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How to observe the Cone Nebula?

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#1 hokkaido53

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Posted 12 October 2013 - 08:05 PM

I would like to know if it is possible to obtain a good visual observation of the Cone Nebula, which is part of NGC2264, the "Christmas Tree" cluster in Monoceros. The nebula looks spectacular in photos, but I have never been able to bag it visually. I live under dark skies and have an 18" reflector, but over the past two mornings, I haven't been able to see this elusive object.

How much magnification is needed? And is a filter necessary? If so, what kind?

Thanks in advance for any advice,

Roy in Taos

#2 GlennLeDrew

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Posted 12 October 2013 - 10:53 PM

You'll need a quite dark sky, and an H-beta--or at least a UHC--filter will help. This object is somewhat reddened by intervening dust, and so the visibly important emission near 500nm is more strongly attenuated than the deep red H-alpha. The result, as it is for many other such reddened nebulae, is a photographically obvious object which visually is very subtle.

At such low surface brightness and contrast, you may need to have the feature you desire to see subtend several degrees on the retina in order to detect it. Find out the Cone's width, then calculate the magnification required to bring it up to, oh, 5 degrees. If we take a width of 4 arcminutes, to subtend 5 degrees requires a magnification of 75X. If a narrow band filter is employed, the exit pupil should be at least 4mm, implying an aperture of at least 300mm (at 75X.)

#3 curiosidad

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Posted 13 October 2013 - 10:18 AM

And with binoculars, it´s possible?
Thanks

#4 David Knisely

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Posted 13 October 2013 - 12:45 PM

And with binoculars, it´s possible?
Thanks


No, it is somewhat small in scale and too faint to be seen in most binoculars (unless maybe you are using a pair of large Newtonian telescopes in some sort of "binocular" configuration). I have seen it (barely) in a 10 inch Newtonian on a superb night when using a narrow-band nebula filter (Lumicon UHC), but it was still pretty marginal. In my 14 inch Newtonian, I have seen it a few more times, but it still is more of a vague darkening of the sky background extending to the south from a faint pair of stars than anything else. In larger apertures, the H-beta filter may provide a bit more contrast than the narrow-band filters will, but the "cone" is still a very difficult target visually (notably harder to see than the Horsehead is). Clear skies to you.

#5 hokkaido53

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Posted 13 October 2013 - 03:35 PM

Thanks for the quick replies,

Roy

#6 Tony Flanders

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Posted 14 October 2013 - 05:31 AM

I would like to know if it is possible to obtain a good visual observation of the Cone Nebula, which is part of NGC2264, the "Christmas Tree" cluster in Monoceros.


I agree with others here that this is an extremely difficult object to observe. I have never obtained a view that really satisfied me.

For the record, the Cone is technically the dark indentation on the south side of the bright nebula. The bright nebula is huge, and seems almost hopeless to detect in its entirety since it is mixed with a rich Milky Way field on the northwest.

#7 HellsKitchen

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Posted 14 October 2013 - 05:57 AM

You need very dark skies. Use a magnification of about 70-120x (try experimenting to see what works best) and a H-beta or UHC filter. This is one of the hardest objects to observe, a very dark sky is crucial here. The Cone nebula is regarded as even harder than the Horsehead to observe. I've visually spotted the Horsehead in a 12" from my outer suburban backyard, but absolutely no hint of the Cone.

#8 Dave Mitsky

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Posted 14 October 2013 - 02:57 PM

My only glimpse, and a less than impressive one it was, of the Cone Nebula was in 2005 through a filtered 30" Tectron Dob at an altitude of 7,000 feet at New Mexico Skies.

Dave Mitsky






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