Sextants

[SV_Harbinger]

I'm looking to getting a new "working" sextant. The one I have is an heirloom and quite old, I'm the 5th generation to have it and I learned on it from my grandfather, but keeping it in "active service" (mostly just practicing and comparing against GPS) I worry something may happen to it.
So here is where any of the other celestial nerds on here come in.
I was looking at a model from Davis Instruments, mk 15 to take it's place. Whens to "modern" sextants, I'm a bit lost and I have reservations about the plastic frame, particularly in temperature changes (as it heats or cools, wouldn't it warp slightly until it stabilizes? And how would I know it's stabilized)
Any advice, even if it's run away from the Davis would be greatly appreciated and if it is to avoid that model what would you recommend?

[Compass790]

I dont know about Davis but I can only say that my celestial nav instructor said avoid the plastic ones for exactly the reason you suggest.I hope that someone with practical experience can chime in with the accuracy differences tho.
I do have a plastic for a spare as I'm cheap but if the difference was say 5 miles I'd regard that as acceptable

[El Pinguino]

Try and find a Zeiss Freiburger... about $500 or a Zeiss Freiberger Yacht.. https://www.ebay.com.au/itm/Yacht-Se...UTpk:rk:1:pf:0

They seem to be getting scarce...

[KnotToday]

www.stanleylondon.com

Found this months ago. Prices range from $200 to $2200. Otherwise lost here...

[gjordan]

I used 2 plastic sextants to cruise the Pacific. The Davis 15, refered to as a lifeboat sextant was OK for sun sites but a little hard to get used to the way of reading the arc. For stars or planets, it was completely useless because it didnt have a scope to magnify the low light. That was my backup (@ $15) to my $25 Ebbco plastic sextant that I used for sun, stars, planets and moon. It worked fine but the accuracy was not spot on. Some of my pinwheels were a bit big. Of course from the deck of a 26 foot boat I really didnt expect pin point accuracy. I bought a nice Tamaya 3/4 size just about the time GPS came down in price so I didnt use it much and later lost it in a fire. I recently bought a Davis 25 to get back up to speed with celestial and keep for the day GPS or my electrics go bad. Sorry for the long answer. The short answer is YES, I would use a plastic sextant but not a 15 because of the lack of light gathering. Just my opinion. ____Grant.

[evm1024]

The Davis Mk15 or Mk 25 both can be useful and accurate enough for many needs.

The Mk 5 is the lifeboat sextant and is, well a lifeboat sextant....

New Mk15 or 25 list for $255 but I'm sure that you can find new at a discount. Used they can be found for less than $100. I did pick up an Astra III B NIB (new in box) for about $400 - So if you want one of those bide your time and keep looking.

I used a Mk15 for a celestial nav class I took and my sights were in accurate enough to pass the sight requirements. The instructor was actually quite impressed with its performance. And for less than $100 a good deal.

One thing to remember is that with work you can get a fix in the low miles of accuracy but you don't use celestial fixes for piloting. And sooner or later you will be piloting when you are approaching an Island. The bigger the island the further out you are piloting.

Anyway, bottom line I can recommend the Mk 15 for a working sextant. Plus or minus 5 miles is easy, plus or minus 3 miles is common ....

[GrowleyMonster]

No plastic for me, thanks. The nicer Davis ones do have a following, but at current prices I don't think you get your money's worth.


Best bang for the buck IMHO is a new Astra IIIb or else a good used Plath, which is what I currently have. Can't afford either one? Old Plaths can be found on fleabay for as little as $300 in quite usable condition. Of course there are also some basket cases being misrepresented as good classic sextants so you takes yer chances. Try Celestaire.com for Astra or Davis instruments. Their prices are pretty much rock bottom.


A new Plath is the bee's knees. But unless you REALLY use it or you are just a huge fan of celestial nav, I question whether or not you get your money's worth. They are WAAAAAY not cheap. I would only have one if I won the Powerball.

[svHyLyte]

A top source for celestial navigation information and equipment on-line is Celestaire. As GrowleyMonster commented, the Astra IIIB is an excellent choice, with the "Professional" model comparable to much more costly units. With that, IMHO the marginal benefit of added expense is unjustified. Note, however, just because your current sextant is "old" doesn't seem like a particularly good reason to replace it. After all, they don't really "wear out" unless they haven't been cared for, No?

FWIW...

