Messier Objects - M46

After the major cold snap and a cloudy warm front the weather was ideal for astronomy last Thursday evening.  I spent some time in the southern constellation of Puppis.  Puppis represents the poop deck of a giant ship in the sky.  The poop deck is the highest point on a ship and it typically covers a cabin; it is not where the latrines are kept.  Carina and Vela are also constellations that create the former overlarge constellation of the Argo Navis.  From the latitude of Calgary we are unable to see the complete constellation of Puppis but the northern reaches are definitely accessible.

The Milky Way traverses Puppis and thus there are many open clusters contained therein.  Messier 46 and Messier 47 are two of the largest clusters and are easily seen through binoculars and are spectacular through a telescope.

To find M46 I put my red dot finder on the sky's brightest star: Sirius.  I then moved the telescope eastward between γ and ι Canis Majoris until I found a dense cluster with many stars.  I estimated that there are several hundred stars making up the cluster.  My estimate of the size was 22' and the accepted value is 27'.  The faint stars in the outer edge of the cluster probably caused me to underestimate the size of it with a 8" aperture telescope.

M46 Observation Record

An interesting thing about M46 is that it contains a planetary nebula and a preplanetary nebula.  The planetary nebula NGC 2438 is not part of the cluster but aligned in the sky with it.  However, the preplanetary nebula known as the Calabash Nebula or Rotten Egg Nebula (due to its high sulphur content) is likely part of the cluster.  It shares the same distance, radial velocity and proper motion as its fellow members.

At the observatory last month I took a real good look at M46 and think I may have seen NGC 2438 as a faint fuzzy patch on the outer edge of the open cluster.  I was not able to see that from the city probably due to the light pollution.  I am hoping to image this cluster with my 11" and see if I can resolve NGC 2438 with longer exposures.  Also, as I image the Messier objects I will be able to fill in the blank image spot of my observation records!

The skies are supposed to be great this week, so if the wind abates and the clouds stay away there will be plenty of great things to see.  The RAO is having an open house on March 25 and there will be telescopes setup in Fish Creek Park on April 1.  These are great events to get the family out to see some amazing sights above us!