Open Cluster M46 and planetary nebula NGC 2438 April 10th 2013;  NELM 4.6;  Location: Moderately light polluted backyard in the foothills of western North Carolina. 

Telescope:  10-inch f/4.5 reflector 

Description:  Open cluster M46 is easily seen through an 8 x 50 finder, appearing as a hazy patch.  When observed with the 10-inch, it presents itself as very rich with a mostly round distribution of stars of similar magnitude.  In the central region is a small ring, devoid of stars, which is remarkably round.  It’s really interesting, but I’ve looked at this cluster many times over the years, and have never noted this circlet of stars before.  The superimposed planetary nebula, NGC 2438 is very dim and appears slightly elongated with a SE-NE orientation.  The edges of the ring at medium magnification appear very uneven in texture, and a dark center void is noticeable.  At 208x the 13M center star becomes visible. 

Telescope: 4-inch refractor stopped down to an effective aperture of 60 mm’s.  At 63x, the cluster appears rich, mostly round in shape, but very dim.  When increasing the magnification of 125x, I was very surprised to see the planetary nebula, NGC 2438, however, requiring averted vision. 

The following sketch was made using a 10-inch reflector, a No. 2 pencil, and an eraser on a blank 5 x 8 note card.  I inverted the color with a scanner to represent how the cluster and planetary appeared visually.

Roger Ivester

April 10th 2013

I observed open cluster M46 and planetary nebula NGC 2438 from my moderately light polluted backyard in the foothills of western North Carolina.  The NELM was about 4.6, and I used an f/4.5 reflector.

My first impression of the open cluster was just how dim it appeared 104x.  I could see what seemed to be over a hundred very faint stars and all but a few seemed to be of a similar magnitude.  After a  few minutes of careful viewing, the many stars began to look like crushed diamonds on black velvet.  When increasing the magnification to 208x the planetary nebula appeared as a very dim soap bubble. 

Debbie C. Ivester

Las Vegas Astronomical Society Observers Challenge:  To read the full report, click on the following link:

MARCH 2013 OBSERVERS CHALLENGE – M-46 NGC-2438

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