Coronet Cluster

[Akarsh Simha]

A few weeks ago, I came across the Coronet Cluster, an OB association in NGC 6729, apparently at the tip of the cometary nebula in the region (I found the designation Ced 165c for it on SIMBAD).

I tried to see if I could see any of it with my 28-inch this past weekend. Of course, Corona Australis is mighty low from California and the airmass is so high stars were very blurry even in moderate powers.

I was hoping to see something nevertheless, but all I saw was a bright point of light at the tip of the cometary nebula, a crescent shaped brighter rim to its edge, and a detached "knot" from the bright tip, a bit further southeast from the tip.

Has anyone tried to visually observe this cluster? Is it fully obscured in the optical band and therefore only visible in infrared? What's the deal with it?

Regards

Akarsh

[Mel Bartels]

I've seen NGC 6723, the globular nearby (nice resolved symmetrical) and the nebulosity but didn't note NGC 6729 explicitly. This with a 6".

Mel

[Akarsh Simha]

Hey Mel

Your sketched nebulosity matches well with the general region of nebulosity that runs through the region including NGC 6729. That must be really low from Oregon Star Party.

Regards

Akarsh

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[Victor van Wulfen]

Where the hell did that "flux" in your doodle to the northeast of the globular come from and how did you manage to miss searingly bright NGC6726/27, along with NGC6729 and IC4812?

Op 31 jul 2025, om 00:41 heeft Mel Bartels <melvin...@gmail.com> het volgende geschreven:

I've seen NGC 6723, the globular nearby (nice resolved symmetrical) and the nebulosity but didn't note NGC 6729 explicitly. This with a 6".

<image.png>

Mel

[Victor van Wulfen]

It doesn't. Not even remotely.

Op 31 jul 2025, om 00:55 heeft Akarsh Simha <akars...@gmail.com> het volgende geschreven:

Hey Mel

Your sketched nebulosity matches well with the general region of nebulosity that runs through the region including NGC 6729. That must be really low from Oregon Star Party.

Regards

Akarsh

On Wed, Jul 30, 2025 at 3:41 PM Mel Bartels <melvin...@gmail.com> wrote:

I've seen NGC 6723, the globular nearby (nice resolved symmetrical) and the nebulosity but didn't note NGC 6729 explicitly. This with a 6".

<image.png>

Mel

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[Akarsh Simha]

Here's my understanding, Victor. If you look at the DSS2 of the region, there is a band of dark nebula with a band of dim reflection nebulosity on either side running through the region marked in Mel's sketch. The observation was clearly made at very low power where the condensed glow of NGC 6729 would meld into the star. Our eye is more sensitive to contrast than the brightness of the objects and I could see a case for the taper of the fuzz of NGC 6729 melding into the rest of the nebulosity. The cometary nebula I am talking about, at this low power, is marked as a small blip. I can see an argument for the mismatch between the DSS2 and the sketch being an artifact of using low power.

I on the other hand was running about 291x and clearly saw the glow of NGC 6729 but none of the dimmer streams of nebulosity (also did not have the contrast down to the horizons for it anyway). 

My nitpick is that I would not call it "IFN" at such a low galactic latitude, and just call it galactic nebulosity. Terminology of what light is illuminating the ISM.

Regards

Akarsh

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[Mel Bartels]

Having a bad day, are we? Take the time to read my drawing (it's not a doodle - that's insulting and unnecessary. I spent a fair amount of time observing the field and I remember showing it to several other amateurs). 

I drew what I saw in the 6" f2.8 with 4.3 deg field at 23x (SQM 21.3) back in 2016. 

The image on the left is cropped from https://astronomiapampeana.com.ar/astrofotos/med/6727_med.jpg

As to why I didn't see this or see that, I can only say that I drew what I saw, nothing more and nothing less. 

Mel Bartels

[Steve Gottlieb]

Here’s the 1997 discovery paper on the Coronet Cluster in NGC 6729.  It’s not an OB association but a cluster of ~10 YSOs (pre-main-sequence stars) discovered using deep infrared imaging. Most of the members “illuminate” small infrared reflection nebulae.  I would doubt that it’s visible in the optical.  The bright erratic variable R CrA is at the NW end (also pre-main-sequence) and fainter T CrA at the SE end.  I found the large dark nebula, Bernes 157, to the SE of NGC 6729 just amazing from Australia.

Steve

P.S. Ced 165c refers to the NGC 6729 reflection nebula itself, not the infrared cluster.

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[Scott Harrington]

As your friend, Victor, I must say that I'm disappointed by the unkind manner in which you phrased your question to Mel.

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[Jay inUT]

Mel 

Well done I say. You captured what you saw which in my opinion is what we should do when we sketch at the eyepiece. 

It is a shame that in today’s world asking a question is more “snarky” than phrasing it in such a way that the person asked can explain. Sometimes I fear in today’s world it is more about being right. Far better is the motto “seek first to understand, then be understood.” Hopefully this doesn’t continue. 

Jay

Sent from my iPhone

On Aug 2, 2025, at 9:05 AM, Scott Harrington <sn4...@gmail.com> wrote:



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[Akarsh Simha]

Hi folks

As the list owner, I request that we please let us put an end to this discussion.

There are cultural norms around politeness (which I think Jay hinted at) which are different in different people’s minds. Both Victor and Mel are amongst the world’s most knowledgeable visual astronomers in their own right and they’ve contributed tremendously to our hobby. I consider it a privilege to have them on this list, just like I feel about many of you being here.

I hope we can look past this, and have everyone continue participating amicably.

Sincerely

Akarsh

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