RE: Lunar Iridium Flare #5, 4 Jan 2001

From: Matson, Robert (
Date: Thu Jan 04 2001 - 11:28:57 PST

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    Hi All,
    Ron wrote:
    > Observed #5 [Iridium lunar flare] at 08:26:11 UT on 4 Jan 2001.
    >  Iridium 7 (#24793).  The moon had set behind the mountains about 10
    > minutes earlier.
    Ron, you are the MAN!  At the rate Iridiums are failing and
    dropping out of the sky, no one is going to be able to catch
    up with you unless they're willing to do a lot of driving!
    > Magnitude perhaps 7.5 which is 0.5 magnitude brighter than predicted.
    > (of course I usually assigned a magnitude estimate uncertainty of 0.5)
    For once the satellite pointing error was in your favor
    for a lunar flare.  (Doesn't take much to get you from
    8.0 to 7.5).
    For those of you out there that have the means (telescope or
    BIG binoculars) and like trying challenging types of satellite
    observations, you should really give lunar flares a try while
    the satellites' orientations are still being maintained.  Set
    the source to Moon in IRIDFLAR, change your dimmest flare
    magnitude to around +10, and search for opportunities each
    month from 1st quarter to third quarter.
    If a good one turns up (say mag 9, or brighter if you're using
    binocs), note the exact date/time and the Iridium satellite
    producing the glint, and then run SkyMap with that satellite
    to get the precise star field location.  (Remember to turn
    off the satellite solar lighting constraint since IRIDFLAR
    only predicts lunar flares for Iridiums that aren't sunlit).
    Ron can give you more advice as to how you should set up
    your telescope, but definitely use your lowest power eyepiece.
    If you have an equatorial mount, you may also want to try
    the trick of setting the polar alignment to the azimuth 180
    degrees away from the satellite's culmination azimuth, and
    the elevation to 90 degrees minus the satellite's culmination
    elevation.  For example, if the satellite is going to
    culminate 70 degrees above the east at azimuth 85, you would
    want to polar align on azimuth 265, elevation 20.  This trick
    allows you to manually track the satellite in one axis (the
    right ascension axis, which you've transformed into the
    "along-track" axis.)
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