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  #1  
Old 01-11-2013
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sextant practice

It's the middle of the winter and looking for a new hobby until it gets warm enough to sail. For lack of a better idea I was thinking about teaching myself celestial navigation. Is this possible in the midwest? Can I use an artificial horizon such as Davis Artificial Horizon, or would I be better of using something such as this; Practice Bubble Horizon

I was also thinking about buying the Davis Mark III plastic sextant. Will this work just fine, I am just planning on using this to learn on. Does anyone have any tips that they would like to share?
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Old 01-12-2013
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sextant practice

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Old 01-12-2013
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Re: sextant practice

I learned using a cheap $35 Davis sextant and an artificial horizon. Try using just a bowl of water as an artificial horizon instead of buying one. It's a neat skill to learn.
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Old 01-12-2013
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Re: sextant practice

I cant comment on the Davis Mark III, but I was self taught on Davis Mark 15 and their Artificial Horizon. Although the Davis Mark 15 (and 25) takes a lot of criticism for its "plastique" composition, it is a good little instrument, and not any less accurate than my Astra IIIB at four times the cost. With the Davis Mark 15 and their artificial horizon, I was able to shoot positions to within a 1/4 to 1/2 mile of GPS - well within a landfall sighting.

As far as teaching publications go, there are a lot out there, most of which will have you cross-eye and tearing your hair out shortly into them. The best I found was Andrew Evens' "Step-by-Step Sextant User's Guide". In it, he demystifies and simplifies the whole process.

Good Luck!
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Re: sextant practice

erps taught me how while floating off his extended backyard: Hope Island. It's interesting, and not too tough to take a noon site.

I then taught my son:


The above picture was taken aboard the Schooner Adventuress, north of Stuart Island...
Sound Experience
A 100 foot schooner is a nice stable platform for practicing.

I was surprised that the Adventuress didn't have one, so we donated it.... Immediately, they started training the other crew members on the sextant, using the deck as a chalkboard..

It was a special moment.

Thanks, Ray!
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Re: sextant practice

Quote:
erps taught me how while floating off his extended backyard: Hope Island. It's interesting, and not too tough to take a noon site.
I had forgotten all about that. Did I have mine on board, or did you have yours. I've since been handed down a Davis Mark 15, I haven't taken it out of the case yet to give it a try. I've been thinking about buying a three armed protractor to plot a position on the chart with relative angles. That makes the sextant a pretty useful tool for coastal fixes, well if the GPS quits working.
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Re: sextant practice

GREETINGS EARTHLINGS:- Get and keep good Time Go SAFE
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Old 01-13-2013
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Re: sextant practice

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Originally Posted by erps View Post
I had forgotten all about that. Did I have mine on board, or did you have yours. I've since been handed down a Davis Mark 15, I haven't taken it out of the case yet to give it a try. I've been thinking about buying a three armed protractor to plot a position on the chart with relative angles. That makes the sextant a pretty useful tool for coastal fixes, well if the GPS quits working.
I had the good one that I inherited. Picked up the plastic one in the giveaway bin at our club... Plastic one was fine to practice with.
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Re: sextant practice

I downloaded "Step-by-Step Sextant User's Guide" and ordered the Mark 3 sextant and the artifical horizon to practice on. Can anyone give me a brief primer on what I am going to have to do to correct for the fact that I am above sea level when taking my sights?
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Old 01-13-2013
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Re: sextant practice

Quote:
I downloaded "Step-by-Step Sextant User's Guide" and ordered the Mark 3 sextant and the artifical horizon to practice on. Can anyone give me a brief primer on what I am going to have to do to correct for the fact that I am above sea level when taking my sights?
My recollection is that the altitude you're concerned with is your altitude above the horizon. On the sea, that's the height of you eye above sea level. If you were in a shore side building, using the sea as your horizon, then your altitude would need to be applied. But it's my recollection that there is no DIP correction (height of eye above water/horizon) when using an artificial horizon, but the angle of the celestial object you're taking your sight on will be half of the angle indicated on the sextant.

They used sextants in airplanes to get around in the old days with artificial horizons and altitude didn't play into it (IIRC)
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