A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Tony Oz
Date: 2019 May 1, 13:17 -0700
The second week in a raw it is THE excellent weather here for sextant practicing. I'm on a sick-leave so I spend all my free time on the shore.
After a very long sequence of sights I notice that I consistently get an "away" intercepts - 0,75nm on the average.
The IE value is measured to be 0°0,1 (positive value, i.e. to be added), the Sun's SD is either the tabulated (0°15,9') or measured (0°15'48''). The HoE is also known with good precision and accounted for. The clock is just 1 (one) second fast. I either wait for the Sun to touch the horizon or turn the drum only in the incremental direction (to avoid "play" or back-slash).
The only way for me to get near-zero itercept is to let the setting Sun's LL to dip into the sea so that a tiny but noticeable segment of overlap is there...
What am I doing wrong? Is it an abmormal refraction (air temperature is +10°C, atmospheric pressure is 750mmHg)? I see the distant fort being too low on the horizon (~2 arc minutes instead of the usual ~4). The HS is in the range of ~40°~25°.
Only very rarely - if I mis-read the watch - I get "toward" intercept.