NavList:

Thanks for your input on that. Greatly approciated

What I use for sunrise is the value I get from the Nautical Almanach for that day. I would think the value would be the exact time when the sun's altitude is 0. I know that because of refraction the sun will appear much higher but it doesn't really matter since my calculation is based on the time of sunrise from the Almanach and not from observation.

In all cases, the error is relatively small (52.0, 54.3 and 53.4). The difference between the Bowditch table and the amplitude calculation (54.3 and 53.4) seems to be the result of rounding the parameters when entering the table. Indeed, the value calculated seems to match precisely your value with Nories.

Thanks