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M15: The Great Pegasus Cluster

DSO Observing Report Sketching
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#1 bphaneuf

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Posted 14 August 2022 - 06:24 PM

M15 has one of the greatest fall-offs in brightness moving outward from the core.  Especially given its distance of over 33k ly, that gives its center an almost stellar appearance.  In fact, that belies its Shapley-Sawyer classification of IV.  A very large percentage of its over 100,000 stars are in the central, collapsed core region, so visually M15 looks like it should be a Class II.  Apparently, classifying GCs is not as straightforward as how they look.  All that aside, M15 looked gorgeous.  Even under the light of a 94% illuminated moon.  What am I doing observing DSOs under a nearly full moon, you ask?  The word, I think, is desperate.  At least clusters hold up better than most other types of DSO.

 

Observation:  Transparency appeared to be good, but not great.  And seeing was in the tank.  Saturn looked like it was underwater, making the rings and Cassini division only occasionally resolved.  The moon was casting shadows, and no doubt robbing significant detail from this still spectacular object.  My first impression was one of a frozen explosion.  The center was still incredibly bright – not quite stellar, and very distinct from the surrounding halo.  A poster child for core-collapsed globulars.  The core was so small and bright it was impossible to make out individual stars inside it, although many were resolved just outside that brilliant spot.  Many of those stars made up small chains near the core to the outer edges of the halo.  Given how small the core is, the halo appeared unusually extended, and very symmetrical.  Many, many barely resolved stars were discerned in the halo, giving it a granular appearance.  Even under the poor viewing conditions this one is an attention-getter.  The star field was a perfect backdrop, with three particularly bright stars framing the glob in a flattened triangle.  It might have been richer with stars with less moon.  I fully intend to revisit this one under better conditions and post the comparison/contrast.  That way, at least, a sub-par image will one day serve a purpose.

 

Sketching:  White pastel pencils and powder on Hamilco 80lb black card stock.  Used a larger round brush rather than one of the mops, since the smallest I have is 1” or #8.  That’s going to change soon!  As I’ve mentioned before, I dump excess powder rather than blow it, but learned a lesson doing that this time.  I allowed the paper to hit the edge of the trashcan and didn’t notice the scrape marks until I took the photo of the sketch.  Could not find a way to eliminate them.  My smallest stipple brush with a heavy load made up the core, and an empty brush blended it ever so slightly into the halo.  Later went back and enhanced the center with the soft pencil as the stars near the core appeared to outshine it.  The smallest stipple brush empty was used to soften the edges.  The halo itself was swirled with an empty brush to even it out.  Even used a large blending stump that helped more than I thought it would.  A continually sharpened soft pencil placed the brightest stars in the field and in the cluster itself.  Medium and hard were used for the others, depending on apparent magnitude.   Both medium and hard pencils were used to shotgun the halo and just outside it.  The triangle of brightest field stars got a dot from the gel pen.

 

M15.jpg

 

Clear skies and dry paper!

-b


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#2 frank5817

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Posted 14 August 2022 - 06:55 PM

Butch, Very nice sketch here of M-15. Your description of how you did this sketch is very good. It would have been even better under good seeing,so you will need to go back and do it again in the future. I have a feeling you will like doing that. :).

When conditions are just right go after planetary nebula Pease 1. You will likely find it easily.

 

Very nice post.

 

Frank :)


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#3 bphaneuf

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Posted 14 August 2022 - 07:04 PM

Butch, Very nice sketch here of M-15. Your description of how you did this sketch is very good. It would have been even better under good seeing,so you will need to go back and do it again in the future. I have a feeling you will like doing that. smile.gif.

When conditions are just right go after planetary nebula Pease 1. You will likely find it easily.

 

Very nice post.

 

Frank smile.gif

Thanks Frank!  Those are indeed the plans, including Pease 1!  I'm hoping to post a side-by-side comparison when that day comes. 

-b
 


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#4 TienTran@134

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Posted 14 August 2022 - 09:40 PM

M15 has one of the greatest fall-offs in brightness moving outward from the core.  Especially given its distance of over 33k ly, that gives its center an almost stellar appearance.  In fact, that belies its Shapley-Sawyer classification of IV.  A very large percentage of its over 100,000 stars are in the central, collapsed core region, so visually M15 looks like it should be a Class II.  Apparently, classifying GCs is not as straightforward as how they look.  All that aside, M15 looked gorgeous.  Even under the light of a 94% illuminated moon.  What am I doing observing DSOs under a nearly full moon, you ask?  The word, I think, is desperate.  At least clusters hold up better than most other types of DSO.

