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Old 16-10-2011, 03:27   #46
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Re: Celestial Navigation Help Needed

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Originally Posted by roberto11 View Post
i'm now crossing the atlantic on a yacht, the weather condition are exceptional and we are "playing" with the sextant.
we have internet on board but not the ho 249 tables
at the moment i'm using the tables provided in the Admiralty Nautical Almanac but i don't like this tables too much.

thanks for your advices
Roberto

For sun sights, try
Sun Sight

I've found this to be very good. No almanac needed.
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Old 16-10-2011, 07:57   #47
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Re: Celestial Navigation Help Needed

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Originally Posted by roberto11 View Post
hello,
i found this old post and i would like to know if there are some news about 'digital ho 249' tables,
is it possible to find a digital copy of this tables ??
free or to buy !!
i'm now crossing the atlantic on a yacht, the weather condition are exceptional and we are "playing" with the sextant.
we have internet on board but not the ho 249 tables
at the moment i'm using the tables provided in the Admiralty Nautical Almanac but i don't like this tables too much.

thanks for your advices
Roberto
Hi Roberto
You can download my free book "Celestial Navigation in a Teacup" and free software "Teacup Celestial" (for Windows) from my web site: Celestial Navigation
It is completely self-contained with no need for any tables or almanacs. It has a very nice sight planner also, plots your position, and is easy to use.

Rodger
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Old 16-10-2011, 08:28   #48
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Re: Celestial Navigation Help Needed

Thanks Carina PDX,
Was exactly what I was looking for !
Thank you Jamel and Nigel1, Dragonflyer!!
I will check the sites you suggested me but some of the guys work with me want to do their sight for the yacht master exam and they want to learn how the tables works.
We worked with the tables of the Nautical Almanac edited by the Admiralty but is a long work and not so accurate!
Thanks again everybody

Roberto
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Old 16-10-2011, 11:13   #49
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Re: Celestial Navigation Help Needed

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Originally Posted by DragonFlyer View Post
Hi Roberto
You can download my free book "Celestial Navigation in a Teacup" and free software "Teacup Celestial" (for Windows) from my web site: Celestial Navigation
It is completely self-contained with no need for any tables or almanacs. It has a very nice sight planner also, plots your position, and is easy to use.

Rodger
Thanks Rodger, looks like an impressive piece of software, like the planner facility.
Much appreciated
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Old 17-10-2011, 10:52   #50
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Re: Index Error zero

........

I am sure that sights taken on the water will be nowhere near as precise.
.......

Maybe not, but don't forget that celestial navigation was first used as a primary source of positioning. Just go 30 years back, at sea on commercial ships, we were still taking sights, morning and evening, plus the merpass every noon. And we never got lost.

At that times, and today, 1 minute on the sextant was a mile. And we got a cocked hat with a mile size, we were more than happy.

Getting a position during daylite with the sun and Venus was also very satisfying.

Good sailing

JHardy
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Old 17-10-2011, 11:22   #51
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Re: Index Error zero

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........



Getting a position during daylite with the sun and Venus was also very satisfying.

Good sailing

JHardy
Nice to see one else using this method.
I was showing our two deckie apprentices how to do this last year and they were gobsmacked that Venus could be used during the day.
I'm of the opinion that celestial nav is becoming a dying art on commercial ships, I would hazard a guess that even the lecturers at nautical colleges would now struggle to take a sight
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Old 17-10-2011, 12:24   #52
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Re: Celestial Navigation Help Needed

There are a couple of things that celestial navigation can do to regain widespread use.
1. In the old days you didn't have any choice, as a result every effort was made to get as much accuracy as you could with primative unreliable instruments that had their own built in erros, and yes; you can take a sight reading off of every celestial body visible from the naked eye or the small telescope on the sextant, but most sightings are going to be taken off of a couple of easy to find objects, moon, sun, favorite constellation, etc...

In the old days magnetic deviation, variation, were used to plot a DR course across oceans. Now all I need is to get within 1/2 degree, to make the buoy at the channel entrance, do I really need the compass formula to get my absolute true heading,...no, never missed that channel yet. 94-96 degs will get me from my favorite fishing spot to one of the two jetties, 95 and I pass cleanly between them.
My modern compass is more accurate than my eyesight.

