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NGC 6572. The Blue Racquetball "Stunning royal blue!"

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#1 iainp

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Posted 16 May 2018 - 12:03 PM

I'm used to seeing colour in planetary nebulae through the 20" Dob but nothing prepared me for The Blue Racquetball, NGC 6572, in Ophiuchus. It's small but bright and at 300X the colour was breathtaking, easily the most vivid colour I've ever seen in a DSO.  As you can see from the original notes below, it appeared as a stunning royal blue. even at 600X it was still full of colour. 

Its size, 0.3' x 0.2' and magnitude of 8.1v gives it a  Mean Surface Brightness of around 13.6 Mag/arcsec2, which, I read online, means it has a surface brightness 100 times that of the Ring Nebula!

It took 900X well but 600X gave the best views.  Due to seeing, I suspect, the central star wasn't visible, but at 600X the brightening along the west side (left in the sketch) was very apparent, as was the "sawtooth" detail along the south edge (at the bottom in the sketch). The central granulation  is a result of sketching artifacts not an observed feature, but the rest is "real" including the fainter halo around the main body. The OIII filter added nothing to the view.  The sketch is a combination of detail visible at 600X with a little at 900X and the colour at 100X and 300X.  

Iain 

Attached Thumbnails

  • NGC 6572w.JPG
  • IMG_3047.JPG
  • IMG_3048.JPG

Edited by iainp, 16 May 2018 - 12:06 PM.

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#2 niteskystargazer

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Posted 16 May 2018 - 03:49 PM

Iain,

 

Fine sketch of NGC 6572. (The Blue Racquetball "Stunning royal blue!") smile.gif .

 

CS,KLU,

 

thanx.gif ,

 

Tom



#3 tommy10

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Posted 16 May 2018 - 05:13 PM

Very cool sketch of dso that I can’t see, thanks for sharing.



#4 Aquarellia

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Posted 16 May 2018 - 11:42 PM

Bravo

Another nice target for me, thanks for sharing this,

What a Dob!

Michel



#5 Asbytec

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Posted 17 May 2018 - 06:19 AM

bow.gif

 

(I'm not speaking to you, only emoticons.)


Edited by Asbytec, 17 May 2018 - 06:24 AM.

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#6 iainp

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Posted 17 May 2018 - 07:10 AM

Ditto! waytogo.gif


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#7 azure1961p

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Posted 17 May 2018 - 10:00 AM

I recall this one with my C6, though no blue what so ever. Instead a bright uniform sphere of gas.  Still quite nice though. I like the contrasts you got witgin the face itself. Not at all an easy feat.  For all my efforts with the 150mm it  took highpower... I forget, something like 300x-400x to get an elongated shape otherwise it was this sphere at lower powers.

 

I'd be interested to see if you can get the red tint in the gas surrounding Campbell's Hydrogen Star.  It's in Cygnus.  Mag 9.5~ or so.

 

Pete


Edited by azure1961p, 17 May 2018 - 10:10 AM.


#8 iainp

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Posted 17 May 2018 - 11:17 AM

"I'd be interested to see if you can get the red tint in the gas surrounding Campbell's Hydrogen Star" Funnily enough Pete, I'm preparing my report on it right now wink.gif !


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#9 Warmvet

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Posted 17 May 2018 - 10:33 PM

Woohoo thats a beauty! I like the color of the PN and the background, very dramatic. To see that in a 20”...dreaming

 

Cindy



#10 iainp

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Posted 18 May 2018 - 01:47 AM

Thanks Cindy. Yes, the colour really was breathtaking, especially at lower magnification. It was intensely saturated at 100x: deep vibrant blue with a hint of purple.



#11 azure1961p

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Posted 19 May 2018 - 11:11 AM

"I'd be interested to see if you can get the red tint in the gas surrounding Campbell's Hydrogen Star" Funnily enough Pete, I'm preparing my report on it right now wink.gif !

 

That's cool it worked out this way. I've read so many things on this object. Overtime its been called a proto planetary, a carbon star and so forth.  It IS an oddity eh? And the real welcome thing of it all is the easy location and the brightness!

 

Attached youll see my C6 view of this nebula 6572.  It took a lot of power to just detect an elongation. Lower power, no way.  A nice vivid planetary and you got the Ming Dynasty Blue wink.gif

 

Pete

Attached Thumbnails

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#12 iainp

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Posted 20 May 2018 - 01:28 AM

Great sketch Pete.  I'm hoping for a steady night some time to really catch more detail in this one.


Edited by iainp, 20 May 2018 - 01:29 AM.


#13 Raul Leon

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Posted 25 May 2018 - 07:27 PM

It's funny how different eyes see different things. This has always been one of my favorite planetary nebula, I agree it is stunning, and the lower the magnification the more intense the color tends to be, but I have always seen this object as turquoise or intense emerald green. Maybe it has to do with aperture?  Raul



#14 iainp

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Posted 26 May 2018 - 01:27 AM

Raul, " I have always seen this object as turquoise or intense emerald green. Maybe it has to do with aperture?"

 

Yes, interesting,  I have wondered about that too.  Quite a few of these described as blue/green or turquoise appear blue to me, and not just a little blue but really blue! In fact, thinking about it, all the bright ones do.