 

Observation:  Transparency appeared to be good, but not great.  And seeing was in the tank.  Saturn looked like it was underwater, making the rings and Cassini division only occasionally resolved.  The moon was casting shadows, and no doubt robbing significant detail from this still spectacular object.  My first impression was one of a frozen explosion.  The center was still incredibly bright – not quite stellar, and very distinct from the surrounding halo.  A poster child for core-collapsed globulars.  The core was so small and bright it was impossible to make out individual stars inside it, although many were resolved just outside that brilliant spot.  Many of those stars made up small chains near the core to the outer edges of the halo.  Given how small the core is, the halo appeared unusually extended, and very symmetrical.  Many, many barely resolved stars were discerned in the halo, giving it a granular appearance.  Even under the poor viewing conditions this one is an attention-getter.  The star field was a perfect backdrop, with three particularly bright stars framing the glob in a flattened triangle.  It might have been richer with stars with less moon.  I fully intend to revisit this one under better conditions and post the comparison/contrast.  That way, at least, a sub-par image will one day serve a purpose.

 

Sketching:  White pastel pencils and powder on Hamilco 80lb black card stock.  Used a larger round brush rather than one of the mops, since the smallest I have is 1” or #8.  That’s going to change soon!  As I’ve mentioned before, I dump excess powder rather than blow it, but learned a lesson doing that this time.  I allowed the paper to hit the edge of the trashcan and didn’t notice the scrape marks until I took the photo of the sketch.  Could not find a way to eliminate them.  My smallest stipple brush with a heavy load made up the core, and an empty brush blended it ever so slightly into the halo.  Later went back and enhanced the center with the soft pencil as the stars near the core appeared to outshine it.  The smallest stipple brush empty was used to soften the edges.  The halo itself was swirled with an empty brush to even it out.  Even used a large blending stump that helped more than I thought it would.  A continually sharpened soft pencil placed the brightest stars in the field and in the cluster itself.  Medium and hard were used for the others, depending on apparent magnitude.   Both medium and hard pencils were used to shotgun the halo and just outside it.  The triangle of brightest field stars got a dot from the gel pen.

 

attachicon.gifM15.jpg

 

Clear skies and dry paper!

-b

It's a good looking sketch, I love it !!! The last time I looked at this cluster I couldn't resolve any star of it. I sure gonna give this one a try again let see if I can resolve stars in the outskirt of this glob. Right now I have to deal with light pollution, clouds, and the Moon. Literally three of the worst enemies for DSOs observing lol.gif lol.gif lol.gif !!!


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#5 bphaneuf

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Posted 14 August 2022 - 09:50 PM

You've got one more problem than I do wink.gif


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#6 JMSchwartz

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Posted 14 August 2022 - 10:33 PM

B- this looks great it can only get better with darker skies although this is amazing that you could render this glob with such detail despite the stray moonlight . B- You have a very keen eye for  the  sharp details.

Awesome work. 

Cheers Jon


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#7 rodelaet

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Posted 15 August 2022 - 02:50 AM

Butch. Excellent sketch and a very good report. 
M15 is a very beautiful object. I’m always surprised of its elegant looks compared to the coarse appearance of M13. 


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#8 jlcop

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Posted 16 August 2022 - 08:38 AM

Very well-done sketch and commentary.
John
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#9 bphaneuf

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Posted 16 August 2022 - 08:54 AM

Butch. Excellent sketch and a very good report. 
M15 is a very beautiful object. I’m always surprised of its elegant looks compared to the coarse appearance of M13. 

That is a great contrast to note Rony.  You can see that to a lesser degree with M13 and M92 in the same neighborhood.  I'm thinking M15's halo appears much smoother than M13 because it has so many fewer stars in it, relatively speaking, as a large percentage have dropped into the central core region. 

-b
 



#10 niteskystargazer

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Posted 16 August 2022 - 11:00 AM

Butck,

 

Very good sketch of M-15: (The Great Pegasus Cluster) smile.gif .

 

CDS,KLU,

 

thanx.gif ,

 

Tom



#11 Achernar

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Posted 20 August 2022 - 10:23 AM

This is a really good sketch of M-15, which like other globular clusters can actually be difficult to sketch well due to the sheer numbers of stars they contain. It takes really bad skies to detract from the view when it comes to bright globular clusters such as M-15.

 

Taras


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#12 bphaneuf

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Posted 20 August 2022 - 11:47 AM

This is a really good sketch of M-15, which like other globular clusters can actually be difficult to sketch well due to the sheer numbers of stars they contain. It takes really bad skies to detract from the view when it comes to bright globular clusters such as M-15.

 

Taras

Thanks Taras.  Alas, that's why I went with globulars on the 13th.  Poor seeing and way too much moon, and nothing but clouds on other nights bawling.gif
 


Edited by bphaneuf, 20 August 2022 - 07:36 PM.



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