Re: Nanosail-D image

From: Marco Langbroek (marco.langbroek@wanadoo.nl)
Date: Wed Aug 17 2011 - 09:12:40 UTC

  • Next message: Russell Eberst: "2011AUG17.OBS"

    Op 16-8-2011 23:30, Mike McCants schreef:
    > There is a pretty image of a pass of NanoSail-D on the
    > web pages of Becky Ramotowski:
    >
    > http://astrobeck.com/2011/08/15/nanosail-d/
    [snip]
    > It appears to me that there is some variation in the brightness
    > of the flashes in the first half (left) of the image and that
    > there is less variation in the brightness in the right half.
    
    Mike,
    
    That could be due to saturation of the trail in the right half - I have that 
    problem with Nanosail-D during the brighter parts of it's passes - it is too 
    bright!. Basically, the signal is clipped at a pixel value near 255 and you 
    loose brightness variation that visually is very apparent but photographically 
    is clipped out.
    
    In addition, this appears to be a quite reduced version of an image that in 
    reality is much larger. Take heed there - strong reduction can mess things up, 
    as large numbers of pixels have to be averaged. This can actually even produce 
    "brightness variation" that is not there in reality but introduced by the pixel 
    interpolation during reduction!
    
    - Marco
    
    -----
    Dr Marco Langbroek  -  SatTrackCam Leiden, the Netherlands.
    e-mail: sattrackcam@wanadoo.nl
    
    Cospar 4353 (Leiden):   52.15412 N, 4.49081 E (WGS84), +0 m ASL
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    SatTrackCam: http://home.wanadoo.nl/marco.langbroek/satcam.html
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    -----
    
    
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