Somebody gave me a book called 'Latitude Hooks and Azimuth Rings' by
Dennis Fischer publisher International
Marine. In it he describes several old instruments and gives
directions for making them. Included is a device
called a Nocturnal. The Nocturnal came in many forms, the one
Fischer describes is useful for...
determining local time by observing the position of Ursa Major (or
Minor) with respect to Polaris
determining the correction to be applied to the height of Polaris
to determine latitude again by
observing the position of Ursa Major (or Minor) with respect to
Polaris.
calculating the position of the moon given the local time, date,
and day of lunar month. Useful for predicting
local high and low tides times. EG. When should I leave port
on a given date to sail on the falling
tide.
I made one and its actually quite good at determining local time, it's
easy to come within 10 minutes. The
Polaris correction is more than good enough to get you within 5 minutes
of angle.
