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M35 & NGC 2158

Open Cluster
aka NGC 2168, Melotte 41, Collinder 82, Raab 31, OCL 466
RA: 06h08m51.9s, Dec: +2420'28" (2000) in Gemini
Integrated Visual Magnitude: 5.6
Apparent Diameter: 28'

Distance: 2800 ly

Age: 117 Myrs 

Minimum requirements to detect: any telescope under urban skies


M35 is a large open cluster in Gemini with many bright stars.  It is a favorite for small telescopes and is just visible to the unaided eye as a sparkling point of light.  Over a century ago Garrett P. Serviss wrote in Astronomy with an Opera-Glass, "No one can gaze upon this marvelous phenomenon, even with the comparatively low powers of an opera-glass, and reflect that all these swarming dots of light are really suns, without a stunning sense of the immensity of the material universe."

Yet, in a universe characterized by "billions", M35 lies only about 3000 light years away and is a mere 177 million years old.

This image from the DSS shows a 50' x' 50' field. North is down and east is to the right. Photographs do not do M35 (center) justice!  In the telescope, the nearby NGC 2158 (upper left) can be a difficult object.
Walter Scott Houston wrote of M35 as seen in a 10-inch, "The view was too beautiful to describe with mere words.  Bright stars were scattered with cosmic recklessness across the field, and it was difficult to establish where the cluster's edges dissolved into the stellar background.  There were dozens of curving star chains.  Everywhere I looked I could see between the stars into the black depths of infinity."

Although Scotty also wrote that, "M35 is one of the few clusters that loses its charm if you view it with too large a telescope," I was happy to see that it is still an excellent target for larger apertures.  My favorite view in my 18" was at 165x.  The many bright stars formed a tapestry that filled the field of view.  Still rich in stars, you could nonetheless scan in all directions and still be within the cluster.  So homogeneous are the colors of the stars that one of the brightest stood out although it sports only a very slight orange tint.


The view in a 6-inch at 55x.  North is down, east is right,

NGC 2158 is a much smaller and fainter open cluster that lies quite nearby.  Comparing this cluster to its neighbor is a wonderful study in contrast.  NGC 2158 has a beauty all its own; where M35 is a bright and widely scattered, NGC 2158 shimmers faintly; M35 is loud, whereas NGC 2158 is a quiet interlude.  Much of the difference is due to distance.  NGC 2158 is over five times farther away, nearly 16,000 light years.  It is also ten times older.

In my 18" at 100x NGC 2158 looked very much like a faint, unresolved globular with a smattering of brighter stars strewn over it.  At 425x the faint stars became resolved and the shape appeared too irregular to be a globular, taking on the appearance of an arrow head.