In October of 2014, when I moved to China, my hope was to catch more DSOs and complete the Messier list. All that I had then was a little more than 30 Messiers that I have seen from Bogota and my 15x70 Celestron Skymaster binoculars. Upon arriving, the list started to grow faster. During the first 7 months I added to the list my firsty galaxies (other than M31), some more globular clusters and a few open clusters. Later, I had completed 75% of the whole list, but truly with the binos the list contained only smudges, fuzzy cottonish balls and blurry like stellar objects.
I often like to compare binocular vs telescope views to show what magnification can do for one and this entry is one of those. This time the turn is for M46, a like nebular object in binoculars with a few stars inside it. In fact, Caroline Hershel decribed it in 1783 like this: “1 deg S following the nebula near the 2nd Navis [Puppis; M47], a Nebula the figure is done by memory”. If I did not know it was an open cluster I could think it was a nebula region like the type of Lagoon or Orion Nebula.
In middle of the very starry wide FOV, one can discern M47, a bright cluster at 2 o’ clock in the sketch. Right diagonal to it there is M46, a nebulous area with few resolvable stars.
Last december, I decided to apply more magnification to M46 and apart from resolving plenty of the individual stars in the cluster, I found a treasure among the stars: NGC 2438, a planetary nebula superimposed on the stellar cluster. With only 37.5x, but with averted vision, it was possible to see a circular and fuzzy smudge. With 100x it lost some of its surface brightness and looked like a ghosty and almost shapeless patch. In the sketch, it can be seen to the right of the cluster and it looks like a circular and dim fuzz.
M46 has a an estimated population of about 500 stars with 150 of the stars between magnitude 10th-13th. With direct vision I could see about 30 of those stars and much more with averted vision. Unfortunately, while using averted vision I got lost inside the cluster and decided it was time to finish the sketch.
And finally, here is the original sketch with some additional information about this observation.
Edited by: Jennifer Steinberg (editor in chief)