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AX Cygni: A Carbon Gem!

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#1 David Gray

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Posted 04 June 2017 - 03:31 PM

Thought I would post the sketch from this post-midnight view of a striking carbon star.  I feel that my doubly afflicted sky (Moon & northern twilight) which takes on a deep indigo when it is haze-free tends to set off carbons' tints quite nicely – so its good to get a little something positive at this time of natural light pollution and DSO withdrawal.........


There is a degree of admission/self-chastisement with this........I pride myself on finding objects pretty quickly, all other things equal; but a few nights back was an abject failure to locate it.


Looking for carbon stars on Sky Map Pro 12 I had mentally booked this for a looksee, so on May 26/27 the debacle commenced and a soon light sky had me giving up. 


Out observing I’m in the zone: laid back, self-assured and pretty much unflappable unless something like those guys ‘lamping’ hares with high-powered torches in the adjacent field turn up.  Out of sight of me at the scope but the inside of the back of the observatory gets to look as though there is a lightning storm going on – when I feel like shouting “No hares in here........**!!**!!”..... but best not to antagonize with an exposed scope.............!  No hare-hunters of late but that’s the measure of how rattled I was with the AX Cygni failure.


Last night/morn found it in minutes..........crazy.gif .........and quite a gem.  I had not caught, in SM Pro, what is apparently another fainter Carbon star – fainter than AX but nicely contrasting with a blue star (these at field-top).  My initial intrigue was the blue coarse triple (STT 391) which I had anticipated to give a contrast with AX but alas rather too far apart – maybe better for those equipped with a 12”-18” at <100x to get the effect.  I can get 110x with a 60m Kellner; so just maybe when darker skies return.  But ironically the fainter two at field-top were more effective...........


The wide double near the left field-edge is STT 393; and there is also a strongly orange star: the uppermost of the two above-left of AX.  Maybe two and a ‘half’ carbon stars in one field......tongue2.gif


Looking at AAVSO AX Cyg is shown on a fade to below 8.0 but looked nearer to 7.5 to me – I know I am red-sensitive........but that much........shocked.gif




AX Cygni.jpg

Edited by David Gray, 04 June 2017 - 03:36 PM.

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#2 Randolph Jay

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Posted 04 June 2017 - 03:45 PM

Beautiful, exquisite!  I must get a sight of this one. I love ( though I'd hate them too ) your "hare" raising  story.  Ah not a problem in my suburban backyard...just an occasional large racoon ( and they don't yet carry torches of any kind, but that day may be coming :))  Seriously now, I love that sketch and that color.  Next clear night ( maybe Thursday ) and even with the moon around, I must try to see this one.

Regards, clear ( and hare free hunter ) skies!


#3 Sasa



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Posted 04 June 2017 - 03:48 PM

Great sketch with quite dramatic colors!


I pay attention to star colors during star-hopping. I just make small remark in my logbook and later at home, I'm trying to find out more about the stars. Many times, this is an interesting star (variable star, red giant, etc...). Last time, when I run on carbon star, it was at the end of March while searching for comet Tuttle-Giacobini-Kresak with my 82mm refractor. The comet was at the Draco's tail. I cruise rarely in this region. In fact, I run on several pleasant surprises in there. The first one was star 10 Dra close to Alpha Draconis. It had strongly golden hue (at home I have found out this was variable red giant M3.5III known as CU Dra). Second nice field had 4 brighter stars (kappa, 4 Dra, 6 Dra ad BD+70 707) with nice color contrast (4 Dra and 6 Dra were orange, while kappa Dra was bluish, the last star was yellowish). And the third surprise was nice bright pair 8 Dra and carbon star RY Dra. While 8 Dra was crystal white, RY was strongly red.

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#4 PeterDob


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Posted 05 June 2017 - 04:20 AM

What an exquisite FOV! Beautiful sketch, David! bow.gifbow.gifbow.gif





#5 frank5817


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Posted 06 June 2017 - 11:35 AM



Carbon stars are wonderful to look at on any good night. I tend to incorrectly estimate the brightness by a few tenths of visual magnitude because of the well known Purkinje effect.

Excellent sketch.


Frank :)

#6 niteskystargazer


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Posted 06 June 2017 - 01:21 PM



Very nice sketch of AX Cygni: (A Carbon Gem!) smile.gif .




thanx.gif ,



#7 flt158



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Posted 06 June 2017 - 02:10 PM

Hi David Gray. 

That is a very interesting star field alright. 

I did observe AX Cygni way back in 2003. 

Perhaps I should revisit it again soon. 

It is after all very near one of my favourite double star -Delta Cygni (Rukh). 

There surely are quite a few orange stars nearby. 


Thank you for your excellent sketch. 



#8 David Gray

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Posted 06 June 2017 - 03:23 PM

Thanks Randolph, Sasa, Peter, Frank, Tom, Aubrey and the Likes Appreciated.......smile.gif


My blighted summer-bright (+ moonlit at times!) skies are proving productive for this kind of inquiry it seems......


Frank: I had considered the Purkinje Effect; but maybe a bit less simple in that I suspect the indigo hued sky might have been a factor.  My judged mag. 7.5 was not really a ‘formal’ estimate as I had not chosen a ‘similar’ comparison to make one. 


Staring makes the effect worse I find and that is also something I avoid with colour impression seeking in particular. Rather I spend around a second to look at one star then shifting to another in the field and back and forth and etc. I find a sustained look tends to leach out the colour – especially working with near-scotopic vision; and further feel that the vision works best with the relative-colour effects/impressions of quick inter-comparison.  This allows me to get relatively delicate hues to near mag. 13.0 with the 16.3" D-K on good (dark) nights and in presumably close to being scotopic.


I feel that given the prevailing summer & moon lightness the sky was having me well into the photopic/mesopic zone of my vision......



Edited by David Gray, 06 June 2017 - 03:32 PM.

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#9 Special Ed

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Posted 07 June 2017 - 08:01 PM



Beautiful starfield--nice to look at your sketch.  I can only see the most obvious colors in stars.  You have a talented (and trained) eye.

#10 azure1961p


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Posted 07 June 2017 - 09:18 PM

Beautifully done David!


You nailed that rusty tone a lot of redder stars have.



#11 stevecoe


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Posted 07 June 2017 - 09:45 PM

Excellent drawing, good color.  I agree with the "burnt orange" color that so many of these stars present to my eye.


Here is my observation:


AX Cyg
Nexstar 8 133X medium orange, Good Color.  In a rich field around this carbon star.


Steve Coe

#12 David Gray

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Posted 13 June 2017 - 04:16 PM

Many Thanks Michael, Pete, Steve.


I’ve thought for some time that there are two basic ‘themes’ to the hues of these stars: where I might put some in a slight yellow-toned hue and the other where there is a distinct polished-copper tone underlying. Of course not possible to compare them side by side and all sorts of factors cloud the issue..........conditions, physiological, optical etc. etc.


Two of my favourites V Aql & VX And often seem in that polished copper region to me.  Got a quick look at V Aql on the 9th and was musing that when it comes to tinting in Corel it might need a slight addition of magenta to the reds/oranges I apply to match my impressions.  Y Cvn (La Superba) and X Sge I put in the yellower category.


Two pretty well known ones I have never viewed are T Lyr & S Cep – need to address that soon........blush.gif



Edited by David Gray, 13 June 2017 - 04:18 PM.

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