Galactic Cirrus around Messier 13

[Uwe Glahn]

Last new mood I tried the Galactic Cirrus around Messier 13, after seeing and reading the results of Mel.

With the 6" refractor which gave me a field of around 4° (f/5 + 30mm 3" eyepiece) and very good transparency of an High Alps location I could detect a nearly closed ring around the glob.

What makes me wonder is the missing of any deep image of M 13 which shows these brightening. Even a stretched DSS image shows no hints of any nebula.

So beside Mel's results which seems similar, are there any other sketches or descriptions of these nebula? I read that Mal shows these nebulas at the OSP, but what were the results?

sketch: 6", 25x, NELM 7m0+
M13.jpg
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[j.gardavsky]

The "M13 Arc" became visible through my 10x70 Nikon Astroluxe, and through my 15x85 BA8, five observings in total. Helpful have been the blue(RGB)CCD filters.

Also pretty spectacular is a network of the molecular clouds from Hercules into Draco, all relatively easy through the binoculars.

Clear skies,
Jiri

[MelBartels]

I showed the M13 IFN/galactic cirrus to many at the Oregon Star Party with my 30"F2.7. It's a great view - the cluster (with star colors), the galaxy, the fainter galaxy, IFN... All observers saw the IFN easily. In a big scope these IFN are bright - almost like Andromeda Galaxy in a small scope in bad skies. And yes, depending on visibility, in the darkest skies, they form a horseshoe around M13 with brighter/fainter sections. Mel Bartels

[Robin]

Nice sketch, Uwe! If this is a molecular cloud, shouldn't it show up on far infrared images, such as those shown with this Galactic Dust Map tool (down for maintenance on September 12)?: https://irsa.ipac.caltech.edu/applications/DUST/

You can enter coordinates or object names and radii around those and it will display extinction maps and 100 µm wavelength maps. For example, for 6 degrees around Messier 82 it shows what we know as Volcano Nebula.
For 2 degrees around Messier 13, in fact it shows a donut-like structure. I don't know if it coincides with your visual observations?

Clear skies

Robin

[Uwe Glahn]

Thanks Jiri, Mel and Robin,

Mel, thanks for confirming the structure. Of course I did not use any big aperture you mentioned. I have to revisit with the 27".

Robin, I downloaded the Galactic Dust Map. It is very rough and difficult to interpret, but it seems like it is a dark hole exactly on the M 13 position and some fainter dusk structures around this hole. Difficult to interpret, but especially at the NW and SE side there are some structures. Not to prove my seen nebula but perhaps a positive sign.

[MelBartels]

An imager just sent me a note with his deep image of the M13 clouds.

https://www.astrobin.com/xgxp1s/

It lines up really well with our visual sketches.

Mel