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Thread: Globular Cluster hunting -- in Barnard's Galaxy!

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    Member Steve Gottlieb's Avatar
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    Globular Cluster hunting -- in Barnard's Galaxy!

    During the July new moon window I observed for 4 nights at Grandview campground (8600 ft elevation), situated in the White Mountains of eastern California, just below the Ancient Bristlecone Pine Forest. I met a group of friends including Paul and Debbie Alsing, Kemer Thomson, John Hoey (all from the San Diego area), Jimi and Connie Lowrey (from west Texas but drove directly from Florida) and Carter Scholz and Rick Linden from the San Francisco east bay. The weather turned out great and the Detwiler fire southwest of Yosemite didn't impact us, though I drove through the heavy smoke in Yosemite to reach the site on the 18th. SQM-L readings were generally in the 21.65-21.80 range, though occasionally below 21.5. The largest scope was Rick's 32" Webster, which nearly dwarfed my 24" Starstructure.

    One highlight for me and Jimi was a Sagittarius globular that actually resides in Barnard's Galaxy (NGC 6822), a local group dwarf. A bit of background first -- Edwin Hubble was the first to investigate Barnard's Galaxy in detail in 1925 seminal paper "NGC 6822, a remote stellar system". He found 10 nebulous objects (labeled with Roman Numerals) within Barnard's Galaxy. Most of these are HII regions (the best two visually are Hubble X and V), but Hubble VII turned out to be a bonafide ancient globular. The location, though, creates a problem -- its a tiny 16th magnitude speck superimposed on the glow of the galaxy and a very nasty visual target. I was successful observing it twice back in 2010 with my 18", though it was quite challenging to identify within the mottled glow (barely non stellar and lost in a maze of other dim stars within the galaxy). I figured that was probably the last GC I'd see in Barnard's Galaxy.

    The following year, four new Barnard Galaxy globulars were announced in 2011 by Hwang et al, though these seemed too faint as visual targets for my 18". Then in 2013 three additional GCs were identified in Barnard's Galaxy by Huxor et al, bringing the current known total to 8. It looked like globulars #6 and #7 (called SC6 and SC7) were reasonable targets for my current 24", though when I added these to my observing list I had no idea what to expect as I haven't run across any amateur observations of these globulars.

    SC 7 is in the outskirts of Barnard's Galaxy, 22' NE of the center of the galaxy and well outside the visual extent of the galaxy at low power. But that makes identification much easier as the surrounding star field is not a mess! Once the general field was centered using a 6mm Delos (375x in my scope), both Jimi Lowrey and I were surprised to quickly notice a non-stellar glow without first examining an image of the galaxy. SC 7 was fairly faint but clearly non-stellar, roughly 6"-8" diameter and perhaps 15-15.5 magnitude. The globular could be held steadily when we backed the magnification down to 282x and possibly had a brighter stellar nucleus.

    A 2015 paper by Veljanoski et al titled "The Globular Cluster System of NGC 6822" shows the relatively positions of the 8 known globulars and provides coordinates, projected radii, GC type (compact or extended), half light radius and interstellar reddening. In addition, it derives the following V magnitudes, along with the following positions --

    SC 6 19 45 37.0 -14 41 10.8 15.4V
    SC 7 19 46 00.7 -14 32 35.0 14.8V

    At a distance of 1.6 million l.y., the globulars in Barnard's Galaxy are 4 or 5 times the distance of the outer halo globulars in our own galaxy. I didn't have a chance to go after SC 6, which I hope to track down next month. I'm guessing an 18" might be close to the minimum aperture to track these down, but who knows if you don't try. If anyone else takes a look, post your observations!

    post-29260-0-28916400-1501384251.jpg
    Steve
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    Big Jim Jim Chandler's Avatar
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    The Texas Star Party 2008 Advanced List included SC 6 & 7, so I expect that there are a number of amateur observations of both objects. I viewed them on 6-2-2008 using my 30" f/4.5.
    SC 6 & 7 were both easily seen at low power (Pan 41, 82x) as stellar objects. SC 6 remained stellar even at higher power (Nagler 9, 372x), but SC 7 at 372x presented as a fuzzy disk, obviously non-stellar.

