Re: C* 2315 r obs by Walter Nissen

Jim Varney (jvarney@mail2.quiknet.com)
Sun, 5 May 1996 10:34:15 -0700

Mike McCants wrote:

>Obs by Walter:
>>95- 32 B 96-04-18  1:38:45.2 WN  234.3 1.5  18 13.02  A'A', C* 2315 r  (??) 
>>95- 32 B 96-04-18  1:38:45.2 WN  155.7 1.5  12 12.98  A'A', C* 2315 r  (??) 
>>95- 32 B 96-04-18  1:41:35.6 WN   63.9 1.    5 12.8   A'A', C* 2315 r  (??) 
>
>Note that #1 1:38:45.2 + 234.3 = 1:42:39.5   Per 13.0 +/- 0.08
>          #2 1:38:45.2 + 155.7 = 1:41:20.9   Per 13.0 +/- 0.13
>          #3 1:41:35.6 +  63.9 = 1:42:39.5   Per 12.8 +/- 0.2
                        ^
                        ?

I'm not sure why the addition here.  The standard format for the reporting of
flash periods is that the time of the _end_ of the observation is reported.


>And start #3 1:41:35.9 - end #2 1:41:20.9 = 14.7
>
>So, #1 = #2 + 14.7 + #3.

No, obs #3 begins over one minute after the end of obs #1 and #2.

>Unless the observer thinks that the 14.7 observation is when something
>really unusual happened and that the before and after series are not
>really properly related, they should all be combined and #1 reported.

There are two choices to be made: whether to report #1 or #2, and whether
or not to report #3 at all.  The #3 obs stands alone and cannot be "combined"
with #1 or #2.

>My opinion is that nothing unusual happened and that the 13.0 period
>agrees with the rest of the world and that the longest possible accurate
>span (#1) should be reported.

Okay, since #1 and #2 have the same result = 13.0 sec.  The hundredth digit
(13.02, 12.98) should not be shown since the precision of the measurement is
not sufficient to make the hundredth digit meaningful.

>Anonymous:
>>I'd choose the middle one.  In general, my personal feeling is to avoid 
>>timing more than ten flashes [or more than 90 degrees of sky] to minimize 
>>the synodic effect.

While I may question my own identity from time to time, the post from which
you're quoting had my .sig at the end and left no doubt that I wrote it :)?

>The synodic effect is related to the apparent angular speed of the object.
>It cannot be minimized by reducing the number of flashes in order to reduce
>the actual amount of sky that the object covers while being timed.
>
>One could minimize the synodic effect by making observations when
>the object is very low in the sky and moving at a slower angular speed.

I see something of a contradiction here.  If one had to chose between two 
observations: a) horizon to culmination and b)a culmination-centered obser-
vation, would not a) have less synodic effect because some of the flash
measurements are taken when the object has a low apparent angular velocity?

I should have been more clear in my original post.  When I said I try to
limit my observations to 90 deg. of sky, I should have also added "to
either side of culmination as much as practical."

>But I would recommend against this as a deliberate act.  :-)?

Why not?  As long as the object can be clearly seen and timed, it seems like
the practice ought to be encouraged.  The only downside with observing at
low altitudes is that the neighbors might think you're spying on them or
something :)


Good Passes,

Jim


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Jim Varney      |  121^ 23' 54" W,  38^ 27' 28" N   |           Sacramento, CA
Civil Engineer  |            Elev. 31 ft.           |jvarney@mail2.quiknet.com
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