one more re: resoluton of observable objects, camera color balance, observing satellites is fun (or maybe just addictive)

From: Richard Crisp (
Date: Sun May 29 2011 - 13:42:36 UTC

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    and a nice poster summarizing methods in use
    -----Original Message----- 
    From: Thierry Legault
    Sent: Saturday, May 28, 2011 10:59 PM
    Subject: Re: resoluton of observable objects, camera color balance,observing 
    satellites is fun (or maybe just addictive)
    George, Robert,
    I agree that for any conclusion about the colors on an image, the
    camera/sensor must be calibrated in precise conditions. All the more
    that, in this case, nothing can explain a blue color: neither the
    sail itself (it's aluminum that reflects the white light of the Sun),
    nor the Earth since the satellite sees the dark side of the Earth, as
    I demonstrated in my analysis page.
    The case of an astronaut is something else. I know the subject quite
    well about the detection of details smaller than the "resolution limit" 
    - I have written, as soon as 1999, a page explaining that in certain
    conditions, details under the "resolution limit" can be obtained: . These explanations are also
    available in my book about astrophotography.
    - I have made in February a full 3D video of a passage of the ISS,
    showing not only the astronaut but also the robotic arm and even the
    joints of the arm: . I'm
    also probably the first amateur to have imaged the Encke division on
    Saturn, whose width is 0.05 arcsec.
    So, of course the question is not: is it possible to image an
    astronaut? The question is: do Ralf Vandebergh's images show an
    astronaut? Initially, my comments about my doubts concerned this image:
    In this image, I see only something that may be noise, turbulence
    distortions and/or reflection of the Sun on any close element of the
    ISS. We must not forget that, if indeed the detection of an astronaut
    is possible, the fuzzier the image, the more difficult it is because
    of the very small size of the astronaut. Beyond a limit, the
    astronaut disappears, as faint stars disappear on a deep-sky image
    made fuzzy by turbulence or defocus. The resolution of this image is
    clearly not sufficient to show an astronaut, the solar panels are not
    even rectangular as they should be and much bigger ISS structures
    than an astronaut are not visible at all.
    About his more recent images, I made the same comment, and I maintain
    it, about the last image of the page (first image to be published): . For the other image, I agree that
    there is a patch of light that could be the block represented by the
    astronaut and the arm. In any case, the overall resolution is
    absolutely not sufficient to separate them (and, of course, not
    sufficient to identify the "helmet" as it is suggested in the
    caption!): the radiators show very distorted structures, far from
    what they should look like (they are composed of rectangular
    elements, as chocolate bar). The problem here, again, is that we
    haven't seen the raw images, we do not know the processing applied
    and how the raw image has been transformed. We do not know if other
    images of the video can give a confirmation or not. As I already
    demonstrated with this image of Vega that looks like a Soyuz, picking
    up one image in a video proves nothing:
    So, the patch of light could be the astronaut+arm. Or not. We can't
    say with certitude without additional information.
    best regards
    At 19:23 28/05/2011, George Roberts wrote:
    >The goal here by everyone including Thierry and Ralph isn't to whine,
    >complain, belittle, show off, brag, lie, or deceive (well maybe a little
    >The goal here is to observe satellites, share observations, and try to draw
    >conclusions from those observations.  When Ted asks y'all to share more
    >please don't get mad, you don't have to share but we would love it if you
    >For example I've been tempted to discuss Thierry's conclusion of resolution
    >limits and the ability to see something 2 meters tall using Ralph's
    >equipment (an astronaut).
    >Although I partly agree with Thierry's points I think he has a
    >misunderstanding.  That white spot on Ralph's image indeed might  (might!)
    >be an astronaut.  Thierry hasn't yet convinced me otherwise despite his
    >educational composite of an astronaut to scale against the ISS.
    >I think a simple example will illustrate my point.
    >Currently Ralph's equipment is insufficient to image the Lunar Modules left
    >behind by Apollo missions on the moon (hopefully this will change, lol!).
    >There is a commonly used equation from Rayleigh that draws conclusions 
    >resolution that only needs to take into account aperture.  I beleive this
    >formula was originally co-opted for the specific case of observing binary
    >stars of equal brightness.  The formula  doesn't necessarily apply to this
    >If I put a laser next to that lunar module, make it bright enough (maybe a
    >million watts? a billion?) and shine it back at Ralph's telescope, Ralph
    >will see a tiny dot on the moon.  That dot should be the size of a star or
    >airy disk image of a point source.  So clearly it is possible to image
    >something "beyond the possible resolution" of a given set of equipment. 