    Two other objects in NGC 6822 were seen that night, OB associations 8 & 13. Both were seen at low power as dim glows and at higher power appeared as fairly bright and mottled.
    Jim

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    Member Steve Gottlieb's Avatar
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    Thanks, Jim, for posting the observations. The two globulars I mentioned (SC 6 and SC 7) in the post were discovered more recently than Larry's list, so are definitely different! The ones he included on the 2008 Advanced Observing list were discovered by Hubble and included in the 1925 paper I referenced. Hubble used Roman numerals designations, VI and VII, though let's call them H-VI and H-VII. Talk about confusing and misleading nomenclature. We have two different globular clusters in Barnard's Galaxy -- Hubble's H-VII as well as the new SC 7!

    Here are my notes on H-VII from August 2010: 18": Extremely faint and small glow, ~10" diameter. I couldn't resolve the adjacent mag 16 star on the SSE edge, but the glow was definitely non-stellar.

    I don't know if SC 6 and SC 7 are in SkyTools, but use the coordinates in my original post if you'd like to add to your large globular list!

    ---

    I just noticed that the OB associations 8 & 13 on Larry's TSP list correspond with Hubble's V and X, which are the two most prominent HII complexes at the north end of the galaxy.
    Last edited by Steve Gottlieb; July 31st, 2017 at 04:03 PM.
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    The only two objects in NGC 6822 that SkyTools knows of are MCG-2-50-2 and MCG-2-50-3. IC 1308 is not known by SkyTools and neither are the other objects mentioned.

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    Is IC 1308 real? Megastar has it as unknown so perhaps that is why it is not in SkyTools. I do note that there is nothing about it in Harold Corwins IC notes so perhaps it is real and there as a propagated error in the charting programs, not unheard of.

    All of the other stuff would be too deep for SkyTools. Greg and I have had discussions over this stuff and he feels that in most cases it is too specialised for his target audience. They can of course be added via the supplementary database.

    Owen

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    Member Steve Gottlieb's Avatar
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    Quote Originally Posted by wvreeven View Post
    The only two objects in NGC 6822 that SkyTools knows of are MCG-2-50-2 and MCG-2-50-3. IC 1308 is not known by SkyTools and neither are the other objects mentioned.
    That's unfortunate since IC 1308 = Hubble X as well as Hubble V are much more prominent visually than MCG-2-50-2 and MCG-2-50-3! The MCG designations are really a misclassification in the first place, since the MCG is a galaxy catalogue and these are giant HII regions within the galaxy. Because of the MCG error, these two object also carry PGC designations! Here's a summary of the various Hubble objects (from 1925) --

    Hubble I (AKA: MCG -02-50-002 = PGC 63596)
    19 44 31.8 -14 41 57
    HII complex

    Hubble III (AKA: MCG -02-50-003 = PGC 63600)
    19 44 34.4 -14 42 20
    HII complex

    Hubble V
    19 44 52.2 -14 43 09
    bright HII complex

    Hubble VII
    19 44 55.8 -14 48 56
    globular cluster

    Hubble X (AKA: IC 1308)
    19 45 05.3 -14 43 16
    bright HII complex
    -------------

    Recent discoveries (2013)

    [HFV2013] SC6
    19 45 37.0 -14 41 11
    globular cluster

    [HFV2013] SC7
    19 46 00.8 -14 41 11
    globular cluster


    Here's the HST image of Hubble X --

    web_print.jpg
    Last edited by Steve Gottlieb; July 31st, 2017 at 04:41 PM.
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    Member Steve Gottlieb's Avatar
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    Quote Originally Posted by obrazell View Post
    Is IC 1308 real? Megastar has it as unknown so perhaps that is why it is not in SkyTools. I do note that there is nothing about it in Harold Corwins IC notes so perhaps it is real and there as a propagated error in the charting programs, not unheard of.

    All of the other stuff would be too deep for SkyTools. Greg and I have had discussions over this stuff and he feels that in most cases it is too specialised for his target audience. They can of course be added via the supplementary database.


    Owen
    IC 1308 = Hubble X is certainly real, despite not being recognized by Megastar. In fact, the original IC position lands right on top of the HII region and Hubble's seminal 1925 paper on NGC 6822, mentions his nebula X is identical to IC 1308. But more recently Paul Hodge's 1988 paper "The HII regions of NGC 6822" (PASP, 100, 917-934) failed to label Hubble X as IC 1308.

    There's an interesting story behind this number. Francis Leavenworth, an astronomer at the Leander McCormick Observatory in Virginia, discovered this object on 18 Jun 1887 using their 26-inch Clark refractor. Because of the small field of view in the large refractor, Leavenworth missed seeing the entire galaxy but he picked up the two bright HII regions at the north end of the galaxy instead. But he mistakenly assumed the small HII now called Hubble V was actually Barnard's Galaxy, so he only claimed one new discovery! If it wasn't for this mistake, both of these (relatively) prominent HII regions would have IC designations.


