NGC 6946 article in July issue of S&T by Steve Gottlieb

[Howard B]

Hats off to Steve for another terrific observing article in the July issue of Sky & Telescope about NGC 6946. I'll certainly have this article with me at the GSSP next month to see how many HII regions I can track down!

[Jimi Lowrey]

I am with you Howard "Hats off to Steve" Great read about a awesome galaxy.

[gdjsky01]

I observed four of the seven through a 24 f/3.7 at the recent GSSP. I believe they were 1 through 4.

[Ivan Maly]

I finally reobserved this galaxy in detail last night. Regions Gottlieb 1, 2, and 5 were visible as such - as compact enhancements.

I don't know what Steve thinks about these "Gottlieb" designations that I use, but this is what you get for publishing a journal article with what amounts to a catalog of objects. In the other forum I offered some identifications with professionally cataloged HII regions (and Steve kindly corrected some of them), but in truth these visually prominent enhancements are not identical with HII regions that coincide with them - they are also clumps of starlight. I am not aware of a catalog of stellar associations in this galaxy, so even a clumsy double HII/SA designation in this case is impossible. A visual catalog like the one (effectively) offered in this S&T article is actually what we need.

Regions 4 and 3 were not distinguishable as such but resided in the brightest spiral arm segment (NE of the core), and 6 and 7 were probably primarily responsible for the visible extensions of the two arms on the WNW side. Besides these, a broad star cloud located just distally down the arm from Gottlieb 3, and an enhanced segment located proximally from Gottlieb 7 in another arm were quite prominent. The latter unnamed segment is very subdued in the photo in Steve's article (some professional photo it seems). I think less or more uniformly processed photos out there show it better.

Apart from the dominant arm stretching E, this is all pretty difficult detail and required time.

16", 140 and 225x, SQM-L 21.69.

West up, north left.

2013-08-14 NGC 6946.jpg

[Howard B]

Hi Ivan,

I had some excellent views of 6946 at the Oregon Star Party last week and also used Steve's article as my guide. I was able to track down all the "Gottlieb" designations, one of which was real bugger, and will post my sketch and observations as soon as I scan my notes. I agree, this is a low surface brightness galaxy that surrenders its detail reluctantly and requires dark, transparent skies to see much at all.

[Howard B]

I've finally gotten around to scanning my notes from the 2013 Oregon Star Party so here's my unfinished sketch of NGC 6946. Using Steve's July article in Sky & Telescope as my guide I went after the eight knots he identified and was - barely - able to see them all. The toughest knots in the spiral arms were 6, 7 and 8 from his article, with 6 by far the most difficult. All I could see of 6 at first was a star at this position until the sky became more transparent and suddenly a small bit of fuzz became visible using determined averted vision. Many of these knots need to be specifically looked for because they're too subtle to jump out on their own, so Steve's article was a really helpful observing guide. I used magnifications from 253x to 408x for this sketch, and the darkest SQM reading during sketching as 21.73.

N6946 bigsketch_crop.jpg N6946 bigsketch_invert.jpg

[Ivan Maly]

Wonderful observation, Howard!

Surprising is the extreme faintness of the arm leading to knot 7 in your view. The inner side of the arm there is one of the most robust regions in the galaxy - although the artists behind the S&T photo brushed over it.