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View Full Version : Object of the Week, July 14, 2019 – NGC 6207 - the famous companion of the Hercules cluster



Uwe Glahn
July 14th, 2019, 08:42 PM
NGC 6207 - the famous companion of the Hercules cluster

Constellation: Hercules
RA: 16h 43m 03.7s
DEC: +36° 49’ 55”
Mag: 11.4v
Surface Brightness: 12.6
Size: 3.0’ x 1.2’

"Often seen, never observed."

This was my experience with this famous galaxy 0,5° northeast of Messier 13 until I got a look through a 36-inch telescope which shows a large amount of detail even at a quick and dirty look.

With 11.4vmag even visible in the smallest scopes, we often go to (quick) the famous globular or the more difficult IC 4617 between the glob and NGC 6207.

William Herschel discovered this galaxy in 1787. Otherwise, little is known about this galaxy. No special catalog entry or no unusual physical features. But the spiral galaxy shows many brighter HII regions Zaragoza-Cardiel et al. [ZGO2015] cataloged and which are seen in the ALADIN viewer. Most unusual detail is a 14mag foreground star which is often confused as an SN.

Most interesting fact are the distance steps between the objects. Even trough the distances are not as accurate, the factor is roughly ok.
- NGC 6207 ~ 41 MLj
- foreground star within NGC 6207 ~ 3600 Lj
- M 13 ~ 25000 Lj
- IC 4617 ~ 510 MLj
In other words, NGC 6207 is around 10000x further away than the foreground star, or around 2000x further away that M 13. Isn't that fascinating?

Now that's your turn - can you see the foreground star?...can you see details like the brighter HII regions or the necking appearance?...

DSS blue plate, 30'x30'
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picture: Dietmar Hager, 9-inch Apo
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sketch: 27", 419x, Seeing III, NELM 7m0+
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Give it a go and let us know!

Ivan Maly
July 15th, 2019, 01:08 AM
Very nice sketch there, Uwe. This is one of my favorite galaxies. Here is an observation that I made three years ago with our club scope (20").

https://3.bp.blogspot.com/-8v_nPF9Z0XM/V27IzhHhfdI/AAAAAAAABzA/aKVZgVRHCuEJYBJtzBUXuWRvAHpqctn1wCLcB/s320/NGC%2B6207%2B2016-06-24%2B20in.jpg

The notes say: "June 24. BMO 20". Clear, warm, dry. Astronomical twilight 23:12, moonrise 23:48. SQM 21.29. 13, 8, 5.5 mm 100-deg for ~200, 300, and 450x. Mostly 300. Nucleus and S knot are likely due to superimposed stars. N up."

Dragan
July 17th, 2019, 04:42 PM
In regards to IC4617, it's amazing how many people have completely glossed over it. 4617 isn't a particularly difficult object, even in smaller scopes. You just need to know where to look. (and good conditions)

Whenever i show this object to someone who has never seen it, I always use a tiny parallelogram of stars as a pointer. Think the constellation Lyra. I've highlighted it in the picture below. I'll explain how it sits off the end of the parallelogram closest to M13. It's a great visual landmark to help people identify the small IC galaxy.

Next time you're out, try to use my technique in finding IC 4617. I'll bet it helps!

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Bertrand Laville
July 18th, 2019, 05:56 PM
Hi All,

An old sketch and study on surrounding stars of IC 4617.
Details: http://www.deepsky-drawings.com/ic-4617/dsdlang/fr

Clear skies
Bertrand
http://www.deepsky-drawings.com

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