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M 13' s propeller - first time view


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It is strange, how the eye/brain team of a DSO's observer can be accustomed to view the faintest light structures on a dark sky background, and, in contrast to that, may have it's difficulties when it comes down to observe dark structures in brighter objects. When I went out this evening 20.00 CEST, the observing conditions were not great; NELM 5.0; SQM-L 20.6; together with a lot of light pollution (cars; two illuminated restaurants close by etc.), so I decided to point the 18" at M 13, without too much expectations. With 164x mag (Docter 12.5 mmf), several star lanes, known as "Herschel's hairs", mostly directed to N, were quite obvious. But up to now I have never been able to spot the dark lane structure known as the "propeller". This time, I spent, in analogy to some DSO sessions on faint objects, about 15 minutes to observe the cluster. Letting the eye wander again and again across the bright, widely resolved cluster, changing from direct to averted vision and back, slowly the dark "Y" pattern, resembling a "Mercedes" logo emerged in the S part of the cluster. One arm was pointing W, the two other ones to NNE and SE. The whole structure took up about 25% of the cluster's apparent diameter. I was not able to view it constantly - it "disappeared" several times, but returned, when I paused for a minute or had a look at the NGC 6207 galaxy close by. I guess, my brain will have stored the view now adequately, and it will be visible more readily the next time when I'm chasing it.

A nice, appropriate sketch by Michael Vlasov:

http://skyandtelescope.org/wp-content/uploads/Globular-M13-sketch-Michael-Vlasov.jpg

An article by Phil Harrison about the propeller:

https://www.cloudynights.com/articles/cat/column/phil-harrington-s/cosmic-challenge-m13s-propeller-r3106

 

Thanks for reading

 

Stephan

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It’s an interesting feature, certainly. I’ve seen it best in a C8 Edge I seem to recall, not really observed it with anything bigger but that would be great, hope to manage it soon.

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Nice report of an interesting feature :icon_biggrin:

The Propeller looks great with my 12 inch dob at 265x on a dark night.

Through my smaller aperture scopes it's not very distinctive at all.

 

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On 09/10/2021 at 15:29, Nyctimene said:

several star lanes, known as "Herschel's hairs", mostly directed to N, were quite obvious.

Years ago a member Qualia sketched M13 that showed some star trails- I see these trails and had discussed it with him way back. I was wondering if these "detached" star trails are "Herschels hairs"? Do you see M13 like this as well? These features really add beauty to the object.

 

 

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Edited by jetstream
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On 11/10/2021 at 14:15, jetstream said:

Years ago a member Qualia sketched M13 that showed some star trails- I see these trails and had discussed it with him way back. I was wondering if these "detached" star trails are "Herschels hairs"? Do you see M13 like this as well? These features really add beauty to the object.

I can make out the star trails/chains slightly "detached" quite well, but not as prominent as in Qualia's sketch. And, yes, these trails are "Herschel's hairs" - to quote his description (John Herschel, btw.): "hairy looking, curvilinear branches".

Stephan

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I’ve seen the propellor with my 12”; I think it’s a matter of seeing more than anything else. 
Ever since my son was a little boy, M13 has been his favorite object, so we’ve watched it A LOT 😅 

actually, the first view with the 18” was dedicated to M13. It was another sight! The whole cluster is riddled with dark lanes, and there were actually 2 ‘propellor’ like features. Give it another try next time ;) 

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23 minutes ago, John said:

Some nice galaxies near Messier 13 as well :icon_biggrin:

https://skyandtelescope.org/observing/m13-and-galaxies/

I've observed only 6207 (regularly when visiting M 13), but have never been able to spot IC 4617 up to now. Encouraging, that there are some "brighter" galaxies  close by; I'll give it a try, perhaps next year, when Hercules is high positioned again!

Stephan

 

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1 hour ago, Nyctimene said:

I can make out the star trails/chains slightly "detached" quite well, but not as prominent as in Qualia's sketch. And, yes, these trails are "Herschel's hairs" - to quote his description (John Herschel, btw.): "hairy looking, curvilinear branches".

Stephan

Thanks Stephan I always wondered what this feature was- I see them at least as good as the sketch but oddly enough they seem sensitive to aperture. The 10" and 15" do vg but the smaller scopes and the 24", no. The big scope drowns the features out, the smaller ones dont pull enough stars. When everything is right Herschels hairs are a truly great feature to see.

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3 minutes ago, Astro_Dad said:

Enjoyed your report @Nyctimene. What do you think- bit of a stretch with my 8 inch in a designated dark sky zone or could I scape it?!

I really don't know - never saw it with my 8". Please check Phil Harrington's article linked above; there have been observers who spotted the Propeller with 6" scopes. The designated Dark Sky zone might help a bit. High magnification is needed.

Give it a go, and let us know!

Stephan

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3 minutes ago, Nyctimene said:

I really don't know - never saw it with my 8". Please check Phil Harrington's article linked above; there have been observers who spotted the Propeller with 6" scopes. The designated Dark Sky zone might help a bit. High magnification is needed.

Give it a go, and let us know!

Stephan

Will do… as soon as those clear skies return! 

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