Sunrise Longitude Fix

Sight the sun at Hs ≈ 0° as its center bisects the horizon — FairWinds turns that timing into a longitude fix.

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When

About ±10 minutes around sunrise on the Daily Schedule (sights within about ±20 minutes still classify as sunrise).

Check Solar Times → Sunrise for the predicted UTC (based on your position reference / AP). Timing is tight — a few seconds matter.

In FairWinds (Guided)

1. Open the Sky Tool → Workbook → note Sunrise under Solar Times
2. Near sunrise, tap Sextant and shoot the Sun with the disc half-risen (center on the horizon, Hs ≈ 0°)
3. Open the Sun tab — your sight should show a RISE badge
4. Select that sight so the Sun Worksheet switches to Sunrise / Sunset Fix
5. Review the longitude calculation (observed UTC vs almanac time at 0° longitude)
6. Tap Save to Log

The fix is saved as a Lon fix and appears in Positions.

Why it matters

This is a quick longitude check, not a full lat/lon fix. Use it to gut-check whether your DR longitude is still sane before the morning sun work.

Expert mode

The auto longitude worksheet is hidden. Treat Hs as Ho for this horizon sight (index/dip corrections are not applied yet), compare your observed UTC to Greenwich sunrise from the almanac (1 min ≈ 0.25°), then Fixes tab → Enter Fix → Longitude Fix.

Optional — pairs well with a later noon or star fix.