These 2 objects are located in the constellation of Puppis at a declination of -38 degrees.  There are few other regions in the heavens with 2 lovely open clusters such as these in the same view.  I like that the 2 open clusters are similar in apparent size but offer such a contrast - loose colorful NGC 2451 vs. tight globular-like NGC 2477.

NGC 2451, just above image center, is a beautiful orange and blue open star cluster located 600 light years away. It is one of the earliest sky object discoveries, by Giovanni Battista Hodierna around 1650.  The brightest star in the center of the cluster, 3.6 magnitude c Puppis, has been called many different colors by astronomers over the years, from very red to orange to yellow. It looks orange to me in this calibrated image.

The cluster is 45 arc-minutes wide, corresponding to a diameter of about 6 lightyears.  Zoomed in, as seen in my original image of this object, there is not much to see.  But the wide view of this image brings in a few brighter blue stars from outside of the cluster, leading to a more pleasing panoramic view to my eye.

Like many other open clusters, astronomers have debated whether this truly is a cluster or simply a collection of bright stars. In 1994, German astronomers Siegfried Roser and Ulrich Bastian determined that many of the bright stars with similar proper motion belonged to a cluster called the Puppis Moving Group (NGC 2451a). They also proposed, and it was later confirmed, that a second distant cluster (NGC 2451b) exists further away at 1200 light years along the same line of sight. I cannot see 2 distinct clusters here.

This cluster has been nicknamed the Stinging Scorpion cluster, which is just plain stupid.

NGC 2477 is the open cluster at left.  It consists of about 300 stars located much further away, at 4000 light years away in the southern constellation of Puppis.  The cluster is 30 arc-minutes wide, corresponding to a diameter of about 36 light years.  This cluster is the 71st object in the Caldwell Catalog.

When I heard that some consider this to be one of the top open clusters in the sky, I was doubtful. It isn't even a Messier object. But I was wrong - this is a majestic cluster. It approaches a globular cluster in the sheer density of stars around the center, but because it is an open cluster, all of the stars are bright and resolved including many red giants. Although the magnitude of the brightest star is only 9.8, the magnitude of the cluster is a stunning 5.8, 4 magnitudes higher, because of the number of uniform bright stars in the cluster. The fact that it is so low in the southern sky (3 degrees transit above the Paris horizon) is the only thing which prevented Messier from adding it to his esteemed catalog.

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One piece of procedural advice – when uploading Astrobin images, on the Edit/Thumbnail page, there is a check box at the bottom labelled Sharpen Thumbnails.  DO NOT CHECK THIS BOX!  I had been checking it for all of my images from the beginning, thinking that it made the small thumbnail images a bit better.  I never closely examined the results, which I now have.  If you check this box, ALL of the images for that object post (except for the full size version) will be impacted, not just the small thumbnails as I had thought.  I verified this yesterday with Salvatore.  As a result, among other things, in the full screen image views the small stars (especially in a RASA image like this one) will be artificially and uniformly bright, and the dark, low contrast areas of the image will look blotchy.  I had been wondering why my image posts never looked as good as my original image.  The effect is subtle and may only be noticed by pixel peepers on large FOV images, but I can’t think of a reason why you would want to depreciate your images like that.  Salvatore said that he will update the language in the next Astrobin revision to more clearly describe the outcome of checking that box.