Object of the Week July 3rd, 2016 - NGC6946 The Fireworks Galaxy

NGC6946
UGC11597
Arp 29

Cygnus

Galaxy

RA 20 37 52
DEC 60 09 15

Mag: 8.8

Size: 11.6' x 9.8'

Class: SAB(rs)cd

What a better way to pay tribute to Americas independence this week than to discuss our own deepsky fireworks! NGC 6946 or the Fireworks Galaxy, is a beautiful face-on spiral located in Cygnus near the border of Cepheus. Discovered on September 9th 1798 by William Herschel, 6946 makes its fame for not only being a wonderfully visual deep sky object in a telescope, but it claims title as being the most active galaxy as far as supernovae observed. Since 1917, we have observed 9 supernovae within NGC6946, with the most recent being in 2008 by UK amateur Ron Arbour.

Visually, a relatively close neighbor at only 18Mly, NGC6946 makes for a marvelous object. Between its spiral arms, its numerous challenging HII knots brought to our attention by our own Steve Gottlieb in his July 2013 issue of Sky & Telescope to its beautiful counterpart NGC 6939, an Open Cluster just over the border in Cepheus, these objects offer a wonderful sight in all sizes of telescopes. Lower power wide field views offer a stunning "Two-Fer" in the eyepiece, two differing objects visible in the same FOV.

Lastly, DSF had a short thread in 2013 touching upon those HII regions Steve mentions in his S&T article. You can find that thread here: http://www.deepskyforum.com/showthre...highlight=6946

For even further information, Universe Today has a great article located here: http://www.universetoday.com/17824/t...dietmar-hager/

So next time you're out under some dark summer skies, be sure to swing north and find some fireworks in NGC6946. Just how many knots can you see?

Give it a go and let us know!

Attachment 2179

This is a beautiful galaxy and a beautiful couple with the open cluster. I can contribute a drawing from 2012 with my 4" Newtonian. The spiral structure was visible but very difficult.

4", 40x (1.8° field):
Attachment 2181

And an inverted, rotated and cropped version:
Attachment 2182

I reobserved this galaxy a few nights ago with 12" in SQM 21.9 skies and noted the main familiar features. Observing with 16" from the same site three years ago (SQM 21.7 on that night) I recorded that the pair was nicely framed by the 2" Pentax. The cluster was grainy with partial resolution. 225x brought out the "rounded-tipped angle of stars in the cluster, as described by William Herschel". The galaxy sketch from that observation is below (140-225x). "a" and "b" are my own designations; H are Hodge (1969) HII regions, A are Ivanov and Krastev's (2000) OB associations, and HB are HII regions from Bonnarel et al., 1986.

http://2.bp.blogspot.com/-Df5TB5ZpNu...946+marked.jpg

This was one of my favorite galaxies in an 8" telescope, just because of the challenge it presented under poor sky conditions. My friend and I used it for a while as a measure of sky quality.

This beautiful spiral is so heavily obscured by galactic dust. I find it challenging to see detail in my 18", but here's what I logged under the exceptional skies of Okie-Tex Star Party 2015:

14mm Pentax eyepiece. Beautiful. Careful observation resolves spiral arms. Knot observed without UHC, but UHC seems to kill it. Galaxy dimly visible with UHC.
Attachment 2186

I didn't know about Steve's article on the knots. Next time I give it a try, I'll make sure I have Steve's article with me.

Clear Skies

Regards
Akarsh

Nice spiral Dragan.

My past 5" binocular did not bring out any detail, but shows nice views together with NGC 6946.
20x125, NELM 6m0+
Attachment 2194

More intensive views with my former 14.5" shows the faint spiral structure with some HII regions, especially the huge SSC NGC 6946-1447.
14.5", 202x, NELM 6m5+
Attachment 2195

Some actual attempts to show details (clusters) within NGC 6946-1447 failed. I once had a quick and dirty look years ago under superb seeing which shows some stellar peaks within the SSC.

Better late than never, here's my most recent observation and sketch of 6946:

"Using the photo from Steve G's S&T article (July 2013 issue) I tracked down all the HII regions... 408x, 21.70 SQM"

Attachment 2280 Attachment 2281

I want to make another sketch, hopefully next year, when 6946 is near the meridian because my last few attempts were when the galaxy was well down in the sky. There's a lot to see in 6946 but most of it is rather subtle.