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Wolfgang Hasper wrote:
> Dear all,
> many times I thought of a stopwatch that allows timing
> a sight by just freezing the digital display by push
> of a button, while, of course, the watch runs on.
> Another push of the button should then reset the
> displayed time to the actual moment...

This is the "split" function, very common on digital stopwatches.
When the stopwatch is running, you press a button to "photograph" the
time and store it in a memory. The stopwatch keeps running and does not
reset.

The "lap" function is similar, except that the watch resets to zero.
This allows you to time each lap of a race with a single watch. In the
old days you did this with two mechanical stopwatches, one in each hand.
When your car crossed the line, you started one watch and stopped the other.

I think all modern digital stopwatches combine the split and lap
functions. That is, each memory location stores both the split time and
the lap time.

My $25 Timex wristwatch has a stopwatch with split and lap functions,
but you must select one or the other. It can't do both. Also, there's no
memory. The display freezes for 10 seconds so you can read the split or
lap time, then returns to normal.

For celestial nav, a "stopclock" with a split function to store the
Greenwich time and date would be better than a stopwatch, but I've never
seen such a device, although many stopwatches display the date and time.
So, you have to 1) start the watch at a known time before beginning the
observations, or 2) start the watch at an arbitrary time, and determine
the start time later.

In either case, never stop the watch until you're satisfied with the
observations. If you suspect a mistake in the stopwatch start time, it's
easy to check -- if the watch is still running! Simply take a split on
your time standard and re-compute the start time. But if you stop the
watch, a check is impossible.


> I wonder if this awfully expensive thing (~160$) would
> at least offer what I was looking for?

"Awfully expensive" is right. I think you can get a good stopwatch for
about 1/3 or 1/4 of that price.

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