NGC6380 on star charts?

[The Mekon]

NGC 6380 - a faint globular in Scorpius. Plotted in my 1990 Sky Atlas 2000 as just south of Q Sco. This globular has always been very difficult. I failed to find it in the darkest skies with my 130EDT, asked others at Ilford to check in 10" 12" and 16" without result. Finally it was spotted in a 20" F4 Obsession (Jon Andersons?) All this would have been 20 years ago. Recently I have been searching for it in my 18" SDM. I should be able to see it, remembering the view in the 20" but nothing yet.
My question pertains to its plotting. In my more recent edition sky atlas, instead of NGC 6380, we have SL28 - a dark nebula! What is going on, just where is NGC 6380?

[Back Yard Boy]

By coincidence, I was searching for 6380 myself late last week - but was unable to find. The location I was searching is the same as what you have outlined - just south of Q. I have a 12" DOB and thought that I should be just able to spot this GC given that it was a reasonably dark clear night when I was looking.

I hope someone else may be able to answer your query, as I am curious myself to know the answer.

[mithrandir]

John, CdC plots NGC 6380 at Mean J2000 RA: 17h34m 30.0s DE:-39°04'00"
in the corner of SL28 Mean J2000 RA: 17h35m 18.0s DE:-39°14'00"

SL 28 is listed as 30x15 arcmin and NGC 6380 as 3.9x3.9 arcmin

In Uranometria 2000 Vol 2 NGC 6380 is on map 164. It should be tha same map number in the one volume edition.
In The Night Sky Observers Guide Vol 2 they are both on page 348.

[Weltevreden SA]

John, by itself 6380 by itself is not all that hard to spot, but it's highly obscured by galactic extinction, so its listed visual mag of 11.1 is actually a surface brightness of 18.0. This is made much worse by a distracting 10.6 mag field star nearly on its so. edge. Even so, once I finally spotted it, I now see it easily on any decent night in a 150mm MK66 Mk at 60x, appearing like a slight cometary or nebular flare right next to the star. It's easier in a 180mm scope at 170x and now I use it as a test for transparency.

Andrew gave good chart instructions. Here are some tips: the bright star in 'NGC locator 1' attached is HD 159433 at vmag 4.3. Just SW (at 4:30 in the image) is a 4-star asterism that looks a bit like the head of Draco. Follow the two faintest stars directly towards 4:30 to HD 159073, the distracting mag 10.6 star. Visually the Draco head is easy and not confused with all the field stars as seen in the attached WikiSky image #1. HD 159073 looks a lot fainter visually than the attached DSS image #3 would indicate. Once you have it, go up to around 175-200x and 6380 will appear glued to the star, a faint glow that to my eye looks no larger than 2' dia visually.

SL 28 is the dark mass SE of 6380 in the attached image #2.

NGC 6380 is no friendlier to the professionals than to us. There are only a couple of papers devoted to it, the most detailed being (Ortolani et al, Astron. Astrophys. Suppl. Ser. 127, 471-477 (1998). It has a minor claim on galactic specialness because it's right on the edge of the Galactic bar, a region that has considerable gas flow taking a sharp left turn from the innermost spiral arm to funnel down the bar into the bulge. It's tempting to consider it a breezy place to live except that the breeze is only about 10,000 atoms per cubic cm, which is several thousand times less dense than the best earthbound lab vacuums. OTOH, the breeze is whisking along at a sprightly 67 kms a second. If you had a cat, it's whiskers might twitch. (Not if it's my cat, though, which only wakes up at the breeze of its food dish being filled.) That gas flow into the bulge is one reason why there are some 15 fairly young globulars in the bulge. 6380's [Fe/H] metallicity is -0.5, which, with other arcane details the astronomers adore, dates it being about 6 billion years old. It's a relative youngster out there. That doesn't mean the bar itself is that old; instead, some astronomers think galactic bars are a transitory feature that form and fade over several billion-year life cycles. There's some, but not conclusive, evidence that the bar that fed 6390 and a number of other bulge globulars of the same antiquity came and went a long time ago and the present bar is actually feeding yet another generation of globulars not even born yet. You can check back in 5 billion years or so to see if it's all true.

Let us know how the search comes out.

=Dana in SA

[astroron]

I have observed this object frequently over the years.
The first time I saw it was at Illford throughin Mike Kerr's 20" scope,eeven he didn't spot it till I pointed it out.
It does require good seeing to observe it, but is seen in my 8" SCT from my place in Cambroon, which has a pretty dark sky.
As noted by Dana the 10.1 star close by makes it a bit of a difficult target if you don't have good seeing.
Cheers:thumbsup:

[ChrisRS]

I spent best part of an hour looking for NGC 6380 2 nights ago in good conditions, with my 12" scope, but failed. I used the 4 star asterism as a guide, so I know I was in the right area. I also dipped out on globular cluster Tonanzintla 2, which is close to NGC 6380, close to star HD 6546. I'll try again when the conditions are good.
These globulars close to the galactic plane are often difficult, but the biscuit must go to 2MASS-GC01 , about a degree west of Mu Sagittarius, Uranometria map 145. The literature gives the visual magnitude as +27.7 - just a tad beyond my capacity.

