Re: About 58 Starlink objects recorded from the January 6 launch can now be seen on my YouTube video

From: Bill Gray via Seesat-l <seesat-l_at_satobs.org>
Date: Wed, 8 Jan 2020 20:25:15 -0500
Hi Paul,

    Thank you very much for posting this video.  I thought I'd take a
try at identifying the 'darksat' in the crowd.

    I compared the video to positions computed by the current Celestrak
TLEs.  I got most of the satellites running about a second ahead,  but
I set your location as somewhere in Carefree,  AZ;  you could easily be
one second's travel (about eight km) from the lat/lon I used.  Also,
the objects are presumably maneuvering,  and I know from experience
that fitting TLEs to moving targets is a pain.  (Never tried it with
low-flying ones on ion propulsion,  though;  a negative drag/BStar
term might do the trick.  But I digress.)

    After pattern-matching stars on the chart with those in the video,
I found that the center of your FOV is at about 10h24m, dec -38 45';
FOV is about 1.5x1 degree.  The stars visible at the start of the
video are (you may need to set fixed-spacing fonts for this chart
to make sense)

-----------------------------------
|           2          3          |
|    1                            |
|                               6 |
|                  4              |
|                                 |
|                                 |
|                                 |
|   78                            |
|                    5            |
|                                 |
|                                 |
-----------------------------------
1 = mag 8.0, HD 90868
2 = mag 7.5, HD 90725,  with a mag 9.4 just above it
3 = mag 7.0, HD 90335
4 = mag 8.4, HD 90256
5 = mag 9.0, HD 90017
6 = mag 9.5, HD 89951
7 = mag 9.3, PPM 742900 = TYC 7713 419
8 = mag 6.9, HD 90549

    Note that star 6 is a class M,  probably at least somewhat
variable.  I'd bet you don't normally get mag 9.5 stars that clearly.

    The pattern of passing Starlinks is mostly quite close to that
you'd get from looking at the TLEs.  I mostly just focussed on the
ones around the dark satellite,  and made the following identifications
(i.e.,  Starlink 1113 was passing the center of the FOV at 13:25:41).

13:25:41  1113
13:25:43  1119
13:25:47  1114
13:25:50  1084 & 1130 (DARKSAT)?
13:25:53  1098
13:25:58  1123
13:26:01  1097
13:26:07  1099
13:26:10  1104
13:26:16  1144
13:26:24  1103
13:26:31  1101

    The problem is that Darksat ought to have been between 1084
and 1098.  Instead,  you get a close pairing of satellites at
the point where 1084 went by,  and you don't see anything for
Darksat.  Everybody else is pretty much where it ought to be.

    I may be jumping to a conclusion here (always a popular form
of exercise).  But it seems to me that the 'double' at 13:25:50
in your video is 1084 and another satellite,  and I think it's
Darksat,  and I don't think it's noticeably dark (the pair
look identical).

-- Bill
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Received on Wed Jan 08 2020 - 19:26:20 UTC

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