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 bragging). 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 did. RESOLUTION - CAN ONE IMAGE AN ASTRONAUT ON THE ISS? 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 about 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 situation. 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. The 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 brighter 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 might 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 evidence 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 software 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: http://en.wikipedia.org/wiki/Canals_on_Mars COLOR OF NANOSAIL 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 be 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 that gets confused by large "black" areas or quite likely Thierry could be wrong. An experiment could settle this. Ideally I'd like to see Thierry design the 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 balance 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. LETS WORK TOGETHER 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 ideas 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 "they 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 http://gr5.org _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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