[The Mekon]

Thank you all for the responses. And especially Dana from SA with the additional information. I'm impressed that you have seen this in a 6" Mak, your skies must be pretty good! Tonight is cloudy so no show, I will keep looking and hopefully succeed now I have a few tips to act on.
John

[noeyedeer]

... from deep sky hunter - chart 81, might help as well. if you don't already have it its an excellent free atlas. I can't remember where I got it from but it was from a link off IIS
Happy hunting
matt

ps.. does this put it where your atlases place it?

[Weltevreden SA]

You can download Michael Vlasov's 'Deep Sky Watch' here (tp://www.deepskywatch.com/deepsky-atlas.html). Print it in A3 format and it's a spectacular field set. That said, it doesn't show the 6380 field in detail, especially the 'Draco head' asterism that makes 6380 easy to find. Alvin Huey's 2013 'Globular Clusters' (http://faintfuzzies.com/DownloadableObservingGuides2.html) (90 of them, oh my) Chart 63 locates 6380 quite well, as does J.R. Torres' Tri-Atlas (http://www.uv.es/jrtorres/index.html) 'C' set (stars to vmag 13.5, DSOs to 15.5). The 'C' set runs to 571 charts—don't print in A3 unless you've just won a lottery. The number '6' in Torres' '6380' (centre bottom) covers the 4th 'Draco' star, but shows the vm 10.6 HD 159073 well.

If you'd like to practice mentally blocking an irritating field star next to a GC, you can try NGC 5634 in Virgo near the Libra border. It's on Huey's Chart 27 and is 2 full vmags brighter than 6380; the adjacent field star is vm9.5. NGC 5634 has the distinction of being a tidally stripped GC from the same Sagg Dwarf that gave us M54 and NGC 4717 Coma. Actually, there's a lot of tidally stripped GCs in the MW—all of the retrograde-motion halo globulars were appropriated by the MW after a series of rather messy divorces (for galaxies, that is).

[mithrandir]

That's map C457 to save hunting. It also shows TON2 (but not HP1) from another thread.

The Triatlas "C" set of maps is available for free on iTunes. About 100MB. It contains the index map and all the submaps. There's essentially no doco for the app but I found that tapping on an adjoining map number takes you to that map.

[astroron]

Not impressed with this map, it shows NGC6380 in isolation when in fact it has a 9.8 star superimposed on one side which adds to the difficulty of seeing this object.
Cheers:thumbsup:

[noeyedeer]

thanks for the heads up Ron. should I disregard it completely or just be aware that it's not as accurate as some of the others?

there is a mag 9 or 10 (not sure if they round up or down or at all) dot to the bottom left of the centre of the crosshairs, bearly noticable. Looking on the other charts it should be on the right hand side and not as close to the centre. the map only shows upto mag 10.2 stars.

I might have to obtain deep sky watch as recommended by Dana, actually I won't because its quite similar to the one I have, (I fact it is the one lol) ... I'll take look at some of those books on faint fuzzies for a browse. thanks :)

matt

[astroron]

I would go for a more accurate map,That star you mention in the cross hairs,which I admit did not see,at the scale of the map would be about 13mag.
If you have a look at the images presented on this forum, you will see how bright the star is compared to the cluster.
The cluster is in a very starry part of the sky and so can be overwhelmed by the background stars of the MilkyWay.
It really is a good observing target as only seasoned observers have seen it that I know off.
Best of luck :)
Cheers:thumbsup:

[noeyedeer]

Thanks Ron,
I was trying to compare the map to the images and that's why I posted the chart just so I had some input on the accuracy. its no biggie as I don't have dark enough skies to even try to find it, let alone observe :)

its all good, might be something I can try to hunt down when I do go out bush with a dob, but that certainly isn't any time soon.
thanks again
matt

[glenc]

The attached wikisky.org image shows N6380.
It is 35.4' SSW of the mag 4.3 star at the top left.
Note the four "bright" stars between them and the mag 9.8 star on the southern edge of 6380.
N6380 is difficult in my 16" scope because of that star.
John Herschel discovered N6380 with an 18.5" speculum reflector.
Ton 2 is 6.8' NW of the mag 4.3 star. (see Huey's map in post #9)

[SteveG]

There really was an error in the original Sky Atlas 2000.0 position and a number of other sources from that era!

The position (1950 coordinates) in Hartung's 1968 Astronomical Objects for Southern Telescopes was 1.0 minute of RA too far east -- that's roughly 11.5 arc-minutes. Sulentic and Tifft's 1973 Revised New General Catalogue (RNGC) of Non-stellar Astronomical Objects has the same mistake though the error may have originated from an earlier globular cluster list.

In any case, once an error like this gets started it often has a life of its own -- the wrong position (in RA) is found in Roger Sinnott's 1988 NGC 2000.0 (now updated to 2000 coordinates, of course). Then the position was plotted incorrectly (too far east) in the first version of Tirion's Sky Atlas 2000.0, and the coordinates are wrong in the first version of the companion Sky Catalogue 2000.0. Finally, even the first edition of the Uranometria 2000.0 Atlas had NGC 6380 plotted at the wrong position!

And these are the only sources I know about as I have personal copies. Of course nowadays you'd hope that printed atlases, catalogues, online sources, and planetarium software all have the correct positon.

But if anyone can track down where this problem originated, I'd be interested in knowing.

[Regulus]

Cheers - Trevor