Underway - Pacific Crossing Notes: A Sailor's Guide to the Coconut Milk Run - page 120

Setting the Focus
What takes practice to perfect on a rolling boat is actual altitude measurements with a sex-
tant. The more of these measurements we can take and evaluate, the better. We therefore
want to minimize the time spent on sight reduction (Figure 1, step 3) and instead focus on
taking and evaluating sights (steps 2 and 5).
Figure 1: Celestial navigation cycle
In the early days of GPS, continuing the practice of celestial sights was motivated chiefly
by the need for an emergency backup navigation method. Consequently, the focus was on a
minimalistic procedure, using only pencil and paper for the sight reduction step. As a res-
ult, the recreational navigator spent most of his time on tedious computations, consulting
logarithmic tables and filling in forms in a process that - without daily practice - can be as
error-prone and frustrating as filling in your 1040 tax return.
Today, however, it's much more likely that grab bags contain a functioning handheld GPS
rather than a sextant, nautical almanac, sight reduction tables, and a timepiece with known
offset and rate of deviation from UTC. We no longer need to restrict ourselves to a tedious
barebones procedure for safety reasons. Instead, we're free to use one of the countless elec-
tronic calculators that reduces sight reduction to a few keystrokes and to focus our attention
on taking and evaluating sights instead (see Celestial Navigation: Useful Tools below).
Many of these tools also feature an electronic ephemeris which can replace the Nautical Al-