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Old 16-09-2016, 20:14   #1
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Cel Nav Question For Expert - Part 2

I asked in prior thread if practicing cel nav in Colorado at 1 mile above sea level would impact sun sight practice with artificial horizon. Answer: no.

So, now that I'm well into sun sight practice I have a two questions and a comment:

First, I'm using a newly purchased Davis plastic sextant and Davis artificial horizon. I can't complain about the sextant, but the Davis artificial horizon leaves a lot to be desired. Is it true I can replace the art. hor. by simply using a plate full of some sort of oil? If not, what is the purpose of the 45 degreed angled glass with the Davis art. hor.? I'm just wondering if the glass has something to do with things....outside being a wind shield...which doesn't work with water. I'm a degreed engineer so I'm trying to rationalize angles.

Second, I'm finding cel nav and awesome learning experience but perplexing. The book I'm using to learn always assumes an approximated Long and Lat. Is that the only way to do it? What if I don't know my Long and Lat? As in I was sucked to sea by a beautiful Mermaid (I'm thinking Jessica Alba) from Colorado to some point in the Pacific. In other words, the gorgeous woman put me somewhere on the earth without reference; AKA an argument with the wife. (Which I'll note, if you apply the same math as required for cel. nav. apparently your wife is a beautiful, but argumentative mermaid. If you are both the same (sex for those of you drinking), you subtract some number from some other number, if you are opposite you add two numbers. Or, if you can't tell, pick one or the other.) Oh geez, I'm so dizzy.

Comment:
I went out to turn the grill on for dinner. Cel nav has me so confused I didn't know to turn the grill knob clock wise or counter clock wise. Apparently, the knob only goes one way..But would go one way clockwise on the northern hemisphere, else it goes counter clockwise.

Last Question:

Is there an app that plots the curves/LOP/GP/Physical Lat-Long on the surface of the earth as an cel. nav. learning tool? I hate to use the word 'app' as I'm a 50 year old mechanical/software engineer. In translation, does a tool software or physical exist? If not, I'm thinking I'll build one and charge a million per use. Small demand, big effort equals million price;-)
Bernie
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Old 16-09-2016, 20:29   #2
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Re: cel nav Question for Expert - Part 2

The glass on the artificial horizon is to protect it from wind.

You need to know roughly where you are to determine where you are using celestial using a forenoon / afternoon sight or stars / planets

The noon sight does not require a DR if you just can catch the sun at its zenith; that will give you a latitude and rough longitude. You can also use Polaris for a latitude.

There are lots of apps available.
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Old 17-09-2016, 05:27   #3
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Re: Cel Nav Question For Expert - Part 2

Its so much easier if you have a half decent assumed position, it doesnt really need to be super accurate, normally within 1 deg (approx 60 miles) or so is Ok.

I guess you could plot a whole series of position lines from a series of AP's if you had no idea of your position and gradually narrow your position down over a series of sights, but in reality it would be easier to take a bearing of the sun, and use that to find a rough starting AP using great circle calcs, or just rough plotting on a world chart? After a few sights you would quickly know where you are. Or you just take a round of stars, and play with AP's until they work out.

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Old 26-09-2016, 15:07   #4
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Re: Cel Nav Question For Expert - Part 2

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Originally Posted by Snowpetrel View Post
Its so much easier if you have a half decent assumed position, it doesnt really need to be super accurate, normally within 1 deg (approx 60 miles) or so is Ok.

I guess you could plot a whole series of position lines from a series of AP's if you had no idea of your position and gradually narrow your position down over a series of sights, but in reality it would be easier to take a bearing of the sun, and use that to find a rough starting AP using great circle calcs, or just rough plotting on a world chart? After a few sights you would quickly know where you are. Or you just take a round of stars, and play with AP's until they work out.

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Captain Sumner's method no less..... which pre-dated the publication of Marc St Hilaire's method by many years...

Worth reading about....
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