Author Topic: Star sight lat and long obs  (Read 4877 times)

Janet Jaguar

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Re: Star sight lat and long obs
« Reply #15 on: December 11, 2014, 07:17:16 am »
anything that comes with storms means you can't see sun or stars.  GPS is a very decent substitute until the sky clears up again.  :)

Kevin

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Re: Star sight lat and long obs
« Reply #16 on: December 11, 2014, 03:47:12 pm »
Good to know that if a solar flare or malign superpower knocks out the GPS satellites navigators remember how to plot a position using old techniques. Mind you, I think getting a star fix in the sort of 40 foot waves we've been having round here in the last few days must have been a bit difficult!

Sometimes impossible indeed. But if you can't look up - look down.

AvastMH

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Re: Star sight lat and long obs
« Reply #17 on: December 11, 2014, 04:37:04 pm »
"But if you can't look up - look down."

Kevin - if you can tell where you are on the ocean deep by looking at the top of your boots I'm more than awestruck.  ;D  ;)

Kevin

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Re: Star sight lat and long obs
« Reply #18 on: December 11, 2014, 09:55:32 pm »
There are many lines of position - some tell you where you are, and some tell you where you AREN'T. For looking down we use the lead line (or echo sounder) - and if you stay off the 10 fathom curve (an LOP) you won't find Black Rock http://www.nauticalcharts.noaa.gov/mcd/learnnc_soundings.html the hard way - it is Foul : )

Janet Jaguar

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Re: Star sight lat and long obs
« Reply #19 on: December 11, 2014, 10:16:07 pm »
That makes it sound simple - it probably isn't anything of the sort in practice but the theory isn't confusing. :)

AvastMH

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Re: Star sight lat and long obs
« Reply #20 on: December 11, 2014, 11:27:18 pm »
There are many lines of position - some tell you where you are, and some tell you where you AREN'T. For looking down we use the lead line (or echo sounder) - and if you stay off the 10 fathom curve (an LOP) you won't find Black Rock http://www.nauticalcharts.noaa.gov/mcd/learnnc_soundings.html the hard way - it is Foul : )

Oh right!  That makes sense. I have a friend who will be very interested to work through this with me at Xmas.  And I found my star charts which will help I guess.  :)

Kevin

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Re: Star sight lat and long obs
« Reply #21 on: December 12, 2014, 02:36:21 am »
There are many lines of position - some tell you where you are, and some tell you where you AREN'T. For looking down we use the lead line (or echo sounder) - and if you stay off the 10 fathom curve (an LOP) you won't find Black Rock http://www.nauticalcharts.noaa.gov/mcd/learnnc_soundings.html the hard way - it is Foul : )

Oh right!  That makes sense. I have a friend who will be very interested to work through this with me at Xmas.  And I found my star charts which will help I guess.  :)

If you are seriously interested maybe we should have a navigation class on the forum? It seems rather daunting looking over the whole subject, but if you break it down into its components it isn't so bad. Each step is basically just looking stuff up in the Nautical Almanac or the Sight Reduction Tables and doing some basic math and plotting.

The easiest thing is to start with is Latitude by Polaris - there are only a few steps and the solution is calculated rather than plotted AND you get a pure latitude LOP. The instructions are in the back of the Nautical Almanac.

AvastMH

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Re: Star sight lat and long obs
« Reply #22 on: December 12, 2014, 10:12:09 am »
I'm certainly interested Kevin, but the likelihood of me ever using it in earnest is vanishingly low and I don't want to cause you a lot of distracting work. What do you think? :)

Kevin

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Re: Star sight lat and long obs
« Reply #23 on: December 13, 2014, 12:17:56 am »
I'm certainly willing to answer questions and provide tips. I can't say everything is on the tips of my fingers any more since I've not sailed in a navigating capacity in many years now. I still have my sextant tho...

AvastMH

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Re: Star sight lat and long obs
« Reply #24 on: December 13, 2014, 02:55:12 pm »
Right you are - I'll let you know how I get on over xmas! :D