni Batista Hodierna in 1654, and then John Flamsteed in 1702. Charles Messier added it to his catalog in 1765.

M41 has about 100 stars. The brightest is a mag. 6.9 red giant star near the apparent center of the cluster, cataloged as HD49091. This K3 star has the brightness of 700 suns. The cluster is estimated to be 190 to 240 million years old and has a chemical composition similar to the sun.

The brightest star in the image is near the bottom edge, left of center. That star is 12 Canis Majoris, or HK Canis Majoris. HK is a mag. 6 blue giant star with a surface temperature of 18,000K. HK is only half the distance of M41 and thus is not a member of the cluster. The next brightest star in the image is the red giant HD49091, the red giant star near the center of the cluster.   James Dire 

 

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