bright double flashes, timing procedure

Walter Nissen (dk058@cleveland.Freenet.Edu)
Tue, 25 Jun 1996 10:04:54 -0400

I'm breaking this message, somewhat awkwardly, into two parts.  The second 
part will be data intensive.  This part may leave you feeling a few gaps 
without the data. 
I previously asked this question and got no response: 
Has anyone seen bright, very rapid, double flashes from NOAA 7?  Or other 
After seeing the remarkable, extremely bright, rapid, double flashes that 
I reported for 960529, I have been trying to keep watch on NOAA 7 thru the 
occasional breaks in the clouds here.  For some weeks I was unable to see 
those double Fs again.  Mostly I have seen a very irregular pattern which 
displays repeated bright Fs and many secondary maxima which vary in 
brightness and also perhaps in time.  But 960624 I caught the object early in 
its rise and dedicated myself to timing only the bright Fs.  Consequently I 
was able to follow the object for a considerably long period and time all (but 
one of) the bright Fs over the entire period.  I also observed the rapid 
double Fs for a short while.  Again, they were so rapid I was unable to time 
the second of each pair in the double Fs.  In some ways this object is now 
quite reminiscent of the behavior of the spectacular, irregular flashers 
C* 1933 = 88- 20 A = 18958, C* 1953 = 88- 50 A = 19210, SROSS-C2 = 94- 27 A = 
23099, and DMSP F3 = 78- 42 A = 10820 when they were at their most irregular. 
Upon analysis of the recorded timings, the Fs are seen to come very regularly. 
I am not sure everyone would reduce the data shown below in the same way, 
but it appears that a case can be made from this data that this object is 
spinning up (the vagaries of the English language are such that this means 
the same as, and confirms, the comment in the March-April Satorama "is 
probably going down a bit").  Most of the timings are of bright sharp Fs, 
but not all. 
Does anyone think there is evidence for a slight asymmetry within a 7.4s 
But besides any acceleration or any asymmetry, the appearance may vary from 
day to day or week to week or even within the same pass.  On 960529 the bright 
Fs were separated by only perhaps 1/6 of a second and were too rapid to be 
timed separately.  On 960606 the bright Fs were about .8s apart or a little 
more.  On 960611, they were mostly about 3.7 seconds apart.  On 960624 a whole 
variety of behavior was seen at different times. 
I will make a few comments about my timing procedure.  I try to reset the 
stopwatch part of my wristwatch, a Casio Digi Graph 100M [828] DGW-30, 
about 4 seconds prior to an even hour UT.  E.g., I might try to reset it 
at 015956.0.  This means that if I want to find an object at a particular 
skymark at particular time, I can look at the stopwatch until it shows the 
appropriate time, ignoring any multiples of 2 hrs, and then have 4 seconds 
to lift my binoculars to the appropriate place.  I make no attempt to set 
it precisely, nor do I fret as it drifts a bit while I am waiting for my 
cloud filter to kick in.  Presently, it slews about .70 seconds per day. 
I make whatever timings of events I can (the watch stores the first 29 
splits plus the last split) and then take additional splits while 
listening to WWV or USNO telephone time.  In the morning, typically, I 
wait until WWV 15 MHz starts getting thru fairly well.  Then I wait until 
the beginning of the long tone at the beginning of the next minute.  This 
split usually reads about .2 or .25 seconds greater than the actual 
offset.  I can confirm this, more or less, from the 60-component LCD 
display which lights progressively each second, but which is not 
calibrated well enough to get me to use it in preference to the splits.  I 
now have the offset, typically, to within about .1 or .2 seconds.  I then 
take an additional split attempting to match the beep from the watch to 
the tick from the time source.  This gives me the hundredths of seconds. 
Since I am a perfectionist I then take additional splits to try to get a 
better audio match.  I seldom change the first one by more than .02 
seconds.  For some reason, the later splits seem to be more scattered than 
the first, as if some sort of fatigue were setting in. 
I then adjust the offset to account for the .7s per day slew of the watch. 
This adjusted offset is then subtracted from the recorded splits to obtain 
the UTC which I then report.  The slew adjustment varies from time to time 
as the crystal in the watch ages, running faster and faster with time, but 
this process is very slow in the early decades after manufacture of the 
crystal (and maybe later, I don't know). 
The slew adjustment is built into the little program I use to generate the 
DRA format from the raw data.  This program, of which I have written 
before, accepts an abbreviated list of the split times, which I have first 
written on paper while in recall mode on the stopwatch, the offset 
measured as above, and the date.  It then directly generates the DRA 
output which I have reproduced in many messages here and show in the next 
message.  After I prepare the data for the program, I verify that it 
corresponds to the written splits, etc.  After running the program, I 
double check the written splits one more time against the DRA output. 
If you live in the DC area and can make a local call to USNO time at 
202-653-1800, you can count on a short-delay connection, making a useful 
reference for all manual timing work.  If you live in the Ft. Collins 
area, similar comments apply to WWV at 303-499-7111.  If you use a 
long-distance connection, the delay may be longer, possibly several tenths 
of a second.  Local telephone time in the US is truly horrible, possibly 
off by more than a minute, and more typically oscillating back-and-forth 
by up to 6 seconds either way with the electric power grid.  AT&T 
guarantees a short-delay connection to 1-900-410-TIME at USNO.  WWV 2.5, 
5, 10, 15 and 20 MHz are useful, as well as the various other national 
time services.  People in the northeastern US often use CHU. 
Walter Nissen                  
Power corrupts.  Absolute power corrupts absolutely.   Lord Acton