NavList:

   

Reply

A digital stopwatch with memories for "splits" is good for timing
observations. Start it at a known time. Take a split at each
observation. When finished with observations, add the start time to
the recorded splits to get the observation times.

If there isn't time to prepare the stopwatch, begin with it at zero.
Start it at the first observation, and take splits at the subsequent
observations. Finaly, take a split at a known time to determine when
the watch was started.

With either method, don't stop the watch until the observations are
reduced and look reasonable. If you suspect the "known time" used to
anchor the splits was a blunder, it's easy to check - if the watch is
still running.

Edmund Scientific no longer sells the stopwatch I bought, but this one
sounds like it has the same specs, except more memories:
http://scientificsonline.com/product.asp?pn=3039157

I don't think temporary exposure to the temperature on deck will
affect a quartz stopwatch's rate significantly, unless the battery is
weak. It would be easy to confirm that with an experiment.

With memories you don't need to read the watch on deck, so the display
going sluggish or dim in the cold doesn't matter.

For a small boat celestial nav "chronometer", I'd use the watch on my
wrist, with the clock function of the stopwatch for backup. Nowadays
cheap watches are very precise, and the celestial position will be
cross-checked with radio nav, so the timepiece isn't as critical as it
once was.

GPS is an obvious source for accurate time. But beware, some receivers
have been known to display grossly incorrect time, even when locked on
and giving an accurate position. I mentioned that a few months ago:

http://www.i-DEADLINK-com/lists/navigation/0309/0085.html

Fortunately, the problem seems to be restricted to a few models.

I can vouch for the Magellan 315. Mine has always been within one
second of WWV. Its sibling, the 320, would be better for marine use.

   

Reply