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Old 25-08-2015, 09:39   #16
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Re: How to do celestial today

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Originally Posted by farshore View Post
The DOD can and has selectively shut off GPS in trouble areas.beautiful!
Very true......... and if things get real nasty, the first things to go will be GPS SATS as a prelude to any hostilities. And, as the government notes, Solar Flares can blind your GPS equipment.

From gps.gov

"Like all radio-based services, GPS is subject to interference from both natural and human-made sources. A GPS unit can lose reception in the presence of devices designed for intentional radio jamming. Solar flares can also disrupt GPS equipment. For this reason, the U.S. government strongly encourages all GPS users to maintain backup/alternative positioning, navigation, and timing capabilities. In addition, the government is currently fielding new GPS signals that are more resistant to interference.

More from gps.gov
Is it true the Air Force doesn't want to use GPS in the future because of its vulnerabilities?

The Air Force is fully committed to continuing its operation and use of GPS in the future. The ongoing GPS modernization program will enhance the jam resistance of the military GPS service, making it more robust. At the same time, the Department of Defense is making prudent investments in alternative positioning, navigation, and timing (PNT) technologies to supplement GPS in times when satellite services are unavailable. This will ensure that future troops have continuous, uninterrupted access to PNT under the most challenging conditions."


The above reference to "alternative positioning" when services are unavailable can be translated to; when the Chinese, Iranians, or Russians shoot our GPS SATS out of the sky.


While GPS is terrific, exclusively relying on it has made us vulnerable.
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Old 25-08-2015, 10:04   #17
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Re: How to do celestial today

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Originally Posted by hodgmo View Post
I created a brief primer detailing the steps in a sun sight reduction (using the NA) to help a friend who also wanted to get back into celestial. It's ~8 MB pdf - PM me if you'd like me to email it to you (I don't see how to post a pdf in the forum).
I'd like a copy, if it's not too much bother. Thanks,
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Old 25-08-2015, 10:16   #18
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Re: How to do celestial today

I dragged around a plastic Davis for a long time before Cecil Lange showed me how to hold it and then a cute Spanish women named Isabela taught me the rest. It isn't too difficult to learn, so it must be easier to remember.
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Old 25-08-2015, 10:35   #19
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Re: How to do celestial today

I download and print relevant almanac pages.

I take a morning sight and then a noon sight. If I miss the morning one, I take the afternoon one. And that's that. I check my astro musings against our gps position when done.

Now for a time I have been considering calculating our longs from Sun/Moon-rises and sets. It seems viable but I have not tried it yet. I would not have to pull out the sextant then, just the note the times.

b.
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Old 25-08-2015, 10:52   #20
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Re: How to do celestial today

Well, I still have an NC 2 an NC-77 and an NC -88 ( the 88 I have probably used for a few thousand sights). But now the almanac is on my tablet, but I print out the pages for the time I will be at sea plus a few and take them with me. 229 and 249 are now in pdf form and easy to keep on my phone and tablet, but there is usually a copy on the ship.

For years, (ever since the advent of GPS) I use the gps as my AP and if my intersect is less than 2 miles I figure all is well.
I find a few crew often want to learn and we work each sight out longhand which keeps my hand in for plotting, but using an app and GPS I can work a sight in a minute or so and it is easy to do.

As an aside, no matter what system you use, I always take three sights of the body, then average the time and the sight, it reduces any error to practically zero, and for new navigators gives them three times the practice bringing the body down, reading the sextant, and taking accurate time.

Michael
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Old 25-08-2015, 12:12   #21
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Re: How to do celestial today

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Originally Posted by fatherchronica View Post
I dragged around a plastic Davis for a long time before Cecil Lange showed me how to hold it and then a cute Spanish women named Isabela taught me the rest. It isn't too difficult to learn, so it must be easier to remember.
Somebody has to say it: "Nothing like 'a cute Spanish women named Isabela' to bring you up to snuff on celestial bodies!" :-0)!

TrentePieds
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Old 25-08-2015, 12:42   #22
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Re: How to do celestial today

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I think there are always two parts to celestial: finding the GP of the heavenly body (isn't it odd how we still use this term, and I am an atheist...) and solving the navigational triangle. Those two functions are why you need two books or tables.

I'd really like a relatively simple iPhone app that would allow this. But those that I have looked for are really expensive and probably do too much.

But it would also be nice to have the app select the best stars for morning and evening sights. And perhaps substitute planets for stars if one happened to provide a good three "star" fix. And possibly compute my position based on two LOPs.

I guess that's why the iPhone app costs $80 or so!

Incidentally, I totally agree about Blackcrow. If you can't say something nice, go to some hate-filled forum and discuss your opinions there, please.

Chuck
I have one... its called Vol 1 of the Air Navigation tables...
The best stars at any given time are highlighted and , by inspection of all offered, you can pick the set that suits you best.

A little wrinkle.... at evening stars start with a bright star in the east...morning stars start with a star in the west.

