King 1 and King 2 oc's in Cas...19th mag???

[Jraymond]

In Uranometria Deep Sky Field Guide , King 1 (chart 8) and King 2 (chart 18) are both listed as 19th magnitude. Anyone have a good explanation? I don't see the point.

Thanks
John

[wvreeven]

Simbad lists those magnitudes for those clusters as well. I couldn't find magnitudes for those clusters in Webda but perhaps I am not looking in the right place.


Clear skies, Wouter

[obrazell]

Seems to be in WEBDA http://www.univie.ac.at/webda/cgi-bin/ocl_page.cgi?cluster=King+1 and http://www.univie.ac.at/webda/cgi-bin/ocl_page.cgi?cluster=King+2 under photometry. The mags are in the 17's. Perhaps they are just in UA for completeness of that catalogue?

Owen

[Steve Gottlieb]

Here are my observations of King 1 and King 2, using my 18" in December 2011. I'm fairly certain I was observing the correct objects, though don't know whether the mentioned stars are actually members (or brighter superimposed stars). So, why not take a look and let us hear what you find?


King 1

Very pretty, rich cluster, spreading out over 8' to 10' in size. The stars are mostly contained within a triangular outline with mag 10 stars at the corners (sides of 8', 9' and 10'). Near the center of this triangle is Stein 40, a distinctive 9.8/11.9 pair at 13". At 175x, 75-80 stars mostly mag 13-15 are resolved. Within the triangle, the richest portion of the cluster is concentrated to the north of Stein 40, where the stars form a fairly uniform rich mat. About 12' N is a large, scattered group of a half dozen mag 10 stars and a several mag 12 stars that I initially thought might be King 1.



King 2

Picked up at 175x as a faint, roundish glow with only a couple of stars resolved. 285x improved the view and two brighter mag 13-13.5 stars were clearly resolved at the north edge (oriented N-S). Four or five additional 15th magnitude were resolved, three of these on the north side or center. Overall, the cluster appeared as a faint, unresolved, low surface brightness glow ~3' diameter, though a bit mottled at 285x. Located 28' NE of the pretty double star Eta Cas.

[Clear Skies]

King OC's are a CSOG edition, listed under Star Cluster Editions: http://www.clearskies.eu/csog/download/

Observation of King 1 - 12" SCT (179x / 27'), 14 October 2009 under murky Dutch skies:
Approximately 1/4 FoV in size. A mag. 10 star is on the NE edge, on the SW edge is a faint double star: a mag. 10.5 and mag. 12 star aligned NW-SE (= double star Stein 40). In between this double star and the mag. 10 star are a few mag. 12 stars with a background of faint unresolved stars. Recognizable as a cluster but very faint.

[Ciel Extreme]

I have an observation of King 2 with an 18" reflector at 295x: “This extremely faint cluster is not well seen; an extremely faint nebulous glow is suspected south of a N/S pair of stars of mag. +14 and two or three other very faint stars nearby which may be cluster members." My sketch agreed well with DSS image below.

2681

[Don Pensack]

King 1: Trumpler II2r, 9', 100 stars, brightest star mag.13
King 2: Trumpler II2m, 4.0', 40 stars, brightest star mag.17.0
Both pieces of information are consistent with Steve's descriptions.

[Jraymond]

So what you guys are trying to tell me, no one uses Uranometria DSFG. While the Willmann-Bell ads in SKy and Tel told me otherwise over the years.

I really suspect it's a misprint , 10th mag instead of 19th in both cases.

[Don Pensack]

So what you guys are trying to tell me, no one uses Uranometria DSFG. While the Willmann-Bell ads in SKy and Tel told me otherwise over the years.

I really suspect it's a misprint , 10th mag instead of 19th in both cases.

10th magnitude for a complete total integrated magnitude makes sense for King 1, but not King 2.
I trust the information in "Star Clusters" by Archinal & Hynes. If the DSFG differs, i'd discard what DSFG says.
Also, try NED and SIMBAD.

[Jraymond]

I forgot I had that book too!
No magnitudes given. :(

[Don Pensack]

Well, a total integrated magnitude for a star cluster isn't really very important.
The most important numbers are:
--magnitude of the brightest stars
--number of stars
--Trumpler Classification (see: http://www.astrophoton.com/trumpler_class.htm )
--and, for globulars, the magnitude of the Horizontal Branch, which lets you know how many stars you are likely to resolve

With an 18" dob, I would presume you could see every star cluster in the Milky Way that was not blocked or severely reddened by dust and distance.
And, in good seeing and pristine darkness, stars to about magnitude 17.5. Steve Gottlieb's descriptions are excellent.
In excellent seeing and darkness, you might see a handful of stars in King 2.

In my 12.5", I found King 1 to be an interesting target and like a small cluster filled with very faint stars.
King 2 had a few stars visible, but was mostly a small faint glow.