hi Allen, sampling is 0.16 arcsec per pixel, this means that 6 pixels cover 1 arcsec. On the image, USA-186 spans about 50 pixels, at 316 km this corresponds to about 13 metres. Calsky gives 18 metres for the length of USA-186 (GlobalSecurity gives a length of 13 metres for KH-12 series), but we do not know its orientation in the image. The calculation gives a plausible result. The solar array of Lacrosse3 covers about 30 pixels (5 arcsec), at a distance of 661 km this corresponds to a length of 16 meters or 52 feet. GlobalSecurity indicates a length of 100 feet for the solar array, therefore the hypothesis is that the array is inclined by 60° towards the line of sight. X-37B covers about 30 pixels on the main axis, at 341 km this corresponds to a bit more than 8 metres, for a length announced at 8.4 metres, very close considering the uncertainties of the calculations (diffraction tends to spread objects and make their edge fuzzy, this is the reason why I wouldn't try to make the same calculations about the width of satellites, it's too small). regards At 20:09 16/06/2011, Allen Thomson wrote: > > Scale (1 arcsec) is indicated on the images. > > >Thanks much for these images. > >I've been working with the scale bars and ranges >to try to measure the size of >the objects shown, but due to the bars' smallness have some uncertainty about >the measurements. Could you tell us your >estimates of the satellites' physical >size as derived from the images, i.e., x meters long and y meters wide? Thierry Legault www.astrophoto.fr _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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