RE the accuracy of the Air Navigation tables when used afloat... on big ships thats all I ever saw used.... that and longhand.... never saw the blue 6 vol tables being used. I think the accuracy is good enough.
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Old 25-08-2015, 16:45   #23
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Re: How to do celestial today

My dad used to be navigator on yacht trips up to the pacific islands in the 70's - it was pretty important to hit those little islands dead on and he always got it right. I learned celestial and still try to keep a bit of practice in but i havent been too enthusiastic since i realised the best timepiece on the boat was the GPS. I recently bought (as a backup) a geocaching GPS brand new for $20 (last time i looked an almanac cost 3 times as much) - it gives accurate lat-long readings as well as all the other useful GPS stuff. If the GPS sytem clunks I'll quite cheerfully go back to celestial but at the moment it doesnt make sense.
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Old 25-08-2015, 16:56   #24
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Re: How to do celestial today

Teacup Celestial online would be a good place to start. he has free materials and free celestial forms and computer celestial navigation programs. or is it Celestial Teacup? Whatever.
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Old 25-08-2015, 17:29   #25
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Re: How to do celestial today

teacupnavigation.com ---Tom Cunliffes book and site are great and he has short videos. Youtube has videos. Google Celestial Navigation PDF and maybe try the same with the other things.
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Old 25-08-2015, 19:34   #26
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Re: How to do celestial today

[QUOTE=sailsw00;1898766]Oh wise ones:
I used to be pretty good at celestial, having used it and taught it in various locations around the world, but I haven't picked up a sextant since GPS became so available, or since my Tamaya NC-77 became extinct. I want to get current again, but how? Is the Nautical Almanac still published in book form, or just as a download? Is there a generally-accepted program, calulator, or software that most folks use? Any suggestions on this "reinventing-the-wheel" application of technology would be apperciated.
Thanks.


All celestial bases covered here including:
An online Nautical Almanac, sight reduction programs and a plugin to OpenCPN
"The Online Nautical Almanac"
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Old 25-08-2015, 23:42   #27
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Re: How to do celestial today

For about $23 you can get Geoff Kolbe's long term almanac for sun and stars good thru 2050. There are few extra steps but nothing onerous. Book also includes the Nautical Almanac Concise Sight Reduction Tables, aka "Davies". In an absolute emergency I would use them but they are kind of a PITA. I prefer HO-211/Ageton. It's 36 pages long, all addition and subtraction, no multiplication or division plus it uses the DR rather than an AP to plot from. I got mine used for about $5 or you can copy it from the 1984 vol.2 of Bowditch.

For $10 you can get "The S tables"/Pepperday which are a 9 page modification of Ageton.

I'm on vacation and while we were camping on the coast I was practicing with a plastic sextant and reducing using Kolbe and Ageton and getting 2.0-3.5 nm accuracy compared to my known position.

Inland now I tried shooting in a pan of water but don't have the right tables to reduce that.

If you want a site where folks eat and breathe celestial then go here: http://www.fer3.com/arc/
Very sharp bunch of folks, they are still developing and researching celestial, not just rehashing how it was done. They would be happy to help you with any further questions you have.


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Old 26-08-2015, 03:50   #28
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Re: How to do celestial today

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Originally Posted by barnakiel View Post
I download and print relevant almanac pages.

I take a morning sight and then a noon sight. If I miss the morning one, I take the afternoon one. And that's that. I check my astro musings against our gps position when done.

Now for a time I have been considering calculating our longs from Sun/Moon-rises and sets. It seems viable but I have not tried it yet. I would not have to pull out the sextant then, just the note the times.

b.
Longitude from sunrise/set is easy , but it helps to use the sextant, just set it at zero and note the time when it hits.

Another fun one is simultaneous sun and moon for an instant fix.
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Old 26-08-2015, 08:17   #29
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Re: How to do celestial today

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Originally Posted by sailsw00 View Post
Oh wise ones:
I used to be pretty good at celestial, having used it and taught it in various locations around the world, but I haven't picked up a sextant since GPS became so available, or since my Tamaya NC-77 became extinct. I want to get current again, but how? Is the Nautical Almanac still published in book form, or just as a download? Is there a generally-accepted program, calulator, or software that most folks use? Any suggestions on this "reinventing-the-wheel" application of technology would be apperciated.
Thanks.
-Steve, currently sailing out of Porto Belo, Santa Catarina, Brazil
Hi Steve
Yes they print Almanac. Keep the print version the sextant and the watch with the compass. If it is to use a computer to download the Almanac, or you use a software for calculations, it means that you do not need celestial at all. You have two or three gps with map on your smart phone and a hand held and u r ok.

Celestial u will use only in total electrical failure like on Sophia Jean a 55 IRWIN five days out of Newport towards Gibraltar, and was no solar or batteries for handheld. Quite a remote occasion though.

Nowadays with a solar and a handheld plus your smart phone u don't really need celestial.

On the printed book you will see all calculations needed. Better learn the hard way But the challenge with celestial is to take the sight. Exercise with your sextant and if u manage to get an acceptable sight go ahead
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Old 26-08-2015, 08:32   #30
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Re: How to do celestial today

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Hi Steve
.........it means that you do not need celestial at all. You have two or three gps with map on your smart phone and a hand held and u r ok.

Celestial u will use only in total electrical failure like on Sophia Jean a 55 IRWIN five days out of Newport towards Gibraltar, and was no solar or batteries for handheld. Quite a remote occasion though.

Nowadays with a solar and a handheld plus your smart phone u don't really need celestial.
Sputter, sputter, cough, cough...:ban ghead:

That wasn't his question.

He is doing this by CHOICE.
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