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Thread: Sextants

  1. #36
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    Aug 2010
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    Southern NH
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    1,338

    Default Re: Sextants

    My one experience in celestial was with a Tamaya, and I wouldn't hesitate to go that way again.

    Sight reduction tables and The American Practical Navigator are available from Uncle Sam as free downloads.

    https://msi.nga.mil/NGAPortal/MSI.po...2&pubCode=0013

    https://msi.nga.mil/NGAPortal/MSI.po...2&pubCode=0002

    Allan
    And the Binnacle-bats wore water-proof hats
    As they danced in the sounding sea.

  2. #37
    Join Date
    Aug 2009
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    Olympia, WA, USA
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    1,315

    Default Re: Sextants

    I used a lunar twice. ... Having done it I have no desire to repeat.
    Hm. From what I'm hearing, lunars are definitely in the category of backyard entertainment and skills-building rather than practical navigation.

    My one experience in celestial was with a Tamaya, and I wouldn't hesitate to go that way again.
    I'm seeing some nice Tamayas out there, even if most of them seem to be in India right now.

    Sight reduction tables and The American Practical Navigator are available from Uncle Sam as free downloads.
    Cool! Free downloads are always welcome. Thank you.

    Alex

  3. #38
    Join Date
    Aug 2010
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    BC Coast
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    3,434

    Default Re: Sextants

    Quote Originally Posted by Pitsligo View Post
    Hm. From what I'm hearing, lunars are definitely in the category of backyard entertainment and skills-building rather than practical navigation.

    Alex
    Lunars are not skills building....unless you think learning math begins with Integral calculus or other supposedly higher math....Lunars tables were discontinued because they were a lot more work and there were a number of simpler methods and short tables being developed. Doing lunars now using the tables we have now is much more work than what Slocum was used to. Using our Nautical Almanac it is somewhat more involved.....Certain math guys have worked up methods and computer/calculator programs to make it functionally somewhat easier.....
    Unless you understand the nautical astronomy and the math...please do not boast about doing lunars. Anyone can fill numbers into a calculating spreadsheet and get the answer....It does not make you a Slocum or Cook. Its almost like sailing around the world using GPS and imagining yourself as Captain Cook reborn.
    I have also used HO 229 and HO 249 tables {and a number of other short methods...(I started with raw math, and moved to haversines as a hand working method)}. Either is good, I have the 229 tables but really prefer the HO 249, mainly because of the star table which I used for predicting the best stars....brightest and best crossing angle. This is really helpful when the sky is partly cloudy and you can preset the altitude on the sextant and scan in the approximate direction of the desired star. Once you find it you quickly bring it down to the horizon, mark the time. I generally took two stars, twice each, plus a check star. The two stars would be reasonably close to 90 degrees from each other. I need to calculate only twice and then adjust for the time difference only. The check star was only to confirm.....so five sights (within about 5 minutes in northern temperate regions) and three+ calculations. For stars ..of course you have to work during twilight, when you still have horizons and the brighter stars are becoming visible...in the tropics, that is about 5 minutes...you have to be pretty efficient.

    For what it is worth I never cared for a noon sight as such. I could do an 'intercept' any time but a NOONER, I had to be there when the sun was in position....had to wait for it.....never as really sure as it seemed I'd like to be that I got it right.

    I did not like the moon because it moved too fast. The planets tended to move pretty fast as well.
    Last edited by gilberj; 09-13-2017 at 02:45 AM.

  4. #39
    Join Date
    May 2017
    Location
    Tasmania, Australia
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    92

    Default

    I have a nice Frieburger. A lovely thing to use and look at. It is a big step up from my grandfathers Davis mk15. We used Kelvin Hughes sextants when I was at sea. Very nice, I'd love to own one.

    Sent from my SM-G930F using Tapatalk

  5. #40
    Join Date
    Mar 2011
    Location
    Gold Coast Australia
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    2,003

    Default Re: Sextants

    I must admit to have always used a noon shot and probably also enjoyed the associated structure that it gave our day.
    After a year of navigating we started using star sights and never looked back.

    Unlike the The stressed out cruisers overheard on the VHF approaching the Tuamotus , who having just had a series of low Sat Nav passes where not really sure of their exact positions.

  6. #41
    Join Date
    Mar 2008
    Location
    Long Beach, CA
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    2,883

    Default Re: Sextants

    The nice thing about a noon sight is that you get both lat., and long., giving you a pretty decent fix instead of just a line of position.

    One noon sight = three star sights. And, in addition, a noon sight is easier to reduce.
    Schooner captains love to get blown offshore!

  7. #42
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    Olympia, WA, USA
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    Default Re: Sextants

    Lunars are not skills building....unless you think learning math begins with Integral calculus or other supposedly higher math
    I meant "skills building" more in the sense of learning to handle the sextant. Time spent moving the mirrors around, learning how to work with the tool.

    As for the rest of your post, GilberJ --thank you. That's a lot of good information, especially for me, since I've only really played at celestial navigation, and only the most basic stuff at that.

    I have a nice Frieburger...
    I'll look one up.

    I just want to say that I really appreciate the way folks have taken my OP and expanded on it. There are a lot of relevant tangents (hah!) that have sprung from "what make of sextants do people like?"

    Alex

  8. #43
    Join Date
    Apr 1999
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    Now, there's a long story...
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    Default Re: Sextants

    +1 on the Freiburger...
    Heute ist so ein schöne Tag...

  9. #44
    Join Date
    Dec 2010
    Location
    Ohio USA
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    Default Re: Sextants

    There are 3 things you need to learn
    1. How to use the sextant and get a good measurement.
    https://www.youtube.com/watch?v=PK6v-833dkc
    2. How to read the Nautical Almanac
    http://navsoft.com/2014_Almanac.pdf
    3. How to do the calculations.
    Nav01 Noon Sight Example Both Longitude and Latitude
    https://www.youtube.com/watch?v=w75E2SmV53g

  10. #45
    Join Date
    Jun 2003
    Location
    Central Coast, Ca
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    17,577

    Default Re: Sextants

    I have mostly used a sextant sideways, taking bearings from landmarks and or buoys/lights for coastal navigation or piloting, never for celestial other than an excercise.

  11. #46
    Join Date
    Feb 2002
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    Shubenacadie NS
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    3,725

    Default Re: Sextants

    Horizontal sextant angles we call them in the RCN Canoeyawl.
    If one advances confidently in the direction of his dreams, and endeavors to live the life which he has imagined, he will meet with a success unexpected in common hours.
    -Henry David Thoreau-

  12. #47
    Join Date
    Jun 2003
    Location
    Central Coast, Ca
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    17,577

    Default Re: Sextants

    Yes, and a vertical angle can be used to note the distance to "the beach" using the height of a known landmark like a lighthouse. (Having small enough boats that mostly are no worries until you can see the bottom, I have never done that other than a practice)

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