Nautical Almanac - Sight Reduction Tutorial / Explanation - for the layperson

This is the only video I wrote a script for. I ended up having to cut out a lot of material so the result is weird inflections in my voice.
Here is a new resource: celestialnavigation.info/


The contents of this video are a result of my enjoyment of this hobby and are for informational purposes only. Learning and gaining new knowledge about CelNav is a lifelong quest. There are about 30 methods of doing celestial navigation, here is one.

One of the most frustrating aspects is having all the accouterments but not knowing what to do once you've taken your sight. Information about doing a sight reduction is limited or obfuscated.
Here I attempt to explain it.

If you have a copy of the nautical almanac and the form contained within, you should be able to follow what I'm doing. Sightings of the stars and planets are very similar to this one but have other adjustments and corrections that a sun sight does not.

You can skip ahead to about 1:12 in the video to get to the meat of it and avoid my disclaimers.

There is one point I want to make clear, I misspoke in the video concerning rounding up the values of A, F and P. Round up only those degrees to the next degree IF THE MINUTES ARE 29 OR LARGER.
Example A= 23° 44' and F= 19° 28' you would round up A to 24 but F would remain 19° when using them to look up figures in the Sight Reduction Tables.

Some other points that may not be clear:

Become familiar with the rules in the corners of the sight reduction pages as local conditions may change their application. B and Declination are generally added if you are in the same latitude as the celestial body, subtracted otherwise.

Final GHA -W longitude or +E longitude = LHA.
If the final GHA number is too small or large to do the sum add or subtract 360 degrees to GHA to get a usable number.
Another point, LHA has to be a whole degree, GHA is based on the exact time of your sextant shot and can't be changed so change your assumed longitude to allow the math to work so the sum (LHA) is a whole degree. Assumed Longitude is an arbitrary number anyhow.
EG:....Final GHA 300° 45'
Assumed Long + 59° E
Result................ =359° 45' LHA ...incorrect
You can't use an LHA of 359° 45' instead change your assumed longitude to 59° 15' and your LHA becomes 360°

Corrections are always welcome.


The easiest to understand book I've found, written in plain language: Celestial navigation for the clueless . It's not a perfect book and has some mistakes but it'll get you there. Search for it on Amazon.

link to another good source of information: thenauticalalmanac.com/Forum/index.php

Still not getting it. Relax, I had the same problem. The solution for me was to do the problems over and over until I had the procedure down. As I made mistakes, I learned from them, later I would realize I had made a mistake and where I had done it before completing the reduction.
This isn't hard to do, learning it is hard. Are you willing to accept the challenge?