Celestial Navigation, part2: Sextant

[Apex]

Based on the previous thread, I wonder about the various sextants out there.

Besides the Plastic Davis version, what other sextants can actually be used for some resemblance of navigation?
Given the accuracy of GPS and not subscribing to the doomsday theorists of GPS hack, part two of finding a sextant is reallocated to "decor" duty following giving up on CN.

:O)

 

[Brian D]

I have the Davis Mark 25 and I purchased it from Celestaire in 2009. SBO also sells the Davis version sextants. Celestaire has metal sextants but man are those things expensive. Probably more accurate than the hard plastic ones.

 

[okawbow]

If you have a plastic protractor and a pencil, along with a book that tells you Greenwich noon times for a given date; it's possible to determine your longitude to within 60 miles or so, by taking a noon sight. You can then get your latitude by measuring the angle of the North Star to the horizon. Many have crossed oceans with such simple navigation, and a chart and compass.

Even a cheap plastic sextant will be far more accurate. However, it takes years to get better than 10 mile or so accuracy for most people.

 

[justsomeguy]

Probably more accurate than the hard plastic ones.

Must be because they cost more, huh?

 

[bgary]

I learned on - and carried as a backup - a Davis plastic sextant for years. They will do the job, albeit not as accurately as an "instrument-grade" device. The main thing is that the molded detents and indicator markings are not nearly as precise. But there is a lot of utility in one, both for learning and for general use.

I wouldn't hesitate to recommend one for general use. But I also would expect to be "pleasantly surprised" if I got better than 1/4-minute (~15 mile) resolution on my LOPs.

 

[Brian D]

My issue (and sorry to go off topic) is the horizon. Living in a hilly area we don't really have a horizon to speak of. I don't want to use an artificial one like the Davis. So, being a musician, I realized I had mic stands with booms. Created my own by raising the stand to about eye height and leveled the boom. Got me a horizon now. LOL. I also emulated being on the boat by lowering the boom horizon about few feet. But that really doesn't matter because the true horizon is so far away that parallex does not come into play. Oh the fun of using the sextant again.

 

[heritage]

Brian, you could try one of these: http://www.landfallnavigation.com/b...m_medium=shopping+engine&utm_campaign=froogle

 

[justsomeguy]

This plastic versus metal accuracy question reminds me of woodworkers' obsessions over the justifications for spending copious quantities of money on a "square" square.

A square square is square, no matter what it might have cost.

 

[Brian D]

Brian, you could try one of these: http://www.landfallnavigation.com/bubblehorizon.html?cmp=froogle&kw=bubblehorizon&utm_source=bubblehorizon&utm_medium=shopping+engine&utm_campaign=froogle

Thanks! Yeah, I saw that when I was searching on DIY Artificial Horizons. Then I thought why not just add a small bubble level. Then it occurred to me that I have a microphone stand with a boom. Just move the boom to eye height and make it level and there is your horizon. Cost me $17 and now I have two uses for it. LOL

 

[kloudie1]

One of these works for practice. https://www.celestaire.com/sextant-accessories/davis-artificial-horizon-detail.html
I used a swimming pool to practice when I learned many years ago. Had a Davis Mark 25 that worked OK but ya had to practice with it a lot because it could be distorted by hand pressure from holding it.. Once ya learn what affects it, it works pretty well. It was used on a crossing to Mexico back in 1989 before GPS, but with LORAN really calling the shots. I lost it back in 2001 when the house burned and I never replaced it .. just carry a couple of GPS's now.