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Thread: The "7331 Gang"

  1. #1
    Member ChristianR's Avatar
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    The "7331 Gang"

    NGC7331, also known as Cadwell 30, is a spiral galaxy about 40 million light-years away and located in the northern part of the constellation Pegasus.

    With a brightness of 9,5mag it really isn't a difficult object and well known. However, there are a number of interesting, smaller and much fainter companions.

    I observed the object with my 12" dobson under very good conditions in the Alps and was able to identify four members of the "7331 Gang", i.e. 7335, 7336 (the most difficult one), 7337 and 7340.
    ngc7331_Group_201310_comp1000.jpg

    labeled sketch
    ngc7331_Group_201310_besch_comp1000.jpg

    As outlined above, there are more galaxies within the field around 7331 which may be reached with bigger aperture (or same/smaller one?).

    I'd be interested in experiences, either the observation of additional field galaxies, or even internal structures of 7331.
    Clear Skies, Christian

    http://www.licht-stimmungen.de/
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  2. #2
    Member Ivan Maly's Avatar
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    I see that you caught the most contrasty spiral segment SW of the NGC 7331 core. I am still working on the details in this galaxy. This is my latest sketch made with 16":



    and the observation notes are here. The striping N of the core is an artifact of the rough sketch; the other details are real. The sketched area actually does not include the farthest of the four main satellite (or "satellite") galaxies.

  3. #3
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    Excellent observation Christian.

    Your conditions had to be very good, not easy to pick up all four companions of NGC 7331 with a 12" telescope.

    I got also all but with ~50% more light collecting area (sketch with 14,5")
    Clear Skies, uwe
    http://www.deepsky-visuell.de
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    27" f/4,2

  4. #4
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    I've seen all four shown here with my 12" Meade Lightbridge and 9mm ES100 under good, rural skies. NGC 7331 showed vague hints of its dust band. There's a companion galaxy on the other side of the galaxy as well, that's also visible in a 12".

  5. #5
    Member akarsh's Avatar
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    I didn't notice that there are these 4 neighbours. Might try the next time I get a chance to see NGC 7331.
    18" f/4.5 Obsession dob "Romela"
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  6. #6
    Member MarcE's Avatar
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    I also like this Group very much and observed it quite often with different apertures over the last years.
    Last year i used my old 10 inch GSO at Edelweissspitze in the alps and tried the Group again - with success.
    All 4 companions were visible with a 6mm Ethos. Most challenging was NGC 7336, which i only could see for a few moments with indirect Vision. The other companions were quite easy to observe.
    Marc

  7. #7
    Member akarsh's Avatar
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    Saw all four members with my 18" from Texas Astronomical Society's observing site near Atoka, OK. Skies were transparent, but there was considerable light pollution (maybe Bortle 3 ~ 4 or so).

    One of the four was considerably more difficult than the other three. Observation made with 10mm Delos.
    18" f/4.5 Obsession dob "Romela"
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  8. #8
    Member Marko's Avatar
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    Certainly a favorite here too and always worth a visit to this group.

    This group is a good group to judge conditions. The 4 members off to one side are often called 'The Fleas' because the whole group somehow got a name that stuck to it of 'The Deerlick Group'. The name has nothing to do with it's shape or anything but rather that was where some observers where that then started talking about it online so the name stuck. I think it was from Deerlick Astronomy forum and site is the way the name came about best I recall.

    To see all 4 fleas in a 12" is quite an accomplishment indeed and well done. I have seen firsthand in the past that altitude (in this case the Alps) greatly decreases extinction and this sort of object would be possible. 'Altitude ... Accept no Substitute'. From low ground to see this in a 12" would require a mighty clear and still night but Ngc7331 is certainly possible in much smaller than 12".

    When I visit this group (many times a season as I use it for judging transparency) I most always cannot resist a swing down SSE by 30' to Stephan's Quintet or Hickson 92 (which contains Ngc7320 for chart readers). Last month I could only barely detect 7336 in my 18" so I knew it was an off night.
    Let me roam the deep skies and I'll be content.
    Mark Johnston
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  9. #9
    Member Clear Skies's Avatar
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    7331 is a great galaxy by itself. I rate it a 7/10. Its companions are a great challenge.
    Two observations using a 12" SCT, both at 179x.

    30 September 2011 under light polluted Dutch skies, SQM 20.08:
    NGC7331 is the western galaxy, elongated NNW to SSE, large and brighter in an elongated central part. When not using AV the central part appears less elongated. The very bright nucleus is visible without AV.
    1/4 FoV to the ENE is a flattened triangle of stars pointing west (mag. 10) with the base on the east side aligned north (mag. 11) to south (mag. 10.5). Directly SSE of the mag. 10.5 star in the base is a small, round patch (NGC7340). To its SW (to the SE of NGC7331) is another small, round patch (NGC7337). To the WSW of the triangle of stars are two mag. 12 stars aligned NNW to SSE, to the west thereof is a slightly north to south elongated galaxy (NGC7335). NGC7336 is not visible.


    5 September 2013 under much better skies in northern France, SQM 21.12:
    NGC7331, the large western galaxy is very bright, elongated NNW to SSE. Brighter to the east of the center and slightly flattened on the west side from NNW to SSE. Brighter in the central part that is slightly elongated in the same direction with a bright nucleus that is clearly visible without AV. Using AV the outer halo of the galaxy clearly stretches out from NNW to SSE.
    To the ENE is NGC7335, slightly elongated NW to SE, even in brightness without AV, using AV slightly brighter in a small, round central part.
    To the NE is NGC7336, sometimes jumps into view as a small, round patch, on the limit of visibility, the faintest galaxy of the group.
    NGC7340 is a small, faint, round patch to the SSE of a very flattened triangle of stars pointing WNW (mag. 10).
    NGC7337 is a small, faint, slightly north to south elongated patch, the second faintest galaxy of the group. On the SE edge is a mag. 12 star. To the east is a mag. 12.5 star, twice as far to the WSW is another mag. 12 star.
    1/3 FoV to the NW is the galaxy NGC7326.


    7331csog.jpg
    Victor van Wulfen

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  10. #10
    Member akarsh's Avatar
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    Hi

    I'm in India for vacation now, and we were conducting a practical astronomy workshop under some reasonable skies last week.

    A bunch of observers had a look at the Deerlick group. Unfortunately, conditions weren't the best (hazy skies), and we were able to see 3 members of the group with some difficulty in a 17.5" and two members in a 12" despite the low elevation of Pegasus during the evenings of the month. The observation was made from near Karada, Coorg district, Karnataka, India.

    Regards
    Akarsh
    18" f/4.5 Obsession dob "Romela"
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  11. #11
    Member hajuem's Avatar
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    Hi Christan

    Very well observed and drawn, Christian!
    Also, the detail drawing of Ivan is great!
    The curvature of the halo comes out of it well!

    Lg of HaJü

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