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Thread: NGC 4236 Low Surface Brightness Spiral

  1. #1
    Join Date
    Dec 2006

    NGC 4236 Low Surface Brightness Spiral

    While its listed size is smaller than M81 and it is tilted about the same angle (east to west in the frame not as seen from earth) it almost didn't fit while M81 fits without a problem. I centered on what appeared to be the center of the bright bar but it was surprisingly unsymmetrical so I ended up almost cutting off the bottom of the galaxy. It was so faint I didn't see this until I started processing it.

    How a galaxy can have so many hot blue stars and be so dim I don't quite understand. It is only 11.5 million light years distant, slightly closer than its far brighter neighbor M81. It is part of the M81 group. Some references call it "heavily obscrued" but that usually results in it being reddened. Also there are so many faint background galaxies that this obscrued idea just doesn't fly with me. They'd be obscrured as well. Look closely at the full size image and it appears there may be more galaxies in this photo than stars. I wish seeing had been better. Seems this winter if I don't have clouds seeing is lousy, the moon is bright or both.

    I'd expected to see some pink HII regions. They are quite obvious in M81. But none show up. If it isn't blue it isn't in this galaxy it would appear. More likely they are so small they are beyond my seeing and drown out by stars they've created. Quite a few individual super giant stars of 19th and 20th magnitude are visible in this image.

    I took my usual series of 4 luminosity and 2 each of RGB images but it was way too noisy so the next clear night I did it again. Due to only a small hole in trees at this high declination I can't do more in one night. Second night had a 5 day moon which certainly didn't help. Still the noise is down enough to work with. It will do for now. I have too many other objects to image if this horrid winter weather ever gives me a chance.

    14" LX 200R, L=8x10' binned 2x2, RGB=4x10 binned 3x3, STL-11000XM, Paramount ME.

    Attached Images Attached Images

  2. #2
    Join Date
    Dec 2005

    Very nice image of this spiral. The structure comes out nicely. It is interesting how little color it has.


  3. #3
    Join Date
    Dec 2006
    I can turn up the saturation but it is just blue, nothing else. Ratio of blue to green and red is small so I didn't push the saturation much. Looked rather garish blue when I tried it. So this is less saturation than I normally use.

    Last edited by RickJ; 2008-Mar-17 at 01:07 AM. Reason: Spelling

  4. #4
    Join Date
    Jul 2007
    I agree, too many sharp distant galaxies to accept an obscrued image. The entire structure seems diffuse, as if the normal gasses and dust are missing.
    A lovely picture as usual Rick.

    Kind regards

  5. #5
    Join Date
    Jan 2007
    Nice shot, this looks like an interesting, albeit monotoned subject. I'm surprised at the clear abundance of clusters, yet lack of Ha regions. I'll have to collect some exposures on it at first opportunity.


  6. #6
    Join Date
    Sep 2005
    Nice shot Rick. It is a pale one for sure.


  7. #7
    Join Date
    Sep 2005
    A Very beautiful galaxy in its class!, Many distant neighbors behind it also, Another keeper. Clear skies

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