Re: Iridium flare across the lunar surface

From: Anthony Ayiomamitis (
Date: Tue Jun 12 2001 - 17:18:13 PDT

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          Thanks to Jari's message and his reference to Sat-Tracks. The two
    URL's below graphically describe my concerns described below.
    Anthony Ayiomamitis wrote:
    > Folks,
    >      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
    > flare.
    >       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).
    > Anthony.
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