Iridium flare across the lunar surface

From: Anthony Ayiomamitis (
Date: Tue Jun 12 2001 - 15:52:31 PDT

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         I have been meaning to throw in my two cents worth in the recent
    thread on looking for Iridium flares across the lunar surface but
    somehow I have been forgetting.
         My suspicion is that this would be an exercise in futility even
    though we could be dealing with identical magnitudes between the flare
    and the crescent moon at -8 mag or so (forget about the full moon and
    the -12.7 mag). What makes the photography of the Iridium flare possible
    is that we are capturing a moving object during the 20-40 second
    exposure. As a result, we do not have overexposure but simply a nice
    image across the film.
          Now, if we were to shoot for 20-40 seconds with the moon (any
    phase during its cycle) right smack in the middle, I seriously doubt the
    quality of the resulting image since the moon exposed for 20-40 seconds
    will certainly be unrecognizable. We should be getting a very serious
    blur of the stationary moon!
          I remember taking some night time photos a few years back of the
    Chicago downtown around the lake and included the full moon within the
    field of view for esthetics. Well, my four-second exposures turned out
    beatiful images of the intended skyline, buildings etc but the moon was
    a nice blurry circle. Now imagine doing this for 20 to 40 seconds?!
          One of the challenges involved with lunar photography is the
    imaging of the one-day old moon. However, its intensity is such that it
    does not require 20 to 40 seconds and, yet, one would be forced to shoot
    for something in this interval so as to record the complete Iridium
          As much as it would be nice to have such a photo, I am willing to
    bet that the only way to accomplish such a feat is with a composite
    photo (one of the Iridium flare and a second multi-exposure of the lunar
    disk at a significantly different exposure).
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