The same is true for celestial navigation. DO you really need to add in all of those errors? Or just get accurate sight tables, a good sextant, and a good quartz watch, to get within 50 miles, I rarely try to find an island smaller than that.
My primary navigation will always be the GPS, the sextant is just a backup, and to verify the GPS is working. Yes you need to take all factors into account to get <1 mile accuracy, but my GPS tell me when I cross the street. NO amount of sight tables will ever get that accuracy. If the GPS fails I just need to make landfall, a simplified system will do that. Unfortunately I don't yet have the experience to know what factors I can safely leave out.
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Old 17-10-2011, 12:44   #53
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Re: Celestial Navigation Help Needed

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Loosends,

Out of curiosity, what is your watch "rate of error"? What kind of time piece are you using.

I have a Swiss Army pocket watch that has a rate of error of only (-) 1/15 sec. per day verified by SW radio time signal.

Take care.

Tgoz
I guess times have changed. In the "olden days" (pre satnav, remember satnav?) the ship's chronometer had a book where the error was recorded, usually once a day when receiving a time signal. The chronometer itself was on gimbals in a box and never corrected except if it went ashore for repairs or cleaning. Besides the error, the temperature was recorded. It was a good chronometer if the rate of change was consistent. It was the second mate's job to wind the chronometer every day, seven and a half turns. The theory behind this was to use the same part of the spring all the time. Now a $9.99 Timex is more accurate.
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Old 18-10-2011, 10:42   #54
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Re: Celestial Navigation Help Needed

My watch gains .027 seconds per day, how many miles is that?
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Old 18-10-2011, 14:04   #55
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4 seconds of time is 1 minute of distance (ie. 1 mile). So your error is 0.00675 miles. FA.
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Old 18-10-2011, 16:14   #56
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Re: Celestial Navigation Help Needed

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My watch gains .027 seconds per day, how many miles is that?
How old is the watch?
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Old 18-10-2011, 17:36   #57
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Re: Celestial Navigation Help Needed

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Originally Posted by Vasco View Post
I guess times have changed. In the "olden days" (pre satnav, remember satnav?) the ship's chronometer had a book where the error was recorded, usually once a day when receiving a time signal. The chronometer itself was on gimbals in a box and never corrected except if it went ashore for repairs or cleaning. Besides the error, the temperature was recorded. It was a good chronometer if the rate of change was consistent. It was the second mate's job to wind the chronometer every day, seven and a half turns. The theory behind this was to use the same part of the spring all the time. Now a $9.99 Timex is more accurate.
I forgot to mention, to get a chronometer rating, the loss or gain was 6 seconds or less a day.
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Old 18-10-2011, 18:24   #58
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Re: Celestial Navigation Help Needed

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I forgot to mention, to get a chronometer rating, the loss or gain was 6 seconds or less a day.
And also, woe betide the second mate who forgot to wind the chronometer, I only saw it once, not a pleasant sight, the Old Man on the ship was a pr*%k of the first order, he had the second mate sacked, the fact that the OM was never sober the whole trip was by the by
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Old 18-10-2011, 18:28   #59
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Re: Celestial Navigation Help Needed

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Originally Posted by Vasco View Post
I guess times have changed. In the "olden days" (pre satnav, remember satnav?) the ship's chronometer had a book where the error was recorded, usually once a day when receiving a time signal. The chronometer itself was on gimbals in a box and never corrected except if it went ashore for repairs or cleaning. Besides the error, the temperature was recorded. It was a good chronometer if the rate of change was consistent. It was the second mate's job to wind the chronometer every day, seven and a half turns. The theory behind this was to use the same part of the spring all the time. Now a $9.99 Timex is more accurate.
We are still required to carry a ships chronometer, and record the daily error in the correct log....

Although, the cheaparsed AA battery powered pieces of junk we have these days are never looked at by anyone other than the 2nd Mate who records the error....
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Old 18-10-2011, 19:20   #60
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Re: Celestial Navigation Help Needed

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We are still required to carry a ships chronometer, and record the daily error in the correct log....

Although, the cheaparsed AA battery powered pieces of junk we have these days are never looked at by anyone other than the 2nd Mate who records the error....
Interesting, didn't think they'd keep that going. Does the Second Mate wind all the ship's clocks every Sunday too?
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