Milky Way Photograph Debate [split]

Discussion in 'Digital Photography' started by Chip NoVaMac, Jul 25, 2006.

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  1. Chip NoVaMac macrumors G3

    Chip NoVaMac

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    #1
    Sorry, but I think you are pulling our leg. A 30 sec. exposure IIRC would have left a star trail in the least. Still a nice picture.
     
  2. law guy macrumors 6502a

    law guy

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    #2
    I buy the 30 secs
    2 seconds for 500 mm
    20 for 50 mm
    he's using a 19mm.
     
  3. law guy macrumors 6502a

    law guy

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    #3
    No - the "cloud" are dense stars looking on angle into our galaxy - our galaxy is called the "milky way" but looking at it through the denseness of the spiral you see the "cloud" which is also called the "milky way". The last time I saw it clearly was 12 yrs ago out in the rural middle of Washington state.[​IMG]

    Above photograph is from space.com site

    Of course our Sun is only one of the hundreds of billions of stars (400 billion give or take 200 billion is the number I've seen) in just the Milky Way galaxy. Combine that with the billions of other galaxies and looking out into space becomes fascinating quickly. The attached image below is from a Hubble deep field view - those aren't starts - those are whole galaxies (10,000 or so) of billions of stars each!!! That image is just looking in one small spot in the sky out from Earth, so multiply this out from the Earth in every direction and - wow. This image looks billions of years back in time. I digress - back to picture of the day...
     

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  4. andiwm2003 macrumors 601

    andiwm2003

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    #4
    i thought startrails are only above 1 minute with zoom. IMHO with a 19mm you don't see them after 30sec. nice shot anyway.

    last time i saw something remotely similar was when I was camping at Yosemite at ~10 000 foot elevation. i wish i had a camera or telescope then.
     
  5. andiwm2003 macrumors 601

    andiwm2003

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    #5

    compared to his yours looks upside down! gee, somebody is facing the wrong way here!;)
     
  6. seenew macrumors 68000

    seenew

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    #6
    Thanks for the lesson, haha. I know what our galaxy looks like, I just was not aware it was that easily visible from the ground, with this kind of equipment. Like Chip said, I would have expected star trails, but then again, I had to leave my shutter open for literally ten minutes to get inch-long trails last time I tried. I guess 3 seconds wouldn't show it too much..

    That reminds me, I haven't tried anything like this with my new 350D..
     
  7. pdpfilms macrumors 68020

    pdpfilms

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    #7
    I don't believe it. There's no way one could see THAT many stars, especially with a light source like a candle in the frame. A multiple-frame overlay, perhaps?
     
  8. Mr. Anderson Moderator emeritus

    Mr. Anderson

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    #8

    But he's south of the equator - so its fine :D

    D
     
  9. -hh macrumors 68020

    -hh

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    #9
    Milky Way - Explanations

    Okay, a couple of explanations.

    First off, this is a Real shot and a single exposed image.

    Next, it was really a 30 second exposure. To my eye looking at the full sized (8MP) original, it does have a little bit of fuzziness due to star movement, but the angular change was very small given that it was a 19mm lens. The sharpening probably helped some too, as did likely also the Photoshop downsampling from an 8MP original.


    For a contrasting example, here's another 30sec exposure taken the next night with my other lens for that trip, my 70-200 f/2.8 IS. The EXIF data here says 73mm @ f2.8 @ ISO 1600 @ 30sec and you can easily see the star movement trails:

    The full frame (but downsized) image:
    [​IMG]

    A crop out of the above frame to 100% pixels:
    [​IMG]

    FWIW, both of the above are "zero'ed out" RAW conversions - no adjustments.

    If I apply the same RAW conversions and unsharp mask, the 100% crop would become the following (sorry, I grabbed a different part of the frame):
    [​IMG]


    Needless to say, I don't consider this shot, regardless of how it could be processed, to be a "keeper". It is revealing in just how much the tungsten color setting affects the perceived colors.


    Back to yesterday's shot, its brightness despite the apparent lack of star trails was IMO definitely helped with its post processing. The main thing I referring to here is the +1.5 on the exposure, which if I recall my camera physics correctly means that the effective light gathering would have been improved by +1.5 stops.

    This means that the light gathering is equivalent to a (30sec)(1+1.5) = 90sec exposure. Given also that the camera was cranked to ISO 1600, the equivalent shutter times for slower ISO's would have been:

    30sec --> 60sec @ ISO 800 --> 120sec @ ISO 400 ... 480sec @ ISO 100 (8 minutes)

    or considering the +1.5 exposure post-processing contribution:

    90sec --> 180sec @ ISO 800 --> 360sec @ ISO 400 ... 1440sec @ ISO 100 (24 minutes)


    Finally, a very good comment, because it gets us into a different topic:
    We talk a lot about image manipulation these days, mostly because it has become easier to do with digital. What we tend to conveniently ignore is that the human eye is an amazing device, and the camera is sometimes a very poor substitute.