 

Here's the Eskimo Nebula posted last month. I saw it as emerald green / turquoise with the 16" but just blue with the 20". The 20" gathers around 60% more light so maybe that's a factor, though the effect seems to be there whatever magnification used. 

Iain

 

Attached Thumbnails

  • post-226998-0-08049400-1520518945.jpg

Edited by iainp, 26 May 2018 - 01:28 AM.

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#15 frank5817

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Posted 28 May 2018 - 12:44 AM

Iain,

 

You and Pete report this one as blue and so do I but with a little bit of sky brightening this one becomes gray to my eye. I don't see green with this one.

 

Very nice.

 

Frank :)



#16 iainp

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Posted 03 June 2018 - 05:24 PM

Thanks Frank, I missed your comment before, for some reason. I'm looking forward to revisiting some of these PNs to see if there's variation between observations on different occasions.



#17 Randolph Jay

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Posted 04 June 2018 - 02:14 PM

I love this thread!  Such superb work Iain, Pete...and Pete I love your description of the color as "Ming dynasty blue"!!!  If I can make it to the desert next week I must take a look at this one against a dark sky.

Regards,

Randolph



#18 iainp

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Posted 04 June 2018 - 05:10 PM

Thanks Randolph, look forward to hearing / seeing what colour you report too!

Iain 



#19 azure1961p

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Posted 05 June 2018 - 10:44 AM

It's funny how different eyes see different things. This has always been one of my favorite planetary nebula, I agree it is stunning, and the lower the magnification the more intense the color tends to be, but I have always seen this object as turquoise or intense emerald green. Maybe it has to do with aperture?  Raul

One thing besides aperture that I found GREATLY affects color perception in dim objects is your dark adaption. By my condo where my drawing was made with the C6 I never really got true dark adaption. I cup my eyes, I do my best to avoid extraneous glare from neighboring lights but I NEVER get the reall deal.  It may very well be under a mag 6 country sky I couldve nailed the blue green color .  I  know NGC3242 at 50x exhibits an uncanny queer grey turquise with full dark adaption.  Its uncanny to scan this jewel into the fov. Something even as bright as Neptune with my 8" at the condo is grey with a touch of slate blue. Barely color at all. Under a mag 6 sky or even 5.5 with a full hours dark adaption its surprisingly colored a blue with hints of green.   Its no contest, the full dark adapted eye sees way more.  I try to defeat the condos ambient glare but it's no use. You can't cup your eyes THAT good and the sky is never that dark in town.

 

Just some thoughts.

 

Pete



#20 iainp

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Posted 12 June 2018 - 05:28 AM

Interesting about dark adaptation and colour perception Pete. I'm going to experiment some more with this next time there's a clear night, comparing impressions as I become more dark adapted, though in my garden you can always see your hand in front of your face very clearly, so I'll never get true adaptation until and unless I venture into darker skies and away from neighbours.



#21 azure1961p

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Posted 12 June 2018 - 09:03 AM

I'm curious Iain and this is off topic, BUT...

 

Have you ever considered going for Einstein's Cross? With your skills and aperture AND technique...

 

You know what Dude? You just might pull it off. Firsthand observation of a gravitational lensing mirage. Wow.

 

Pete



#22 iainp

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Posted 13 June 2018 - 04:11 PM

Thanks Pete, Einstein's Cross is on my To Do list but I got nothing when looking for the Twin Quasar, which I believe is supposed to be easier! The Twin appears as a 16 magnitude point of light or two 17 mag points depending on conditions, telescope and magnification, but it was invisible to me the 3 times I tried, though a 20" scope is supposed to be enough to find and split it. Another night...

Iain



#23 quazy4quasars

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Posted 21 January 2020 - 11:57 PM

Thanks Pete, Einstein's Cross is on my To Do list but I got nothing when looking for the Twin Quasar, which I believe is supposed to be easier! The Twin appears as a 16 magnitude point of light or two 17 mag points depending on conditions, telescope and magnification, but it was invisible to me the 3 times I tried, though a 20" scope is supposed to be enough to find and split it. Another night...

Iain

I've been able to resolve QSO B0957+561 in 17.5  from dark sites in Ca,  under very good conditions  I have also struggled with it in 25" under poor seeing conditions.  Great seeing should get you there.  You want to use high magnifications which will also darken the background sky.   You should also try for the "non-stellar" Andromeda's Parachute.... Don't go nuts if you fail these under bad-average  seeing conditions... Conditions will change.  



#24 Dave Mitsky

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Posted 22 January 2020 - 01:18 PM

The fact that NGC 6572 has the nicknames of the Emerald Nebula, the Blue Racquetball, and the Turquoise Orb is a good indication of the variability of color perception in this object. 



#25 Rick Runcie

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Posted 23 January 2020 - 06:28 PM

It's been my experience that people either see more green or more blue based on their respective eye sight. One evening approximately 10 years ago an extremely large Fireball the size of the full moon streaked across the sky over the New Jersey Pine Barrens as I was showing a friend and his future wife objects through my telescope for their first time. I saw the head of the fireball as turquoise leaning towards green my friend saw it as a vivid blue.


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