NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Paul Dolkas
Date: 2015 Nov 8, 12:29 -0800
A variation on this method, mentioned by others already, is to use the stopwatch function on a wristwatch. You start the stopwatch ahead of time at the hour (any hour will do), and use the “lap time” function to temporarily freeze the display when you get the sun/horizon alignment on the sextant. The display will give you the minutes & seconds; you just need to know the current hour. The lap timer will usually unfreeze the display after 10-15 second, or you can unfreeze it by hitting the button a second time (preferred).
I really like the “time memo” function somebody talked about on their digital watch. Unfortunately, I have only seen it on this watch, and no other.
Paul Dolkas
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of Mark Coady
Sent: Sunday, November 08, 2015 9:27 AM
To: paul@dolkas.net
Subject: [NavList] Use of stopwatch taking sights, any other users?
In plodding through Self Contained Celestial Navigation with HO 208, I stumbled on this thought process again.
IF taking sights alone, I have a habit of taking sights using a high grade mechanical stopwatch. I was wondering if others use this technique.
Simplistic enough, I start a stopwatch off the ships "chronometer", whatever it might be. I typically use a rythmic hand motion (I am a musician too, which helps) counting the ten or fifteen seconds up to a start point so my start is within fractions of a second off my record timepiece.
At this point you record your start time, and go up and take your sight. Stopping the watch with a fingertip (without looking) at the precise instant you achieve your coincidence of the body with horizon, etc.
I learned the technique from my late father long ago sailing with him. I still use his personal stopwatch on a lanyard. I believe he learned it at the USCG Acadamy.
To summarize the logic of the method:
On the plus side:
1. The most critical timepiece remains safe below and protected. With my proven ability at snapping watch bands on rigging..or finding a way to drop the one thing I don't want to....this makes a lot of sense.
2. The instant of body/horizon contact is easy to capture precisely on a moving vessel. A finger tip press captures the moment on the pass, even if a small vessel is moving excessively.
3. Farsighted, I wear reading glasses. I don't use them for the telescope or sight tube. It is hard to switch from the scope to a timepiece up close. Stopwatch button eliminates this issue, as I can put my glasses back on below where they are clean and dry. (I have also used the goofy technique of a pair of reading glasses with one lens fallen out. I discovered this one day when it actually accidently happened. I could see through the scope with the no lens side, and read close with the other eye. Not very sexy, but remarkably functional).
4. The stopwatch error based on start and stop is very minimal. Mine is easy to read to 1/10th of a second. My initiation accuracy seems to be very good.
On the down side:
1. It adds a data step. Adding stopwatch time to clock time. Adds a chance for recording error.
2. I have forgotten to write the start time. Which I always do on whole minutes.
3. Unless the stopwatch is electronic (mine is a windup), with lap timers, quick sucessive sights aren't possible if you stop the watch.
Ultimately it has good points and bad points, and you use the method when it seems to make sense.
On single sun sights, or more widely spaced noon sights bracketing the sun on the meridian for longitude, it works very well.
Any other thoughts.
