Re: Bright Sat Photometry?

From: Marco Langbroek (
Date: Sat Sep 12 2009 - 23:47:25 UTC

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    One problem to tackle is that the satellites and stars don't have the same 
    angular velocity. I.e., you can't directly compare a star trail to a satellite 
    trail. Correcting for that is rather complex. Also, very bright objects (like 
    the ISS) tend to get saturated.
    As far as simply measuring pixel values in a photograph, software like MaximDL 
    can do that (that is what I use for the flare graphs).
    - Marco
    npr61 schreef:
    > Hello:
    > Are there available software that could be used for comparative 
    > photometry of a bright sat, i.e. ISS, trail?  Have been toying with the 
    > idea of buying a used Digital Rebel, fitting it with a 50mm f/1.8 lens, 
    > and then taking short, say 8-12 second unguided exposures of the ISS 
    > against brighter background stars.  Ideally, it would be nice to be able 
    > to create a rectangular aperture over all or a portion of the ISS trail, 
    > with circular apertures for the ref/check stars.
    > I've no background in this subject other than a lot of reading over the 
    > last few months. The goal would be a simple and fun way to put 
    > brightness numbers on a given pass, to perhaps the accuracy of that of a 
    > good visual observer.  Am very much considering AIP4WIN for general 
    > knowledge, but don't think that it could perform the task.  On the other 
    > hand, wrestling with something like IRAF would perhaps defeat the "fun" 
    > intent.
    > Any advice would be welcome.
    > Thanks,
    > Neal Robichaux
    > 29.9884N
    > 92.1498W
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