    Personal rant: In general, Megastar did a poor job on the identification of the fainter IC objects as it wasn't based on the NGC/IC Project (neither is SkyTools, I believe). In several hundred cases, perfectly good IC objects weren't recognized or Larry Mitchell assigned MAC designations. A few examples are IC 15, 28, 36, 47, 88, etc. If you look up these numbers in Megastar, you'll see what I mean. The reason this probably occurred is these faint IC galaxies were missing in the original PGC, so Larry assumed they were uncatalogued. In fact, even today LEDA fails to recognize many IC designations! For example, PGC 1175571 = IC 88, though Larry assigned it a MAC designation and HyperLEDA doesn't know about the IC number!
    Last edited by Steve Gottlieb; July 31st, 2017 at 05:25 PM.
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    No Greg does not believe in the historically corrected NGC/IC project for some reason. He is quite adamant about not using it. Megastar 5 did not use it because of licensing issues but I believe if there ever had been a Megastar 6 then it would have used this.

    Owen

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    Member Steve Gottlieb's Avatar
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    Agreed, Owen. I should add that Harold Corwin loaded his historically corrected identifications/positions into NED a few years back, so although it looks like we'll never see an updated Megastar, at least NED identifies all of the NGCs as well as those hundreds of ICs (such as IC 88) correctly.
    Steve
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    Big Jim Jim Chandler's Avatar
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    Quote Originally Posted by Steve Gottlieb View Post
    I don't know if SC 6 and SC 7 are in SkyTools, but use the coordinates in my original post if you'd like to add to your large globular list!
    They are not in SkyTools, but the trusty Supplemental Database tool will take care of that. It's nice to have some new GCs at visible wavelengths to attempt! It gets a little frustrating trying to see infrared objects visually.
    Jim

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    Member gdjsky01's Avatar
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    Quote Originally Posted by obrazell View Post
    No Greg does not believe in the historically corrected NGC/IC project for some reason. He is quite adamant about not using it.

    Owen
    SHOCKING!
    Given the reliability of Skytools (1 through 3) as a program (I can crash it generally with 30 minutes) this comes as a great surprise. (not!)
    Oh well. Off topic...
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    Interesting. I have been using SkyTools a lot over the same time frame and I don't think I have ever crashed the program.

    Owen

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    Member Atlas's Avatar
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    Hi Steve,

    last summer we had a long thread about the SC's in Barnard's galaxy in the German deep sky forum. There were several reports of sightings of SC 6 and 7. In my 25" I could see them both easily, but failed to detect SC 1.

    http://www.astrotreff.de/topic.asp?TOPIC_ID=197206 (scroll down a little)

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    Member Don Pensack's Avatar
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    Hmm.
    Is there ANY computer atlas that does incorporate the Historically Correct NGC/IC?
    Don Pensack
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    Member Steve Gottlieb's Avatar
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    I'll check with Wolfgang, but yes, I believe there are several.
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    Don I think the challenge here is that Wolfgang licenses the use of this data set (for money I assume) therefore many people who do not want to pay a fee use other datasets or start their own. There is now an OpenNGC project started because of this issue. So you will not find any of the free software using Wolfgangs data. As you are well aware there have been very few new programs released in the last few years and because of this even those that did use the corrected data from Wolfgang (which is not the same as the data from the NGC/IC project site for various legal and political reasons, at least currently) is both limited and not up-to-date. it is not clear to me at least when there will be any new software coming out. ST4 has been in the works for years and if/when it comes out will not be probably until 2018 at least and as noted even if Greg has updated his NGC/IC data to use the latest from NED he still has an issue with the whole corrected NGC/IC concept.

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    Member Steve Gottlieb's Avatar
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    Here's at least a partial list of software that I believe are using Wolfgang's corrected NGC/IC databases. I don't know, though, if all of these are currently supported programs ---

    Mathematica, TheSky X, Guide, SkyMap Pro, Voyager (MacOS and Windows), Starry Night, Eye & Telescope, Deep-Sky Planner, Xephem, Cartes du Ciel, c2A, database for the Losmandy mount.
    Steve
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    Hi Steve - the latest versions of CdC use the OpenNGC project data not Wolfgangs. E&T is no longer available and the only one I think with up-to-date data is DSP. The others may use it but programs like Guide have not been updated in many years, particularly with regard to their databases. The same probably applies to most of the programs in that list.

    Owen

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