Ngc 6749

[Preston Pendergraft]

I was able to get out last Saturday night and catch some more globulars. Most were pretty easy, being they were from the Herschel or Messier catalogs. I am currently completing the Globular Cluster pin from the Astronomical League and there are four clusters that are to be used as guides for classifying the clusters. One of these is NGC 6749 and I tried to observe it Saturday night and I didn't see anything. I had the proper field and everything

Has anyone looked for this cluster? The NSOG books have a description for larger scopes but not from the 8-10in class.

[Clear Skies]

NGC6749 will be a real challenge for a 10" scope. I observed it using my 12" SCT under good conditions and found it to be "on the limit": An extremely faint, round patch, on the threshold of visibility, only visible when using averted vision, completely unresolved. Immediately to the SE is a trapezium of mag. 12 stars.

This may help in pinpointing the cluster's location: NGC6749.jpg
The two mag. 8.5-ish stars to the northwest should make for a nice lead-in feature. Image size is 30'x30'.

Good luck!

[Steve Gottlieb]

NGC 6749, along with NGC 6380, are probably the two faintest globulars in the NGC. I also found it difficult in a 13" back in 1985 (described as "extremely faint, moderately large, very low surface brightness and fades at high power"). In fact, it's not exactly a showpiece in my 18" (observation below). An interesting historical question is whether this highly reddened globular should be identified as NGC 6749!

The only historical observation comes from John Herschel on 15 July 1827 when he described "a cluster of loose small stars of various magnitudes; fills the field." His position is about 8' off from the globular, but everyone has assumed that's the intended object.

But the globular is only 3' or so in diameter visually and would have been unresolved in his telescopes. To me, that doesn't correspond with a object that "fills the field" and consists of "loose small stars of various magnitudes. Instead, Herschel's description may apply to the general Milky Way field which is very rich. He did include a number of rich Milky Way fields that apparently caught his eye in his catalogs and this may be another case. At this point, though, even if I'm correct the globular is not going to lose its NGC designation.


18" (8/2/11): this challenging NGC globular is highly obscured and just stands out clearly from the rich Milky Way background glow. At 225x it appears as a very faint diffuse glow, roughly 2' diameter, with a low surface brightness and a small brighter core. A 12th magnitude star is superimposed and the slightly brighter core of the globular is located about 45" SW of this star. The edge of the globular is not well defined but appears to just reach a mag 12.5 on the south end. Additional mag 11-13 stars are clearly off the east, west and south side of the halo. Four mag 12-13 stars just off the south side form a small trapezoid that helps to pinpoint the location of the globular. Located 26' ENE of mag 5.8 HD 177178.

[Preston Pendergraft]

Wow thanks for the response Steve, interesting history on the object. I think this might be an object that I save for Texas Star Party and those inky dark skies of west Texas.

NGC 6380 appears to be another globular cluster, I will put that one down as another to do under darker skies then what I have in Alabama.