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Thread: Object of the Week - November 21st, 2016; IC 342 “The Hidden Galaxy”

  1. #1
    Join Date
    Feb 2012

    Object of the Week - November 21st, 2016; IC 342 “The Hidden Galaxy”

    IC 342 “The Hidden Galaxy”
    (UGC 2847, Caldwell 5)


    RA: 03h 46′ 48″
    DEC: +68° 05′ 44″

    Vmag: 8.4
    SB: 14.9
    Size: ~21′

    This time we visit a famous but rare observed, a luminous but visually dim and a photographic spectacular but visually tricky object – the “Hidden Galaxy IC 342”.

    The discovery last until Barnard pointed the 12-inch Refractor of the Lick Observatory to the position of IC 342 in 1890. Interestingly Denning pointed his own alt-azimuth mounted telescope – a 10-inch Reflector (already equipped with a silvered glass mirror) to the same position nearly 2 years later and made a curious double discovery. Curious because of the too late date for both – the deadline of the NGC was in 1887. Dreyer collected all later discoveries and finished a first list of the ″Index Catalogue of Nebula found in the Years 1888 to 1894, with Notes and Corrections to the New General Catalogue″, today often called ″IC 1″ in 1895 with the entry of our OOTW, IC 342.

    But why dim, visually tricky and rare observed although the very large size and total brightness? The solution is caused by the for a galaxy stupid sky position. IC 342 lies very near to the galactic plane so that dust, gas and stars dim the light of the galaxy. For example the famous Milky Way positioned ″Heard Nebula IC 1805″ is only 10° away.
    Today we know that IC 342 is member of the Maffei-Group. For ″fuzzy-ball observers″ names like Maffei I/II, Dwingeloo I/II or Cam A/B could be another target and an object-related observing program – of course with IC 342 only as a star-hop starting object . The Maffei-Group counts to the nearest group of galaxies beyond our Local Group. The somewhat difficult to define distance of IC 342 is around 10 Mlj.

    Similar but much more difficult to the large, total bright but surface faint M 101, IC 342 could be detected even with large size binoculars or a 4-inch telescope when the sky a transparent enough. The difficulty is the detection of the faint spiral arms. My experience is that the spiral structure is barely visible in mid size telescopes without showing any direct detail or arms. I could only detect individual arms with my 27-inch and a very patient observation. Interestingly some brighter portions on photographs were nor visible while some fainter regions were visible better than expected.
    But what are your experiences? Could the arms be detected even in small or mid size apertures and what are the brightest and easiest regions?

    photograph: Martin Germano, 8"

    sketch: 27", 172x, NELM 7m0+

    So Give it a Go and let us Know!
    Clear Skies, uwe

    27" f/4,2

  2. #2
    Member RolandosCY's Avatar
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    Apr 2012
    Mosfiloti, Cyprus
    A superb object. I have not yet observed it with my 18", but back in November 2009 I remember observing it under superb transparency and extremely dark skies with both my 12" dob and an 80mm ED refractor. What struck me was that I could see it more easily in the 3" refractor rather than in the 12"! If I remember correctly, the contrast of the diffuse haze (the arms) was much higher in the smaller scope. In both scopes it was visible as an ill-defined faint blob with a diffuse haze behind many foreground stars.
    The Darker the Better!
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  3. #3
    Member Ivan Maly's Avatar
    Join Date
    Dec 2012
    A most tricky object indeed, and an excellent sketch there, Uwe. Below is mine from earlier this month. 12", 75x, SQM 21.33. Not all stars plotted.

    Last edited by Ivan Maly; November 24th, 2016 at 03:13 AM. Reason: image link corrected

  4. #4
    Member Howard B's Avatar
    Join Date
    Feb 2012
    Portland, Oregon USA
    Here's an observation with my 28 inch from the Oregon Star Party a few years ago:

    IC342_crop.jpg IC342_cropinvert.jpg

    "This looks like a big faint face on spiral galaxy - lots of faint and ill-defined spiral arms are visible. Best seen at 253x but 105x is pretty good too, just less contrast." No SQM reading but I'll bet the sky was really good, especially looking at the observations of IC 10 and Maffei 1 on the same page of my notebook.

    An observation with my 20 inch in 2002, also from the OSP:
    "I could see the core as it's rather bright and small. The rest of the galaxy is so faint and patchy that it appears more like a collection of faint galaxies rather than one large galaxy, except for what seems to be the brightest spiral arm. A surprisingly challenging object. 83x - 261x."

    A 2013 observation with the 28 inch, also from OSP:
    "IC 342 got larger the more I looked at it which is why my sketch doesn't fit in its space on the previous page. Low surface brightness spiral arms wrap around the small core, which has a star like core. A ghostly galaxy for sure. 155x, 253x, 21.69 SQM. (only the core was seen at first at 131x and 155x, but the spiral arms started to be detected at 155x with averted vision. They were seen better at 253x and had more contrast right away.)"

    Bumping up the power increases the contrast of the spiral arms enough for me to see more than just the core - those arms are faint buggers!
    28 inch f/4 alt-az Newtonian

  5. #5
    Member Daniel_Sp's Avatar
    Join Date
    Feb 2012
    Münster, Germany
    Hi Uwe,
    great sketch! Even with 24" and almost 17 years experience I'm still 'afraid' of ICs, perhaps because of my bad conditions... But I really have to give IC 342 a try...

    CS, Daniel
    24"-Dobson, f/4.16

  6. #6
    Join Date
    Jun 2014
    Madrid, Spain
    My observations of Saturday night (25 Feb) from SQM 21.4 skies with excellent seeing:

    At 83x and 151x a tough object because of the low surface brightness of the galaxy and the presence of lots of fairly bright stars. The nucleus of the galaxy is stellar with a round haze around it. To the south west lies a string of fairly bright stars. To the north east and north of the nucleus (on the other side of m=11.2 star GSC 04327-1375) I see a broad spiral arm curving along the nucleus. At 83x the string of stars is embedded in nebulosity which is a second arm. To the south west of it runs another arm. North of the m=11.8 star GSC 04327-1007 (which lies due east of the nucleus) I see a small, oval patch of light.

    Clear skies, Wouter

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