A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Brian Walton
Date: 2020 Oct 18, 07:49 -0700
The River Severn, which with the Bristol Channel forms the border between South Wales, and South West England, has an impressive tide range. I am constrained from entering by Covid19 rules which affect lock-keeper hours, and cause my crew to quarentine the whole family if one member needs surgery. This gives me time to consult my “ cloud” photo library.
This reveals that Neville Maskelyne, Royal Astronomer from 1755 to 1811, used log-versines, called “ log risings”, together with log-sines, and log-secants and log-cosecants. These 2 latter tables are included in the Imram’s copy I have to hand, and return Right Ascension.
I may now proceed to reduce sights as might have my great-grandfather in 1890, using an appopriate combination of the above.