RE: Iridium flare across the lunar surface

From: Ulrich Beinert (
Date: Wed Jun 13 2001 - 09:59:30 PDT

  • Next message: Matson, Robert: "Off-topic: asteroid transit"

    I'd say go at this with a short-focal length scope (600-1000mm) and do it
    when the Moon is a very young (or very old) crescent. That way, you won't be
    exposing for the crescent itself (this will be very well overexposed, but
    that doesn't matter), but instead have a very nice photo of the earthshine!
    Of course, you need a mount that tracks at lunar speed, but even if it's not
    very exact, the Moon will be recognizable, along with the flare of the
    satellite passing over it. A pass like this would be very rare, though, as
    the satellite not only has to be at peak magnitude (or close to it) when
    it's in front of the moon, but it also has to occur whtn the Moon is close
    to (did I mention during twilight yet?)....
    > -----Original Message-----
    > From: Anthony Ayiomamitis []
    > Sent: Wednesday, June 13, 2001 12:53 AM
    > To:
    > Subject: Iridium flare across the lunar surface
    > 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.
    > -----------------------------------------------------------------
    > Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
    > in the SUBJECT to
    Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
    in the SUBJECT to

    This archive was generated by hypermail 2b29 : Wed Jun 13 2001 - 10:00:34 PDT