    >key here is contrast.  The object imaged needs to be so bright that even if
    >it is only one inch across on the surface of the moon, it is brighter than
    >all the reflected light from the portion of the moon at Ralph's equipment's
    >"imaging limit".  So if for example the limiting resolution on the moon is
    >an area 1 mile across, then the laser needs to noticeably brighten 1 square
    >mile of lit up moon as seen from the earth.  In the shadowed part of the
    >moon, the energy needed is much less.
    >Similarly, an astronaut working on the ISS, if lit up significantly 
    >than the area around him (sunlit astronaut, midnight dark stuff around him)
    >might be visible even if he is beyond the resolution limit of Ralph's
    >equipment.  Now the shape of that astronaut is probably noise, but one 
    >be correct in guessing that a certain region of the image is a particular
    >astronaut (or it might be a nearby part of the ISS also in bright sunlight
    >or it might be both objects merged into one).  Careful analysis of the 3D
    >shape of the ISS, the position of the arm and astronaut, and how sunlight
    >would fall on different parts of these objects might provide strong 
    >one way or the other.  Ralph did some of this analysis.  I don't think
    >Thierry did.  I'd love to see someone create a 3D model of the ISS and then
    >put a light source exactly the same angle as when Ralph photographed it and
    >then look at it from the angle Ralph did.  But this is a ton of work.  I
    >don't know if anyone will ever do this although I've heard there is 
    >that does this already.  One would need to know within a few seconds when
    >the image was taken and where Ralph was.  Ralph only included the time to
    >the nearest minute but that might be good enough as you can probably infer
    >the time and light angle by comparing 3D model lighting with Ralph's image
    >if you have software that allows you to quickly change the light source
    >position and see results in real time.
    >But we have to be careful about the "canals on mars" phenomena which fooled
    >some very smart people!  Like Percival Lowell:
    >Regarding the color of the nanosail, Thierry makes some okay and some not
    >okay points.  I'm particularly interested in this claim about color balance
    >for certain cameras in low light conditions and I would think Ralph would 
    >delighted to do a few controlled tests.  If someone accused my photos of
    >having bad color balance I wouldn't get pissed off at the person, I would
    >thank them (yes, really - I've learned to thank people for advice although
    >when I was younger...) and asked that person to help me set up some
    >experiments.  If one used the same camera indoors at night - light up some
    >very very small angular objects with a very dark background in a room.  See
    >if the camera gets it's color balance out of wack or if it indeed has just
    >as good color balance with dark backgrounds as with light backgrounds.
    >There might be some auto color balance setting (software) in the camera 
    >gets confused by large "black" areas or quite likely Thierry could be 
    >An experiment could settle this.  Ideally I'd like to see Thierry design 
    >experiments and Ralph do them over and over until Thierry is satisfied that
    >Ralph's images don't have color error introduced by the camera color 
    >or Ralph finds a setting on his camera that disables color correction.
    >Ralph and Thierry should be best friends excited on working on this project
    >together!  Even if only by phone and email.
    >I think Thierry and Ralph are contributing great stuff here and I wish
    >people would bask in this great, interesting jumble of thoughts and
    >experiments and results and not feel personally attacked.  We are talking
    >about *ideas* here.  We aren't rooting for teams like in sports.  With 
    >the best and correct idea *always* wins.  And all the people win also.  We
    >all lose if Thierry claims the pictuers are bad and Ralph replies with 
    >speak for themselves".  In that case I don't learn much.  Ralph and Thierry
    >aren't fighting each other.  Or they shouldn't think of it that way.  They
    >just have a disagreement about conclusions.  Thierry would like to see more
    >data.  Ralph doesn't want to supply it.  Regardless I think Thierry brings
    >up interesting points, some right and some wrong.  And Ralph also brings up
    >some interesting points - especially the concept that it might be possible
    >to photograph something as small as a human on the ISS.  What an amazing
    >feat if this really is possible!  It's great to try to push our technology
    >to new limits.
    >- George Roberts
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    Thierry Legault
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