    As I want to apply that comment here, we talk frequently about a camera/film systems "Dynamic Range", which is its ability to capture the dynamic range within an image. With digital, we're doing overlays and other exposure tricks to try to make our hardware effectively have a broader range, in an attempt to more faithfully reproduce what we saw when we were there: this is all an attempt to make the camera more closely reproduce what we saw with our eye, but unlike our eye, the camera's f/stop can't instantly change as it pans within a scene.

    The human eye can adapt to six full orders of magnitude (roughly 0.1 lux to 100,000 lux), although I don't know how quickly it adapts "instantly" while we purview a scene. As such, while I'm sure that the light pollution from the candle inside our banda did wash out some of my view of the stars from right at that location, our view of the stars and the milky way on our walk back and before we lit the candle (to go find the camera gear) did roughly appear to be this dramatic.

    From a purist point of view, I may have pumped up this shot by a half, or maybe a full stop, but in balance, since I allowed the banda light to become overexposed, this is nothing that a longer shutter exposure - - and/or good old fashioned "push processing" on film - - would not have also accomplished.


    All in all, I'm downright amazed at how far the dSLR technology has come in making a shot like this so relatively easy to take.


    And next up for me is to digitize a 35mm slide where I purposefully used "chimping" on the dSLR to figure out the sunset exposure settings I wanted for the desired image on the 35mm Velvia. Hopefully I'll have that task done by this weekend.


    -hh
     
  10. Josh macrumors 68000

    Josh

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    #10
    Cool image, but it isn't real.

    For one, Earth is inside the Milky Way, and the only way to capture it as you say you've done is to be from an angle outside of it.

    Being inside of the galaxy, all you're going to see looking out is a thin band, nothing like your photoshob job.

    Secondly, the only galaxy one might see in a similar light as the one above is Andromeda which is often confused for the Milky Way.

    The problem however is that Andromeda is only visable from the Northern Hemisphere - a place where Tanzania is not located.

    Nice try, though.
     
  11. gauchogolfer macrumors 603

    gauchogolfer

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    #11
    Well, here's a picture taken from the Cerro Tololo Observatory in Chile of the Milky Way:

    [​IMG]
    This shows that it's obviously possible to take such a picture from Earth.

    Whether the poster did or not we won't necessarily know, but I'll give them the benefit of the doubt, for now.
     
  12. andiwm2003 macrumors 601

    andiwm2003

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    #12

    :confused: then all the tousands of astronomic pic's over the last 100 years are fake? :confused:

    and when i see the milkyway band in the sky (although not a s clear with naked eyes) then i'm obviously drunk?:confused:


    can we have an astronomer comment on that please?


    e.g.: http://skychasers.net/
     
  13. gekko513 macrumors 603

    gekko513

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    #13
    I think the pic gauchogolfer posted says it all, really. Josh doesn't know his stuff in this case.
     
  14. Josh macrumors 68000

    Josh

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    #14
    There's quite a difference in an observatory and taking pics out in the open with a dSLR.

    I'm also very glad you posted that pic. Unless anyone means to say hh took the photo from the very same location, at the very same zoom, at the very same angle, at the very same time of year, and at the very same time at night :)

    Overlap the one you posted, flip horizontally, vertically, and what do you know - same stars in the very same same positions, at the very same angle. Stars change angles, positions, size (apparent) and distances from one another over time - it happens in a matter of minutes as the Earth rotates. Unless he defied every bit of mathematical probabiltiy in the universe, what you're looking at is much more than pure coincidence...

    [​IMG]

    Myth = busted.
     
  15. gauchogolfer macrumors 603

    gauchogolfer

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    #15
    FWIW, these were taken with a D70 and posted on the space.com website.

    The point, though, is that the Milky Way is much more than just a "thin band" without any kind of "photoshop job".

    It's not like these are from Hubble or Cassini.

    Let's agree that such pictures are certainly possible, even common, and accessible for anyone in either hemisphere who's far enough from light noise.
     
  16. gekko513 macrumors 603

    gekko513

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    #16
    Uh, no they don't. The stars stay pretty much in the same place for years when looked at from earth. Also, the distances are so vast that it doesn't really matter much where on the earth you are or where on it's yearly travel around the sun the earth is. As long as the horizon doesn't get in the way, you should see the same stars in the same relative position from anywhere on earth. From the northern hemisphere you can't see the same as from the southern hemisphere obviously. The only things that seem to move from our small perspective here on earth are the moon, the sun, the planets, comets and asteroids. The stars stay pretty much put.

    Yeah, I know I should probably just have let it go, but such misinformation can't go undisputed.
     
  17. pdpfilms macrumors 68020

    pdpfilms

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    #17
    Why would he have to have been at the very same location at the very same zoom, at the very same angle, and at the very same time of night?

    It's quite obvious that he wasn't, otherwise you wouldn't have to flip (twice), rotate, move, and resize the space photo to match his. If (like you claim he would have to be) he was at that same spot/time/angle/etc, the pictures would be identical, aside from exposure. They're not.

