Poor image of the ten last Iridiums in morning twilight

From: Björn Gimle via Seesat-l <seesat-l_at_satobs.org>
Date: Sun, 13 Jan 2019 18:01:28 +0100
 ("Astrometry.net" JPG link : http://nova.astrometry.net/image/5749384)
And the HeavenSat prediction of the tracks at the approximate time may end
up in the files folder ?

On the morning Jan.12 I had a favourable pass of the last 10 Iridiums, 14.5
h after launch. Because they were still far below nominal height, the
evening passes were in shadow at my latitude.

I copied all of the morning's images around 83 degrees in the E
onto my hard disk ( 2s at f/2.0, ISO 800, due to the morning twilight,
roughly every 10s ), and opened the image closest in time to the predicted
time for the new Iridiums.

To my surprise, THIS one contained (all 10 ?) satellites. It may look like
one track of one flashing satellite, but I have the next image, showing
most part of the same trail, shifted by less than half the length in that
8s interval.

All 10 !? That is what my prediction showed - it seems most pairs are too
close to be recognized separately as 2s long tracks - the total span is
about 11 s wide. I should have used 1s (and maybe ISO 1600) exposure to
separate several objects.

The B object (and D) has an elset epoch 5+ h after my obs, and shows B 5 s
late relative to an elset at 4+ h - being raised ??
(This earlier elset, and the remaining objects, do not have an epoch close
to the ascending node time)  And the duration of the trail would be 16 s
with these TLEs.

Björn Gimle, COSPAR 5919
59.2617 N, 18.6169 E, 51 m
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Received on Sun Jan 13 2019 - 11:02:32 UTC

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