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Thread: I saw M31! Or did I?

  1. #1
    Join Date
    Jan 2005
    Posts
    92

    I saw M31! Or did I?

    I was excited to see that Andromeda rose so early this time of year (I only started paying attention around Jupiter or so) and I always wanted to see M31. I live in a light-polluted area (I noticed that Epsilon Cassiopeiae was just barely visible with my naked eye). I waited until about 1AM so that M31 was a bit higher in the sky. I didn't have any star chart with me, so I relied on scanning the sky with my 7x35 binoculars (I own 10x50's, but the 7x35s are more stable and have the same ratio of magnification to aperture, so I used those).

    Anyway, short story long, I knew the approximate place to start scanning and I didn't really see anything except at one point there was something in my periphery that caught my attention. I looked at it, but saw nothing. I scanned the sky a bit more, straying from that spot a little. Eventually I came back to that spot and the same thing happened. There was something there that caught my eye, and when I looked straight at it, it just wasn't there. So, I remembered learning that sometimes dim objects are easier to see when you're not looking straight at them, so I deliberately averted my vision. I am pretty dang sure that I saw it, but it was easily the dimmest object I've ever made out. I'm still second-guessing myself, but the fact that I caught it twice in the same spot, combined with the fact that Google Sky confirmed it was exactly the correct spot, makes me think that I really did see it.

    It's a shame, in a way, that I couldn't see it unless its image was projected somewhere outside my fovea, where I would have been able to see some detail, if there was any to see. I hope to be able to travel to a dark site sometime soon.

  2. #2
    Join Date
    Aug 2005
    Location
    NEOTP Atlanta, GA
    Posts
    2,746

    If it's dark enough...

    ...then M31 is visible to the naked eye. I saw it in the Chianti wine region and another time in Arizona.

    And yes, it sounds like you did see M31 using your peripheral vision. M31 covers roughly the same area as a full moon but of course is very dim.
    Last edited by schlaugh; 2007-Sep-10 at 05:51 PM. Reason: augmented response

  3. #3
    Join Date
    Sep 2003
    Posts
    4,750
    Chances are that if what you observed was a fairly large, roughly elliptical fuzzy that you indeed did see the core of M31.

    Dave Mitsky

  4. #4
    Join Date
    Aug 2003
    Posts
    1,109
    Sounds like you got it!

    You won't be able to see detail with your naked eye, even at a dark site, and it's unlikely even in 10x50 binoculars: there isn't a lot of detail to see! But at a dark, dry, dust-free site, you will get an idea of the size of the thing. The full extent is about 6 by 2 full moons (3x1 degrees), though you will probably see around half of that with small binos. The core is the brightest part; that's all we can see in our 16" Meade here in Philly! At least your sky isn't as bad as ours here...

    And it is definitely a corner of the eye thing at hazy sites. I can reliably see it when visiting my family in northern Wisconsin in the winter, and it's pretty easy with binoculars.

    Oh, the method I use for finding it (you've probably already figured this out):

    1. Find the great square of Pegasus (biggest bright near-square in the sky).
    2. North-eastern most corner star (which is also in the constellation Andromeda).
    3. Think of Andromeda as a "swooping" cone, which bends and opens toward the north, away from Pegasus.
    4. Count two pairs of stars from the corner of Pegasus (first pair close together, second pair a bit further apart).
    5. Look north of the northern star of that second pair.
    6. M31!

  5. #5
    Join Date
    Dec 2006
    Posts
    3,275
    How sad so many now live where they can't see the night sky any more. M31 is a very easy naked eye object from unpolluted skies. Even in light polluted areas, if you can see any hint of the Milky Way its core is visible to the naked eye as a fuzzy object. But in good skies it is about the size of a full moon to my eyes with direct vision and about 3 full moons with averted vision.

    Averted vision is what you discovered and allowed you to just barely glimpse its core. M33 is also naked eye from a dark site and from a really dark site with Magnitude 7 stars visible I can see M81 as well with averted vision. I may be seeing the combination of M81 and M82. Averted vision, as you discovered, doesn't see fine details. Movement also helps to see faint objects. With time you'll learn how to use them to great advantage.

    I too prefer the 7x35 binoculars for the reasons you gave. Now drive out to a dark site and really see M31 and the rest of the night sky. But don't make the common mistake of viewing from around a campfire. That does make the sky very black but only because your eye is not dark adapted. The really dark sky is gray not black as our atmosphere does glow. Viewing from a campfire so shuts down our eyes we don't begin to see this faint glow and the myrad of stars visible to a fully dark adapted eye at a truly dark site.

  6. #6
    Join Date
    Jul 2007
    Posts
    74
    Back in the ancient days of the early 80's, I had to learn where M31 was by rote.

    Find a bright star in Casseopia, move over, over, down, and over again and just 2 o clock from that.

    Frustrating, but easier than using setting circles.

    But all those years of learning where stuff was is good, even with a GPS goto scope with everything in it.

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