[SV_Harbinger]

Hylyte, if they do wear out it must take an exuberant amount of time, at about 150yrs old it still gets me to within 3 miles and the scale is still perfectly readable. But that is kind of the reason why I want to semi-retire it, I don't want anything to happen to it, but it's not going to be put in a box ashore either.
Now the Astra IIIb seems seems to be the direction I'm leaning toward, it's aluminum, which I trust more than the plastics and seems to have a pretty good following, the price point isn't terrible ($650US) either. Seems to me like this may be the road I'll be going down but I still want to look into it more, my mind isn't made up yet lol

[gjordan]

OOPS, I got the MK 3 lifeboat sextant confused with the MK 15. I dont think heat is much of a problem unless you leave the instrument laying in the sun. The length of time that a sextant is out of the case is relatively short so it should not change temp very much. As I said, I lost my good Tamaya in a fire but ran across the old lifeboat MK 3 a while back. I sent to Davis for a new set of mirrors (I think it was less than $10) and they would not fit. They have changed things over the years. The lifeboat sextant is good for just what it is called. If you are in a lifeboat and have the little bit of information needed for a noon site , it will do the job but any sextant without a decent scope will be tough or impossible to get evening star sites. I doubt that will matter in an emergency. I dont know if Ebbco still makes low cost sextants anymore, but I was pleased with the one I had (also went up in the fire). I recently bought a Davis MK 25 for $100 and that will do anything I want for not much money. ____Grant.

[conachair]

You could save a search on ebay and see what comes up over a few weeks, I got a Freiberger for couple hundred UKP, as good as I'll ever need. Nice to have onboard even if very unlikely that it will ever be used 'for real' .

[gjordan]

Just another comment about doing noon sites. If you are actually planning on using a sextant for anything more than an emergency, I would highly recommend NOT LEARNING HOW TO DO A NOON SITE. The reason I say this is that many of the cruisers that I met before the age of GPS learned to do a noon site and patted themselves on the back and that was as far as there skill went. It is not that much more knowledge to do all of the celestial bodies and if you have spent several days with cloud cover in the midday you will be glad that you can take shots anytime of the day. Also for day time sights it is good to cross the sun and the moon (when available). Just my opinion! ____Grant.

[SeanPatrick]

Another vote for the Astra IIIb from Celestaire. They are the best value for the money. Very good quality.



The Davis plastic sextants are okay ... if you don't mind doing index error checks before and after every sight. They are affected by temperature changes, even in a very short time span. I've even noticed mine change readings if I simply squeeze the handle too hard. Plastic will flex much more readily than metal, of course. Don't get me wrong - you can sail around the world with one. It just takes more care than using a metal sextant.


Oh, and stay away from "Stanley of London" if you want anything more than a non-functioning ornament for your desk.

[GrowleyMonster]

Originally Posted by SeanPatrick

Another vote for the Astra IIIb from Celestaire. They are the best value for the money. Very good quality.



The Davis plastic sextants are okay ... if you don't mind doing index error checks before and after every sight. They are affected by temperature changes, even in a very short time span. I've even noticed mine change readings if I simply squeeze the handle too hard. Plastic will flex much more readily than metal, of course. Don't get me wrong - you can sail around the world with one. It just takes more care than using a metal sextant.


Oh, and stay away from "Stanley of London" if you want anything more than a non-functioning ornament for your desk.

ROTFL! I forgot to mention that! There are a lot of SSO's (Sextant-Shaped Objects) listed on Fleabay. If it is not a Plath, Frieberger, Tamaya, or other well known maker, research carefully before you pull the trigger. I bought a pocket sextant (yes, there is such a thing and surprisingly enough, sort of useable) that came from a London estate sale and not from India. I thought maybe it would be the real deal but it was a total complete joke. Sent it back.


In Belize I once met a retired Royal Navy guy who regularly sailed his wood sloop across the Atlantic, his only navigation instruments were an AM/SSB portable radio, (useful as RDF as well as for time ticks) Timex stem wound wristwatch, (why Timex? I don't know, but he loved the brand) a plastic sextant which I don't remember but was probably a Davis, hand drawn charts, homemade triangles, a yardstick, and carpenter's pencil. (doesn't roll) Said he never missed a landfall by much. About as basic as you would want to get. He said he aiways tried to make his observations in the shade, even if he had to come about to do it. I wish I could remember his name now. Anyway just because I wouldn't have a plastic sextant doesn't mean that they are "no good", just that they have limitations that need to be considered and allowed for.



I do think a decent metal sextant will make you a better navigator, though. Reducing instrument based errors will make your own computational and observational errors more obvious, allowing you to correct them and learn to not make them.

[gjordan]

I just looked thru about 300 listings for sextants on Ebay. 99% were decorative junk with a few real sextants that seemed overpriced. I was surprised to see only 1 Astra. Many of the decorative toys seemed to be advertised as real working sextants. Buyer beware! The best prices seemed to be from the breakers yards in India. I wonder about any type of guarantee from a wrecking yard? After I bought my Davis 25, I did see some good deals on Craigslist for metal sextants. I would suggest checking Craigslist regularly,up and down both coasts. Something good will come up. ____Grant.