    So you overlayed a stock photo of the milky way and it matched up. I'm not surprised in the least... are you trying to say from a day to day (or even month to month) basis, that the milky way changes enough so that two pictures will not be overlayable? I bet if you took the first ever photograph of the Milky way (that section of it, at least), and layered it over this photo it would match up. In fact, if anyone wants to do this- take the image overlay that Josh created, and try overlaying a third milky way photo... I can almost guarantee they would align.

    As much as my gut tells me this photo doesn't look right, it seems to check out.
     
  18. Josh macrumors 68000

    Josh

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    #18
    Uh, yeah, they do.

    The stars do not remain in the same positions relative to earth through all time. Their positions' change based on time of year and the time of the day.

    Before you "dispute misinformation," you might want to take care of your own.

    http://www.onr.navy.mil/focus/spacesciences/observingsky/sun2.htm
    http://www.astronomynotes.com/nakedeye/s6.htm

    -----------
    It's not that the two images look similar, it's the fact that the stars are the same size, shape, in the same positions, and are the same distances from one another in both photos.

    Read the links above, especially the second one in detail, and you will understand the significance of that. It is scientifically improbable that photos of the sky, from two different locations, at two different times of the day, during different seasons, would show the very same stars ligning up with such precision and accuracy.

    It's an obvious photoshop job and if common logic doesn't point that out, science and math will and they just have.
     
  19. gekko513 macrumors 603

    gekko513

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    #19
    I said their relative position, not their position relative to the horizon as observed from the earth. You'll also notice that the reason why you see different stars throughout the year, it's because the sun prevents you from seing stars during the day. If you could see through the sun, the stars would still be there and in the same relative position as observed from the earth.

    Simply put, as long as you can see the big dipper, it looks the same, anywhere on earth and any time of year.
     
  20. Josh macrumors 68000

    Josh

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    #20
    Their position, relative to their origin, other stars, and the earth (ie: an observer looking up at them), all change. At no moment are stars stationary. They have orbits of their own, each one independent of one another.

    And no, it will not remain the same. The big dipper or any other formation will change over the night and extremely over the seasons (winter and summer being the extremes). The stars that form them change positions relative to an earth-based observer. You can expect to see a similar formation through one night or one season, but different hemispheres and different times at different seasons will see it drastically different.

    Read the links I showed you - I'm not going to dispute such an indisputable fact.
     
  21. gekko513 macrumors 603

    gekko513

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    #21
    I did. They confirm what I'm saying.
    The stars stay in place and all these other things are just to figure out when and where we're able to see the different parts of the sky.
     
  22. Rower_CPU Moderator emeritus

    Rower_CPU

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    #22
    Constellations change "extremely" over the seasons? Might want to tell the Ancient Greeks that...

    It is a fact that stars are in motion, but the extreme distances make any perception of that motion here on earth detectable only with powerful equipment. To the naked eye, the Milky Way, constellations, etc. will appear almost identical from anywhere they are visible, regardless of the time of night. Their positions in the sky as it "rotates" overhead is all that changes.

    On topic: Great shots, everyone! I'm really impressed by the range of talent we've got on display here.
     
  23. Josh macrumors 68000

    Josh

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    #23
    Sorry, but no you did not. That second article will take you a while to (fully) read. You posted mere minutes (like 10) after I posted it. Secondly, they don't come close to confirming the stuff your spouting. They claim the exact opposite: stars, at different times of day and season, will be observed at different positions - and their positions relative to another (constellations) will change over seasons.

    Lying surely won't prove you correct.

    I repeat, the stars do not stay in place. See numerous request above to (seriously this time) read the article.

    You cannot walk out in your backyard in August, take a picture of the big dipper, wait until February, take another picture, and expect to see the same thing.

    http://www.onr.navy.mil/focus/spacesciences/observingsky/constellations5.htm
     
  24. gekko513 macrumors 603

    gekko513

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    #24
    Are you joking or what? It was 19 minutes between the time you posted the link and the post where I said I read them. And it takes perhaps two to four minutes to scan the article, discover that they talk about two different ways of positioning stars, one that describes the position using the altitude above the horizon and compass angle, and another that uses a fixed polar coordinate system that the earth moves within.

    Edit: I don't know how to explain so that you understand. Imagine that you're a moth circling around a lamp post on Long Island. Sometimes you see the New York city skyline, sometimes you don't because you're heading the other way or because the lamp post is in the way, but any time you see the city skyline it looks the same. It doesn't matter how much manouvering you do within 2 metres of the lamp post, the city skyline looks exactly the same. If you fly upside down, the skyline will look different, but if you rotate it in photoshop (or in your mind) you will discover that it's in fact the same skyline. No buildings are rearranged, no new towers hide other towers, no change at all as far as the moth is concerned.
     
  25. Rower_CPU Moderator emeritus

    Rower_CPU

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    #25
    Your understanding of this is fundamentally flawed, Josh. The seasonal changes are due to where the sun is in relation to these groups of stars as the Earth travels through its orbit. The section of the sky we see is somewhat different, not the relative location of the stars themselves.

    gekko's analogy of the moth, lamplight and skyline is a good one to understand what's going on. The distances we're talking about (light years) and the distance the Earth travels in its orbit (approx. 300 million KM) do not allow for any discernable parallax shift.
     
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