Offline Sight Reduction

1. Trip Info & Assumed Position

Date

Celestial Body

Name

Notes

Lat (Deg / Min / N-S)

Lon (Deg / Min / E-W)

Timezone Offset (UTC Offset in Hours)

e.g., -4 for EDT, -5 for EST, +0 for UTC

2. Observations & Corrections

OBSERVATIONS

Time (24-hour)

Height (Deg / Min)

Clock Error (seconds)

Fast: watch reads ahead of actual time (subtract). Slow: watch reads behind (add).

Average of Observations

Local Time: --:--:--

Local Time corrected: --:--:--

UTC Time: --:--:-- UTC

Hs (Sextant Height): --° --.-'

Sextant Altitude Corrections

IE (Min / On-Off Arc)

Dip (Min, always −)

H (Apparent Altitude): --° --.-'

Alt Corr (Min / +/-)

Add'l Corr (Min / +/-)

Ho (Observed Altitude): --° --.-'

Offline Almanac Cache

Pre-download almanac data (GHA/Dec for the Sun, Moon, planets, and navigational stars) while you have a connection, so auto-fill keeps working offline afterward. Dates below are UTC. Each day makes ~24 requests to USNO's free server, so for a routine top-up, a few days is usually plenty \u2014 14 days is the most allowed at once.

From (UTC)

To (UTC)

No almanac data cached yet.

3. Nautical Almanac Data

Auto-fill with cached data

SUN

0h UTC, Jun 2 Base (Deg / Min)

1h UTC, Jun 2 Next (Deg / Min)

GHA

Declination (Deg / Min / N-S)

Interpolated GHA: --° --.-'

Interpolated Declination: --° --.-'

LHA (Local Hour Angle): --° --.-'

Sight Reduction Results

Hc (Calculated Height)

--

Intercept

--

Zn (Azimuth)

--

Plot

Azimuth to body Line of Position (LOP)

Add to a Fix

Fix

New fix name

Sight Reduction Calculator