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  #1  
Old 02-04-2012
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Celestial Navigation HELP!

Is there anyone here that can help me with some celestial navigation issues? Willing to pay someone money via PayPal for some help...just have a few questions that someone with decent knowledge should be able to answer.

Thanks in advance!

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Old 02-04-2012
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Does this thread help?

Not a war, just a sextant question.
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Old 02-04-2012
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Minn - thank you! Can you check your PM?
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Old 02-04-2012
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You won't be able to PM until you post enough. Why not just ask your question here. Someone may be able to answer it. I'm not stepping up as the CN guru by any means.
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Okay, here is the deal: I am in a contest right now that had numerous steps, and I'm on the last step which deals with celestial navigation. I've done all kinds of reading on it and I still don't think I'm getting what I need to know so I was hoping someone with a little more knowledge may be able to help me out. I also am in somewhat of a race so don't have much time to read a lot of material to learn. Anyways, my questions deal mostly with navigational stars and the first point of aries, and I think are pretty basic. Is that something you could help with if i typed the clues here?
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Here are various clues, in no specific order:

I am standing at the first point of Aries.

The sky is going west to east from my bow.

My Navigational Star is directly ahead and beckons me east.

Navigate by my Navigational Star's value

My Navigational Star appears at the North Pole

My Navigational Star will appear in 2 hours

Degrees and Hours in equal measure

I also think I may have a list of numerous U.S. cities but I'm not sure which ones to use or even if they are necessary.

These clues were not written to be for experts in this area, but for people like me who likely have no knowledge and just need a little bit of help to figure it out.

Last edited by njlw226; 02-05-2012 at 12:13 AM. Reason: More info
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Old 02-05-2012
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Bumping for help...difficult to explain but would be much easier over the phone. Will pay via paypal for help!
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Old 02-05-2012
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1. the celestial bodies rise in the east and set in the west
2. 1st point of Aries is the Venal equinox and the first sign of the zodiac
3. Polaris is the North star.
4. A celestial body appearing to move eastward is caused by planetary precession.
5. 1 hour is equal to 15 degrees of longitude. (the rate of the earth turning)
6. Even though the Moon appears to rise in the east and set in the west, it really revolves eastward around the earth.
7. It is daylight and civil twilight is about 2 hours away, and when civil twilight you can see the horizon. When you can no longer see the horizon it is nautical twilight until the center of the sun is more than 18 degrees below the horizon.
The cities are in various time zones. The meridian of the zone is exactly in the center of the zone. And the zone extends 7.5 degrees to each side in longitude. Of course some zones are twisted due to local or national politics.
8. As far as the sky is going west to east you are watching clouds being pushed eastward due to weather patterns of the area you are in. Or your magnetic compass is really in need of correcting.
9. Star value? Need more data for that one... Too many variables
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Old 02-06-2012
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Quote:
Originally Posted by njlw226 View Post
I am standing at the first point of Aries.
This is a point on the sky; you can't literally standing on it. Either this means
a) "Imagine you are co-moving with the sky and located at the first point of Aries;" or
b) "At a particular moment in time, the first point of Aries is directly overhead."

I think (b) is more plausible.

Quote:
The sky is going west to east from my bow.
Again taken literally this doesn't make a lot of sense. Maybe we shouldn't interpret it as motion; it could be simply that if you look out from the bow and then look up your eyes are scanning the sky from west to east, i.e., the boat is heading west. However....

Quote:
My Navigational Star is directly ahead and beckons me east.
Kind of contradicts my guess from the last clue.

Quote:
Navigate by my Navigational Star's value

My Navigational Star appears at the North Pole
Hm. I'm guessing "appears at the north pole" means "is visible if you're standing at the north pole", which tells you the star is in the northern hemisphere.

Quote:
My Navigational Star will appear in 2 hours
Degrees and Hours in equal measure[/quote]

CN doesn't measure anything in hours. Astronomers measure Right Ascension in hours, though. RA increases east from the first point of Aries, and 24 hours is a full circle through the sky. Sidereal hour angle increases west from the first point of Aries, and 360° is a full circle.

One useful thing about RA is it tells you how long until a given star passes overhead. Maybe this can be used in conjunction with the previous clue about the star appearing in two hours. But "appearing" usually means "rising", which is dependent on lots of things. However, maybe we can make some simplifying assumptions and pretend those other factors aren't important, like:

1) Assume the height of your eye above the surface of the ocean is zero, so the visible horizon is the true horizon.

2) Assume your latitude is the same as the star's declination, so the star will rise due east (or is it due west in this fantasy world?)

In that case, if the star will appear over the horizon in two hours, it will be overhead in eight hours, so its right ascension (since at this moment you're at the first point of Aries) is 8h. 8h is 120°, so the sidereal hour angle of the star must be -120° or 240° (it's minus 120° because RA and SHA increase in opposite directions).

Unfortunately no navigational star as a sidereal hour angle of exactly 240°. The two closest stars are
- Pollux: SHA 243°, declination N 28°
- Avior: SHA 234°, declination S 59°

Of those, obviously only Pollux is visible from the north pole, so I'm guessing that's your navigational star.

Also interesting is that Pollux happens to be visible in the evening at this time of year.

Of course, it's also possible that they're not using one of the standard navigational stars. I'm not really motivated to check other stars.

Anyway, assuming Pollux is the star, your latitude is 28° (we assumed earlier that the star's declination is our latitude). Unfortunately I don't think there's enough information to determine longitude. The clues describe a bunch of observations that would be the same regardless of what longitude you made them from.

However, you said you had a list of U.S. cities. 28°N intersects the U.S. only in southern Texas (just north of Corpus Christi, 97°03'W) and Florida (St. Petersburg/Tampa area in the Gulf side, and Palm Bay on the Atlantic side; 82°48'W and 80°36'W, respectively). So if we're supposed to assume that you are just leaving/arriving at a U.S. city, it could be one of those places, though Palm Bay does not look like a good Atlantic port to be heading due east from.

So if we're heading out from a U.S. port, I'm guessing Corpus Christi, TX, 28°N 97°03'W).

If we're arriving, I'm guessing St. Petersburg, FL, 28°N 82°48'W.

If this was happening yesterday, the time wound be nearly 3pm.
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Old 02-06-2012
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You can't stand on the First Point of Aries. It's imaginary. Even if you could find that massless point, you'd only survive for microseconds in the vacuum of space.
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