Re: CZ-4C DEB 36417 Flares while in shadow - is this common ?

From: Björn Gimle (
Date: Sat Sep 15 2012 - 12:31:23 UTC

  • Next message: Peter Wakelin: "SATOBS 2012 September 14"

    2012/9/14 George Herbert <>
    > >  Also , did a search of Seesat's archives (thanks George) and only 1 hit
    > from 53 weeks ago by
    > > Kevin Fetter ,
    > although Satflares newly
    > > expanded DB showed this report by Brad Young early this year also .
    > >
    > >
    > Question - does the database show it in umbra or penumbra at that point?
    > The sun's not a point source, and this could be where a simplification
    > is getting that point wrong...
    To my knowledge, no formal reports contain info on penumbra.
    Many years ago I made comparisons of shadow entry/exit positions by some
    satellite prediction programs.
    There were large differences, not only caused by selecting umbra/penumbra
    Rob Matson's SkyMap was the most compatible with reality, and also shows
    the penumbral part in a different colour.
    Previously on the same thread :
    Flares/flashes by the Moon (and penumbra!) share the characteristics of
    solar flashes, since the Moon is roughly the same size.
    But even the full moon is about 15 magnitudes fainter than the Sun, so its
    flashes are at most magnitude +7 ! And at the time, the Moon was far from
    Planets is a different case - when we see a solar flash from e.g. an
    Iridium panel of 1.5 sq.m. at 1500 km range we see a part of the Sun. Its
    apparent diameter is 32', Jupiter 41" and Venus now 18".
    The flat apparent Sun disk at this range is 1500000m/110 diameter, about
    13500 m, ie a surface of 150000 000 sq.m.
    This ratio (if the reflection is specular and 100% albedo) makes the flash
    about 20.0 magnitudes fainter than the Sun.
    But for Jupiter and Venus we would see a larger percentage of their disk
    reflected, giving a magnitude loss of about 11.7 and 10.0 magnitudes - now
    to +9.5 and +6.0. It might be possible to see them, but the width of the
    flare track, corresponding to the solar flare 13500 m at this range would
    correspondingly smaller, much smaller then the orientation accuracy of an
    Iridium, and of course completely unpredictable for debris.
    Björn Gimle, COSPAR 5919
    59.2576 N, 18.6172 E, 23 m
    Phone: +46 (0)8 571 43 312
    Mobile: +46 (0) 704 385 486
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