Re: Lacrosse 5 with Varying Brightness

From: Bram Dorreman (
Date: Mon Aug 14 2006 - 19:54:46 EDT

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    Gerhard HOLTKAMP wrote:
    > Just observed a Lacrosse 5 (2005-016A) pass from my position at 49.8822N,
    > 8.6558E.
    > I picked it up near Psi UMa at 20:17:27 UT (13-AUG-06) at about mag 5. It
    > slowly brightened to a little less than mag 4 by the time it passed Beta UMa
    > at 20:18:21 UT. Between 20:18:33 and 20:18:50 it brightened by about half a
    > mag but I would not call this a proper flare. Then it dimmed again to below
    > mag 4 and showed a distinctly reddish color (before that it was colorless).
    > I then had to reposition my scope due to local obstacles and picked up
    > Lacrosse 5 again when it passed Gamma Cas at 20:21:05 UT by which time is was
    > slightly brighter than Gamma Cas (let's say mag 1.5). This could have been
    > part of a flare but it should have been quite bright in that part of the sky
    > anyway. Some 10 or 15 seconds after that it dimmed again rather quickly to
    > something like mag 4 or less and once again showed a reddish color. It stayed
    > like that for the rest of the pass (I followed it for another minute or so)
    > with very minute fluctuations in brightness.
    I had a similar experience on the same transit. I waited for Lacrosse
    expecting it to be bright enough so that I did not need binoculars.
    It was not bright and I picked it up when it was already between alpha
    UMa en gamma UMi. I used my stopwatch to get the times of maximum
    brightness and got the following values of time and brightness:
    20:18:50.7 mag 1.0
    20:18:56.1 mag 0.8
    20:19:17.3 mag ?
    20:19:26.5 mag ?
    20:19:35.0 mag ?
    20:19:43.7 mag 1.5
    20:19:55.2 mag 1.3
    20:20:06.0 mag 1.3
    timing accuracy: +/- 0.4 seconds
    mag accuracy: +/-0.3
    Bram Dorreman
    from COSPAR 4160:
    lat: 51.27931° N = 51° 16' 45.5"
    long: 5.47683° E = 5° 28' 36.6"
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