timing technique, DRA OBS, PPAS

Walter Nissen (dk058@cleveland.Freenet.Edu)
Tue, 6 Aug 1996 14:57:38 -0400

Someone mentioned the possibility of measuring the photometric period with 
respect to events other than the maxima.  I think this is a technique that 
can be troublesome, but occasionally worthwhile.  In particular, there 
have been times when I could readily distinguish a rapid (and therefore 
precisely timable) drop in brightness, but could only poorly locate the 
very round maxima.  If the object is in a rather clear sky and near 
culmination, the "plunge" event may be more useful than the maxima.  But 
if not, then the maxima may be more useful. 
Measuring the maxima is resistant to various sources of error.  You may be 
able to accurately gauge the maxima even while an object passes behind a 
thin cloud.  The maxima may be as discernable, or more discernable, very 
near the horizon as at culmination.  In contrast, the plunge may slide 
along the light curve, i.e, be perceived at a different phase of the light 
curve, as the object rises and sets, because of variation in brightness. 
A thorough technique will allow you to maximize the amount of good data 
you can record.  If you have a watch which can record 30 or more splits 
and tape record your remarks as you observe, it will be possible to 
compute a period from the maxima, as best you can judge, and also from the 
plunges.  You can then compare these. 
I wrote at some length about the technique I use with the Casio 30-split 
wristwatch, and this was printed in Flash #102, p79.  Recently, my son 
lent me his 100-split Timex IronMan Triathlon Indiglo 721(?) B7(?) 
wristwatch.  I was not nearly as pleased as I thought I would be.  100 
splits are a lot of work, but also the watch is not nearly as convenient 
(or at least I couldn't figure how it is).  On the Casio, it takes between 
1 and 1.5 seconds to reset it.  If you recall, I like to start it about 4 
seconds prior to an even hour.  So I learned that if I merely watched the 
display until it read odd:59:58.5 and reset the watch that it would then 
be reset with the 4 second "guard time".  I also learned that if the watch 
was 6 seconds fast that I would wait until 2 seconds after odd:59:58.5, or 
even:00:00.5 to perform the reset.  The Timex apparently takes far longer 
to reset and the amount of time varies pretty dramatically with the 
history of chrono use.  It may be that this problem could be resolved by 
using the watch in a consistent way and measuring the longer reset 
interval.  But two other characteristics of the Timex turned me off. 
After an hour, it throws away the fractional seconds!  Whoa!  That's a 
tough one, forcing me to reset it just before the beginning of that 
particular hour, and worse to dump the spilts out, before the hour ends. 
Tough to do!  This isn't supposed to be a full time job.  After 100 hours 
it throws away the time altogether. 
My radically different reactions to these two watches may serve to alert 
others to make a very careful evaluation of the usefulness of various 
watches.  My apologies to anyone who tried to do with a watch similar to 
that Timex what I do with my Casio. 
Resurs 1-3 r has now become a little difficult to measure, having fairly 
round tops. 
Subtract   4.06s 
 2  4 17.64    2  4 13.58 
 2  4 36.08    2  4 32.02    18.44 
 2  4 53.62    2  4 49.56    17.54 
 2  5  8.61    2  5  4.55    14.99 
 2  5 25.42    2  5 21.36    16.81 
 2  5 40.90    2  5 36.84    15.48 
 2  5 55.87    2  5 51.81    14.97 
 2  6 14.51    2  6 10.45    18.64 
 Total  116.87  /  7  =  16.70 
   96    8  Year and month (2I5) 
   41.3735  -81.8637      256.  lat, long, hgt (3F10.0) 
    5    2    4 13.58   7  Start day,hr,mn,sec  nbr timings 
  0.00  0 
 18.44  1 
 35.98  2 
 50.97  3 
 67.78  4 
 83.26  5 
 98.23  6 
116.87  7 
Resurs 1-3 r    10.4  3.9  0.0  4.6 
1 23343U 94074  B 96214.13273442  .00000058  00000-0  95434-5 0  1813 
2 23343  97.9660 271.1237 0008746  66.1191 294.0936 14.70628624 93427 
Walter I. Nissen, Jr., CDP, dk058@cleveland.freenet.edu, 55 Barrett RD #808, 
Berea, OH 44017-1657, USA, 216-243-4980, -81d 51.823', 41d 22.413', 256m, 7x35 
94- 74 B 96-08-05  2: 4:13.6 WN   98.2 1.    6 16.37  A'A' or MM Resurs 1-3 r 
Roger Tory Peterson     -      1908-1996      -                     R.I.P. 
Remarkable Excitement   -  Remarkable Talent  -   Remarkable Contributions