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Sketch of NGC 2420 an open cluster in Gemini

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#1 Starobserver


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Posted 14 August 2009 - 02:15 PM


Here's my sketch and observing report of NGC 2420 in Gemini, an open cluster in the neighbourhood of the Eskimo Nebula.

Sketch details
Date / Time : 27/12/08 / 00:34
Observing Location : Landgraaf, Netherlands
Seeing / Transparency : 3 / 5
Telescope : Orion Optics UK 300mm
Eye-piece :: 12mm Nagler Type 4
Magnification / Field of View ': 133 / 37

Observing report
With the 300mm Dobson and the 35mm Panoptic I see NGC 2420 as a smudge, so it's not an easy object, but on the other hand it isn't too difficult. Giving the tube a little nudge, makes the smudge stand out more clearly from the dark background. Increasing the magnification with the 12mm Nagler T4 to 133x, helps to resolve this small and compact cluster partially. With the 7mm Pentax it's resolved even more, but I like the view in the 12mm better, so that will be my optimum magnification for producing the sketch.

With direct vision I count about 20 stars, a relatively poor cluster. However with averted vision the number of stars increases rapidly, and becomes about 40 to 50 stars, so this would make it a moderately rich cluster. According to Hynes (Star clusters) there are about 300 stars in this cluster, but visually I don't see more than 50, whatever I try. There are no dark lanes visible and there is no central star or a star with a specific colour in NGC 2420. I do not detect any significant double or multiple stars.

To the south of the cluster, is a bright yellow-orange star visible. I don't know if it belongs to the cluster but I will put it in the sketch anyway. With averted vision I not only see more stars popping in and out of the field of view, but I also notice a glow of unresolved stars. I do not see any asterisms in the cluster, except for a group of 4 stars on the southern edge of the cluster that seem to form a kind if hook. NGC 2420 looks a little irregular with no real centre.

If you want a little more info on the discovery of this cluster, where you can find it, and it's position in our galaxy, please follow this link to :NGC 2420 at Starobserver.eu

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#2 JayinUT


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Posted 14 August 2009 - 06:36 PM


Excellent observation and sketch! I enjoy effects of the stars in the cluster in your sketch.

#3 rolandlinda3



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Posted 14 August 2009 - 10:30 PM

Very pleasing sketch.

#4 kraterkid


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Posted 14 August 2009 - 10:57 PM

Wonderful sketch and very interesting report Math! :waytogo: I liked hearing what judgements you made when considering how best to frame the view in terms of magnifications/eyepieces. What magnitude do you feel the other 250 stars in the cluster would have to be if you can't see them in your 12"? I'm not sure what the limiting magnitude is for your scope and sky.

#5 frank5817



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Posted 15 August 2009 - 01:42 AM


Your colorful sketch of this open cluster looks very nice.
Thanks for posting this little gem. :bow: :rainbow: :cool:

Frank :)

#6 Starobserver


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Posted 15 August 2009 - 01:42 AM

Hi Rich,

First a little about my limiting magnitude. I live in a suburban area, with a lot of light pollution. On top of that, I live in an area with severe ait pollution, one of the worst in my country. So once or twice in a year, I have such good conditions that I should be able to see right down to magnitude 14, but.......... the standard is magnitude 12 to 12.5 with the 300mm. So I guess a lot of stars in this cluster will be invisible for me most of the time.

When framing an object before sketching it, I first observe it with all my eyepieces, trying all different magnifications. This takes about 15 minutes. I use the data I gather during these 15 minutes for my observing report. In the end I pick the eyepiece/magnification that showed to object the way I liked it most, and thats it! I start to sketch using only one magnification. I never use higher magnifications that would probably get me more details, but the object would fill the whole field of view or would even be bigger than the field of view.I don't like that. I just like to sketch it in one go, so that it represents what I have seen at the telescope.

Hope this answers your questions.

#7 gufle


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Posted 17 August 2009 - 04:12 AM

Hi math,

Nicec sketch. I also liked the background you gave on your website of the object

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