A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Paul Bedel
Date: 2018 Aug 21, 13:45 -0700
A first calculation with observations of Altair and Arcturus give a value of latitude wich is Lat = 8° 28,9' S. Then it's possible to calculate the local hour angle which is 303° 52,1' for Altair and 27° 40,2' for Arcturus; longitude is then Long = 14° 19,5' W.
With those elements, it is possible to calculate the elements of the five Sumner's lines:
Moon: intercept, +0,4', Z= 252,8°. Altair: intercept, 0,0', Z = 074°. Antarès: intercept, +0,7', Z = 163,6°. Arcturus: intercept, 0,0', Z = 315,5°. R. Kent: intercept +1,5', Z = 192,6°.
Without other calculations and just a graphical construction, it seems that the fix, with the 5 Sumner's line is in Lat = 8° 30' S Long = 14° 20' W (rounded to 1').
Ascension islandis not very far.