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Alex

While you are thinking along these lines, I found a response to the
beginners meridian passage question to be extremely interesting:

Bill

Michael Dorl wrote:

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.

see

http://brunelleschi.imss.fi.it/genscheda.asp?appl=SIM&xsl=multimed&lingua=EN
G&chiave=500044



If you want the book see
http://www.celestaire.com/catalog/products/5722.html or many other sources.
Search for Latitude Hooks and Azimuth Rings Dennis Fischer for other
sources.

I'd think a Nocturnal or a sketch of the position of Ursa Major and Ursa
Minor at Polaris meridian crossing would be a useful life boat adjunct.


Gennaro Sammarco added:

here is a link to whom might be interested in building his own 'nocturnal'.
http://www.mts.net/~sabanski/sundial/tsp/nocturnal.html
enjoy it
Gennaro Sammarco

   

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