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On glasses: One lens glasses are a great idea, and I was going to try one contact lens for sailing. One problem for me is that my glasses have a prism to correct a squint (vertical strabismus) . When I take them off it takes a few second of my brain deciding which of the misaligned eyes to use and then shuts down the image from the other one where they ovelap, and while I am aware of this I cannot control it. So I think switching from the sextant eye to the clock reading eye might take too long. With a bit of practice and opening only one eye at once I might get it to work. Of course if I didnt have central supression I would have a sextant view of the world all the time!

I wrote this reply a while ago on stop watch devices. I got a network error from the web site

I had thought of using a "random programable hand held device" and it is easy enough to make a script that runs on a (cheap) spartphone very old PDA or as you say reasonable programable calculator to do the job. I think Paul Lutus http://arachnoid.com rigged up a hand held button (could be on a serial line or use a mouse button or slide presentation clicker etc) to his navigation computer.

I just wanted something watch sized and self contained. I suppose if I have to make something it is going to cost money (and time but could be fun and learn something) but I felt sure there is something cheap out there that already does the job.

Paula from astopwatch recomended the Copilote Rally Watch.

http://www.astopwatch.co.uk/rallywatches/products.asp

That is £99 (GBP) and it is a family of watches used by rally co-drivers, so interestingly they have a need for such a facility "freeze time of day". I think one problem is that many of the cheaper stop watches on ebay designed for various motor sports including rally copilots might have this feature but the description of the product on line is not detailed enough. The cheapest watch on astopwatch.co.uk that the web site says has this feature is £41.20 (not sure why Paula didnt spot that). From this web site http://www.proswimwear.co.uk/fast-time-14-waterproof-500-memory-stop-watch.html it says that it is waterproof and records "segments" with a date and time stamp, so if that can be done with one press of a button maybe that is a good choice. Cheapest price I can find for that is £34.00 - the price of a cheap digital watch so that might be ideal. There is a video here https://www.athleteshop.co.uk/fast... that seems to show you use it like a standard lap timer, then switch to "data mode" and it has recorded the time of day. It is not ideal as the work flow I wanted was press the button with your thumb, read the sextant, read the watch, write down both, repeat. Whereas this you need a few button presses to retrieve the time so would probably write down the lap time with the sextant reading then go back to the series and write down the time of day when you had done a group of readings.

Maybe Paula was right and the Copilote watch does a better job.