Jump to content


- - - - -

What's Up - M 35 and NGC 2158

Discuss this article in our forums

What’s Up

M 35 and NGC 2158

By Steve Coe

I am glad to see that you are still with me after all these years and all these articles.  So far I have been making my way around the sky one constellation at a time and we have covered lots of fun deep sky objects.  I do hope you have taken the time to go out and observe at least a few of them.

Now, for something completely different.  What I am going to begin with this article is to take on the sky one field of view at a time.  These articles will provide lots of information and observations about a few, or even just one, deep sky object at a time.  Do provide me some feedback either in the forum or as a private message.  The starting point for this new set of articles is M 35 in Gemini, I will include the open cluster NGC 2158.

M 35 is an open cluster near the feet of Gemini.  It is located half a degree west of the star 5 Geminorum.  This beautiful cluster contains 120 stars brighter than 13th magnitude.  M 35 contains several yellow and orange giants of late G and early K type. 

Robert Trumpler derived a distance of 840 parsecs or about 2700 light years.  More modern distances are not far different from Trumpler’s.  Lord Rosse counted 300 stars within a 13' radius.  Lassel in a 24-in called this cluster a marvelously striking object, the field of view is full of brilliant stars, unusually equal and even in distribution over the whole area. 

Walter Scott Houston spoke of this as his favorite open cluster and mentioned that it was visible with the naked eye under good skies.  The Webb Society Handbook on open clusters speaks of a starless region at the center of the cluster.  This dark central area is also the starting point for a chain of 9 stars that ends at the NE edge of the M 35.  At the end of that star chain is the wide double star ADS 4744.  The ADS designation stand for Aitken Double Star catalog.  It is composed of a 7th and 9th magnitude pair that is separated by 31 arcseconds.

Using 10X50 binoculars on a good night far from the lights of Phoenix M 35 is bright and large.  This cluster is very well detached from the Milky Way glow.  There are 6 stars resolved with direct vision and another 12 or so show up with averted vision.  Averted vision also makes the glow of this cluster larger.  The cluster includes a light orange star that is bright and stands out within the cluster.  NGC 2158 is easy on this night. 

In a TV 102 refractor and a 14mm eyepiece, M 35 is very bright, very large, rich and pretty compressed.  I counted 68 members with a beautiful chain that ends in an orange and blue pair.  The dark region within the center of this cluster is quite prominent in the 4 inch refractor.  NGC 2158 is 14mm pretty bright, pretty small and is much compressed in a triangular shape.  I can only resolve 2 stars in the 4 inch at this power but the cluster is pretty well detached from the Milky Way glow.  Going to a 6.7mm eyepiece shows 4 stars resolved with direct vision.  Using averted vision at this higher power shows 5 more stars resolved and a reveals a mottled background.

Observing with a 6" f/6 Maksutov-Newtonian on a night I rated the seeing at 6 out of 10 and the transparency at 8 out of 10 really shows off this excellent cluster.  Using a 35mm Panoptic shows M 35 as very bright, very large, somewhat compressed and rich in stars.  I counted 40 stars resolved, some lovely chains.  The 14mm eyepiece gives the best view.  I rated the cluster as very bright, large, rich and pretty compressed at this power.  86 stars were counted.  This cluster is well detached and contains a beautiful chain of stars that ends in a blue and yellow pair.  There is a dark triangular center and there are four stars involved that display a beautiful yellow color and the famous orange member near the center is easy. 

In a 13" f/5.6 Newtonian from a somewhat light polluted site, M 35 is bright, large, little compressed and very rich at 60X using my old 38mm Giant Erfle eyepiece.  There is a lovely orange star near the center of the cluster.  At 135X the cluster fills the field of view and I count 105 members on a fair night.  This cluster is just seen naked eye from my best observing locations in the mountains of central Arizona.  Lord Rosse counted 300 stars in this cluster, I will check that out when I get my 72" working.

NGC 2158, also in the 13" f/5.6, is pretty bright, pretty small, very compressed, and just barely resolved at 100X, going to 165X brings out a dozen stars.  I have seen this cluster with a wedge or arrowhead shape on a variety of nights using many different apertures. 

NGC 2158 in David Healy’s 32" f/7 RC is a “Wow” view indeed.  I counted 28 stars in a much compressed triangular shape.  There are several very close pairs and averted vision really makes it grow in size.

M 35+NGC 2158  MN 6” 65X           NGC 2158  16 inch  280X

M 35 and Mars   200mm lens at f/5  3 min exposure
NGC 2158 is below and to the left of M 35


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics