Celestial navigation tables

WaterThruSun

New member
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NW Montana
I have developed a computer program to calculate the line of position (LOP) as a function of the latitude of the observer, and the altitude and parameters of the star. The output is the Greenwhich hour angle of the observer.

Is anybody interested in this kind of stuff or is this useful? I can very easily produce the tables for the main sailing stars and post them to this forum, if you find them useful.

View attachment 510776
Amazon just delivered a sextant. Now I need a class, book. Attempting to de-tech backup, as in, got a woodstove-oven backup . Your program might help me. Aloha, fave Whiner Drama Queen

 

sledracr

Super Anarchist
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PNW, ex-SoCal
Now I need a class, book. 
When I decided to re-learn the craft after several decades away from it, I used David Burch's book 

Amazon.com: Celestial Navigation: A Complete Home Study Course, Second Edition eBook : Burch, David, Burch, Tobias: Kindle Store

Available as printed book or e-book on Kindle.  He also teaches classes (mostly online these days, I think)

I found the book to be clear on the concepts, presented the topics in a logical step-wise sequence, and the exercises are excellent.

Plus he's pretty accessible through the starpath forums...

$.02

 

Svanen

Super Anarchist
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Whitby
I wonder how lone sailors (like athletes) found their position before the GPS. Sure they couldn't do DR 24h. So maybe they used some initial trigonometry to get the DR coordinates for the charts?
You can easily DR for 24 hours. Hell, you can cross an entire ocean entirely by DR; and in pre-GPS days, more than a few ‘navigators’ did just that.

In any case, using the intercept method an assumed position doesn’t have to be particularly accurate. Deduced reckoning is used for advancing an LOP between sun shots, but you only need three or so hours between those two sights.

I cannot recommend Mary Blewitt's book highly enough.
That book is quite concise, and many people swear by it. I have a copy of the 12th edition, but have never been much impressed by it. For my money, the standard RYA text (G78) is better.

g78-rya-astro-navigation-handbook_0_1616108492_700x700.png


But certainly there are many textbooks available, and they are pretty much all decent. The important thing is to practice ... just reading a book - any book - is insufficient.

 
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ardsur

New member
4
1
thailand
hi skippers if you are interested in using the Celestial Navigation (again?), from the easy position of a comfortable chair, there is a virtual sailing website that organise regular sailing races where you can only navigate using the internal Stellarium website, Https://game.realsial.net. They have a tutorial on Celestial Navigation and a manual that explains 3 different methods for how to navigate on the stars. Myself use this game and navigate with 3 stars on Stellarium seen from the e-boat position. for plotting LOP's I do use a website Astron that calculates and draws the lines for you; https://friendsofthevigilance.org.uk/Astron/Astron.html
try it out you will like it, at this moment Realsail is shadow racing the GGR2022
 

slug zitski

Super Anarchist
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You can easily DR for 24 hours. Hell, you can cross an entire ocean entirely by DR; and in pre-GPS days, more than a few ‘navigators’ did just that.

In any case, using the intercept method an assumed position doesn’t have to be particularly accurate. Deduced reckoning is used for advancing an LOP between sun shots, but you only need three or so hours between those two sights.


That book is quite concise, and many people swear by it. I have a copy of the 12th edition, but have never been much impressed by it. For my money, the standard RYA text (G78) is better.

g78-rya-astro-navigation-handbook_0_1616108492_700x700.png


But certainly there are many textbooks available, and they are pretty much all decent. The important thing is to practice ... just reading a book - any book - is insufficient.
Yah

you need a textbook on the boat …sophisticated sight methods that you don’t often use are hard to remember and need a refresher
some young Yachtmaster is always on board practicing for certification and they need a textbook

the best book I’ve ever seen , and the one that I have carried my entire sailing career is …

Self-Contained Celestial Navigation with H.O. 208.​


these are concise tables and the techniques described are aimed at small craft

the longitude at noon sight , once learned, is you most valued daily sight

The technique for constructing you own plotting sheets in a standard lined notebook is very valuable

9627AE8A-6AA2-47AF-9BDB-579B54A5FDA6.png
 

sledracr

Super Anarchist
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PNW, ex-SoCal
the best book I’ve ever seen , and the one that I have carried my entire sailing career is …

Self-Contained Celestial Navigation with H.O. 208.​


+1
It's a great all-in-one volume, with a somewhat simpler process and tables. Well worth the effort to find a copy.

Is the HO-208 approach as "accurate" as the approach using the full tables (HO-229 and HO-249, plus Nautical Almanac)? Maybe, maybe not... but it works. And it's just one book to carry around.
 

slug zitski

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The complete tables simply take up to much space ..add in sextant almanac, text , tools, plotting sheets…and that stuff overwhelms a small boat

this is why people are tempted to go digital

i think digital is a huge compromise
 

sledracr

Super Anarchist
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PNW, ex-SoCal
The complete tables simply take up to much space ..add in sextant almanac, text , tools, plotting sheets…and that stuff overwhelms a small boat

this is why people are tempted to go digital

i think digital is a huge compromise

Agreed. My evolution, back in the day, was...

-- bring a metric ton of stuff (sextant, plus timepiece, plus HO-249, HO-229, Nautical Almanac, worksheets, plotting sheets, plotting tools, etc, etc, etc)

-- bring HO-208, (plus sextant, plus timepiece, plus worksheets, plus plotting sheets, plus plotting tools, etc, etc)

-- bring HP-41 with the "nav pack", (plus sextant, plus timepiece, plus plotting sheets, plus tools, etc, etc)

The reality is that the process itself is fairly easy... The evolution over time was more about having "less stuff" to carry around.

Current phase in my evolution? I can (and do) carry searchable PDF copies of all the necessary resources on my laptop, or my phone, or my Kindle. So the additional "burden" of doing the full-table approach is zero.

At the end of the process - no matter which approach - it still starts with good sights, and ends with good worksheets and good plotting. In between it's just access to the right set of tables, and some pretty basic math.
 

slug zitski

Super Anarchist
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Agreed. My evolution, back in the day, was...

-- bring a metric ton of stuff (sextant, plus timepiece, plus HO-249, HO-229, Nautical Almanac, worksheets, plotting sheets, plotting tools, etc, etc, etc)

-- bring HO-208, (plus sextant, plus timepiece, plus worksheets, plus plotting sheets, plus plotting tools, etc, etc)

-- bring HP-41 with the "nav pack", (plus sextant, plus timepiece, plus plotting sheets, plus tools, etc, etc)

The reality is that the process itself is fairly easy... The evolution over time was more about having "less stuff" to carry around.

Current phase in my evolution? I can (and do) carry searchable PDF copies of all the necessary resources on my laptop, or my phone, or my Kindle. So the additional "burden" of doing the full-table approach is zero.

At the end of the process - no matter which approach - it still starts with good sights, and ends with good worksheets and good plotting. In between it's just access to the right set of tables, and some pretty basic math.
To be honest I don’t use a sextant anymore

it comes out when crew…Yachtmaster types who need to record a passage for licensing…are on board
paper all over the saloon table for weeks…
tables, plotting , handwork are easiest to pass on and require no laptops or calculators , or degree minute, seconds decimals

Many hand work techniques like distance off an island or whatever by horizontal sextant angle are valuable seamanship

I’ve got a pretty good iPad celestial App…easy to use and not expensivec
 

sledracr

Super Anarchist
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PNW, ex-SoCal
To be honest I don’t use a sextant anymore

I still have mine on the boat, and still enjoy the "craft" of taking and reducing a sight from time to time (*). But frankly it's just "something I enjoy doing", at this point, not something I depend on.

(*) I took a couple of sights last summer while vacationing at Rosario Marina in the San Juan Islands. An hour or so later I was able to confirm that, yes, Rosario Marina is exactly where it appears on the charts. I can also confirm that quality sights are much easier to take when standing on a beach facing several miles of smooth water <lol>
 

slug zitski

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I still have mine on the boat, and still enjoy the "craft" of taking and reducing a sight from time to time (*). But frankly it's just "something I enjoy doing", at this point, not something I depend on.

(*) I took a couple of sights last summer while vacationing at Rosario Marina in the San Juan Islands. An hour or so later I was able to confirm that, yes, Rosario Marina is exactly where it appears on the charts. I can also confirm that quality sights are much easier to take when standing on a beach facing several miles of smooth water <lol>
In school we were taught how to use an artificial horizon

the class was field astronomy , cartography and we never had access to sea level and a horizon

good technique to practice and perfect
 

Hale Moana

Member
58
54
Morro Bay
Decades ago one of my best friends Jim Hollywood who ran the Windward loft in Dana Point taught celestial nav at OCC. He was a true pro at. I took his class one semester and still have the book that he wrote for the class. I never got good at taking sights. Not enough practice.

While cruising in Mexico with too much time on my hands I started researching how they did cel nav in the early days of sailing. How they did it in the 1600, 1700 & 1800's. From this research I learned that you didn't need to buy a new Nautical Almanac each year. If you had one for a leap year there were simple formulas to correct the info to the current date. I also learned a bunch about how to determine your position at different times of the day. From this I came up with some simple work sheets to do the calculations. Most of these required an accurate watch set to GMT. It was great fun doing this. I still have my sextant on board and an old Nautical Almanac. Drag it out occasionally to dust it off and clean it. Would I toss my GPS's overboard. No way.
 
Still enjoy using this frequently aboard our boat. Will be taking it to Antigua in a few days for the sail north. Can't imagine sailing offshore without it.

First few sights every year are always humbling :)

Spent last night dialing out all the perpendicularity, side and index error. With care a quality sextant should last a lifetime.

This one dates from the day I graduated high school. A fine gift from my father.

IMG_1164.jpg
 
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Good tool

lightweight…easy to wash off , excellent sun sights

stars are seldom used on small craft

View attachment 558779
I had one of these, wish I still had it for the ditch bag.

I will argue about stars and small boats though. I do a lot of stars, usually with a plan for at least 6 before I step on deck with a little diagram of their spread on my notebook, taking the fastest and easiest 3-4.

When I get to Antigua next week I will likely make a routine of it for the overnight passages in prep for Transpac this year.
 
Yah

you need a textbook on the boat …sophisticated sight methods that you don’t often use are hard to remember and need a refresher
some young Yachtmaster is always on board practicing for certification and they need a textbook

the best book I’ve ever seen , and the one that I have carried my entire sailing career is …

Self-Contained Celestial Navigation with H.O. 208.​


these are concise tables and the techniques described are aimed at small craft

the longitude at noon sight , once learned, is you most valued daily sight

The technique for constructing you own plotting sheets in a standard lined notebook is very valuable
My personal favourite text is David Burch's book.
 

Hitchhiker

Hoopy Frood
4,675
1,318
Saquo-Pilia Hensha
Reading this thread prompted me to go find my trusty Davis Master. Lightweight and accurate. Last time I used it though was ‘05 Transpac! My favourite tool is my Celesticomp V. Not just for sight reductions but also calculating distance run and cmg between log entries. Also good for leg planning, although Exp has rendered that a bit redundant! Think I need to freshen my sight taking skills and brush up my maths! Not that I’m going to use it in a race. All the boats I sail on are either too wet or don’t have anywhere to plot!

ADDF71FB-2ABC-4D52-8AC4-19A6FC8EC77C.jpeg
 

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