Re: Superbird A addendum

Ron Lee (ronlee@pcisys.net)
Tue, 14 Jul 1998 18:04:21 -0600

Attached is an observation I made last year that may help 
newcomers understand what they will see.  Personally I would
not worry about making this sort of detailed observation on
your first attempt.  Just finding it and getting a time of
equal flashes to a few minute would allow others to see it after 
Rob recomputes maximum visibility times.

Ron Lee

This was my third attempt with 7x50 binoculars and my first quality
obs.  Times/dates are UT unless otherwise stated.  The satellite 
first became visible at about 02:44:52 UT on 2 Mar 97.  I observed
three 23.4 second flashes before the fainter flash was detected.

Below are the stopwatch lap number (flash number), lap time from 
previous flash and UT of Flash along with comments recorded on a
tape.  Only enough flashes are included to show justification for
later analysis of mid point.
                                                                      
Flash    Lap time       UT             Comment
10        11.72     02:47:24.6      Faint
11        11.67     02:47:36.3      Bright; Brightest yet
12        11.75     02:47:48.0      Faint
13        11.66     02:47:59.7      Bright; less than #11
14        11.70     02:48:11.4      Faint (See #15)


15        11.69     02:48:23.1      Bright, almost like #14
16        11.70     02:48:34.8      Bright, same as #16
17        11.68     02:48:46.5      Bright, a little fainter
18        11.98     02:48:58.4***   Brightest yet; bad time
19        11.44     02:49:09.9      Bright
20        11.68     02:49:21.5      Bright; same as #19
21        11.72     02:49:33.3      Bright: a little fainter
22        11.68     02:49:45.0      Bright; like #21


23        11.70     02:49:56.7      Faint
24        11.77     02:50:08.4      Bright
25        11.66     02:50:20.1      Faint
26        11.62     02:50:31.7      Bright
27        11.8      02:50:43.5      Faint; hard to see  

***  Bad time. See below for correction

Note:  I use the Faint/Bright terms to differentiate relative
brightness changes between flashes.  It is not an absolute
term!  Also, the UT times are rounded to the nearest 0.1 sec.

Analysis:   If you follow the pattern of Faint/Bright flashes as
shown in Flashes #10-14, through flashes #15-22, you will see a
discontinuity once you reach #23.   This is the phase shift
previously reported.   Using those times to define a mid point
would yield a time about 02:48:58 UT if #14 is assumed the
same brightness as #15.

This basically puts the mid point near flash #18 which I recorded
as the brightest flash (likely brighter than #11).  noting that
#18's lap period is high and #19's is low, I would subtract about
0.26 second from the recorded #18 time of 02:48:58.42 UT to get
02:48:58.16 UT (2 Mar 97) as the actual midpoint.

Accuracy of the midpoint may be off by as much as one 23.4 second
period, but I have a high confidence level in this obs and derived
midpoint.

The satellite was not observed until no longer visible since a 
Flash satellite was due at 02:54 UT, but I estimate that in my
binoculars, it was only visible for about 7 minutes.