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Thread: I Zw 18 aka UGCA 166

  1. #1
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    I Zw 18 aka UGCA 166

    So popular in the science scene so rare observed in the amateur scene - I Zw 18?

    Last new moon period I tried this unusual young and active dwarf irregular galaxy. With the 27-inch the galaxy was visible without problems with direct vision at 586x-837x. Seeing was only average. The brighter knot was easy to detect but the fainter one (~5" distance) was tough and only pops in and out of view. I could not see the companion galaxy 30" NW.

    What are your experiences with this fuzzy guy? Could anyone catch the companion, Jimi?

    HST - ESA/STScI
    0710-022b.jpg

    SDSS (~3'x3')
    SDSS.jpg

    sketch: 27", 586x-837x, NELM 7m+, Seeing III
    Clear Skies, uwe
    http://www.deepsky-visuell.de
    Germany

    27" f/4,2

  2. #2
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    A quite faint target indeed, Uwe ! Could you give us an estimate of the visual magnitude of each component ?

  3. #3
    Member Steve Gottlieb's Avatar
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    I've viewed I Zw 18 in my 18-inch a few years ago, but it was just a very faint glow, slightly elongated NW-SE, ~20"x15", located just 0.6' west of a mag 15 star. The fainter component was not seen (or resolved) at 280x. I'm guessing the V mag of the main component is close to 16.
    Last edited by Steve Gottlieb; October 24th, 2014 at 05:46 PM.
    Steve
    24" f/3.7 Starstructure
    18" f/4.3 Starmaster
    Adventures in Deep Space
    Contributing Editor, Sky & Tel

  4. #4
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    Simbad only gived the V magnitude of the brighter component: 15.98.


    Clear skies,

    Wouter

  5. #5
    Member Howard B's Avatar
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    The SDSS DR9 tool gives a visual magnitude of ~16.5 for the brighter component and ~17.5 for the fainter. The companion galaxy is shown at magnitude ~19.7.
    Howard
    30-inch f/2.7 alt-az Newtonian
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    Contributing Editor, Sky & Telescope magazine

  6. #6
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    16-16,5vmag/17,5vmag fits into the observations of Steve an me. 19.7 looks a little bit hard for the 30-inch class.

    The object remembers me of the view of the Footprint M 1-92 through a 12-inch telescope, pretty the same knot situation.
    Clear Skies, uwe
    http://www.deepsky-visuell.de
    Germany

    27" f/4,2

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