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The same can be done with any cheap digital watch with a stopwatch 
function. They allow you to take many "lap" times just by pushing a 
button which you can read later. Reset the stopwatch and then start it 
running and write down the clock time. Then just press the "lap" button 
for each shot. At the end of all the shots simply recall the "lap times" 
from the memory and add them to the start time to establish the times of 
the shots.



gl




Brad Morris wrote on May 14, 2009:


And speaking of navigation and time....

For a very long time, I was puzzled by Dutton's recommendation to navigators 
that they obtain a split seconds watch.  He described two second hands.  One 
would continue to beat time, the other would pause and hold the time whilst 
it was recorded.  I search far and wide for a "split seconds" watch of this 
type.  I am very pleased to report to the list that such a watch should have 
the complication known as "rattrapante".  When you search on eBay for this 
type of watch, you immediately get listings describing exactly what Dutton 
recommended.

I somehow managed to obtain one.  Am I ever pleased!  The rattrapante 
chronograph I obtained holds not only the seconds, but the hours and minutes 
and tenths of a second as well. All of the hands are analog.  I have set the 
rattrapante complication to GMT, while the normal analog watch is set to my 
local time zone. Upon observation, I reach with my left hand to my right 
wrist and press the button.  Now the altitude and time correspond and can be 
recorded at leisure.

I have been carefully rating the rattrapante against the USNO time, 
(202)-762-1069 here in the US.  The rate is 0.200 seconds per day, when rated 
over the past 20 days.  Each day, the USNO time is compared to the 
rattrapante, and the resultant error is recorded.  Since the tenths of a 
second is the resolution, I should continue more than 50 days to eliminate 
any quantizing error. If the rate is not precisely 0.2 seconds, then as the 
accumulation of short or long rate continues, eventually, there will be an 
advance or retreat that holds.

I thought it relevant to report the name to others who might wish to obtain 
the watch recommended by the US Navy for celestial navigation.  Dutton, after 
all, was the text used at the Academy!

Best Regards
Brad


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