AM Sun Sight

Morning sun sight on the Sun tab — the first half of FairWinds’ sun-run-sun (Sun-Run Fix).

← Back to Daily Fixes

When

After sunrise until the noon window on the Daily Schedule (required step).

Aim for sun altitude about 20°–60° — high enough to limit refraction trouble, low enough that the horizon stays sharp. Roughly mid-morning is usually right.

In FairWinds (Guided)

  1. Open the Sky Tool → Workbook → Sun tab
  2. Tap Sextant, acquire the sun, choose Center (default) or Lower limb, align to the horizon, Mark! → Save. Lower limb records a limb Hs; Guided applies +SD so Ho is still the sun’s center.
  3. Confirm the sight appears under Sun Sights with an AM badge
  4. You do not need to compute a standalone fix from this sight alone

Keep this sight. Later, after your PM Sun Sight, you’ll select both AM and PM sights and run Compute Running Fix (see PM Sun Sight / Running Fix).

The Daily Schedule marks AM Sun Sight done when you’ve taken a qualifying morning sun sight.

Check the position reference first

The sight is stamped with the position shown under Reference from at the top of the drawer, and the afternoon running fix measures your run as the difference between this stamp and the PM one. In Guided the default GPS — current position moves with the boat and nothing more is needed. If the dropdown shows Auto — Latest fix or a specific fix, that position will not move between now and the PM sight, the run will come out as zero and the running fix will be wrong by roughly the day's run. Lay a DR mark (course and speed) from that fix first so the reference reads Auto — DR projected. Details: Position reference, DR and the run.

Picking the time

The running fix needs the sun's azimuth to change between the two sights; FairWinds refuses pairs that cross under 5° and anything under 15–20° is poor. When the sun passes high (noon altitude above about 60°, i.e. the sun's declination is within 30° of your latitude), most of that azimuth swing happens in the hour either side of noon, and a 09:00 sight paired with a 15:00 sight may cross at only 10–15°. In that case plan on pairing this sight with one taken within an hour of Mer. Pass., or take a mid-morning sight and a second one near noon. When the sun stays low, well-separated morning and afternoon sights cross comfortably.

Why it matters

In FairWinds the classic daytime position is a sun-run-sun fix: advance the morning LOP by your boat’s run, then cross it with the afternoon LOP. The AM sight is the first of those two lines — not a morning cross with noon latitude.

Expert mode

Capture the same sight (Hs is recorded; Ho stays unset until you correct it). In Expert the reference is never GPS, so the stamped DR is whatever AP Selection resolves to — lay a DR mark from your latest fix before this sight or the stamp will sit still all day (see above). Follow Expert setup: on Correct Hs, apply IC, the prefilled refraction, +SD for a lower-limb sun (prefilled), and parallax (+0.1′); leave dip at 0. See Altitude corrections and refraction. Enter the finished position later via Enter Fix → Running Fix after the PM sight.

Required — first sight for the Sun-Run Fix.