Re: Why is ISS still visible in Earth's shadow?

From: Robert Reeves (
Date: Mon May 02 2011 - 11:46:47 UTC

  • Next message: Russell Eberst: "2011MAY1-2.OBS"

    Subject: Re: Why is ISS still visible in Earth's shadow?
    > I've been thinking about this for some time. Just how bright is a city as 
    > seen from LEO? It's not an easy question since we're dealing with a light 
    > source that has a very large angular size. Then again, cities at night are 
    > popular photography targets for the ISS astronauts while photos of stars 
    > and constellations are almost non-existent. So maybe there are clues there
    Actually, the lack of true astrophotos taken from the space station is more 
    a reflection on the fact that most astronauts are not amateur astronomers 
    and are not interested in astrophotography.  And the challenges of 
    photographing the stars from an unstable (as compared to Hubble) platform in 
    Earth orbit with off-the-shelf equipment available on the station are quite 
    large.  One astronaut who is an amateur astronomer and did quite a bit of 
    astrophotgraphy, as well as the pioneering work on high-resolution city at 
    night photography, was Don Pettit on Expedition 6.
    A 10 minute video Don produced himself of his cities at night work can be 
    seen on YouTube at
    His work started an extensive database for measuring and characterizing 
    urban brightness.  I have no doubt that the night time glare of a major 
    metropolis can sufficiently illuminate the ISS to make it telescopically 
    detectable within Earth's shadow, but don't have the math to calculate the 
    expected magnitude.  I suspect it would be 8th or 9th...a challenge without 
    automated scope tracking.
    I am looking forward to his flight back to the station in November when he 
    will again continue his photography with better cameras than the clunky 
    Kodak digital they had in 2002.
    Robert Reeves            San Antonio, Texas
    Planet 26591
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