Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 26-02-2007, 18:35   #1
Registered User

Join Date: Feb 2007
Location: Land locked
Boat: NONE yet
Posts: 114
Sextant

In hopes that someday I can cut loose of the everyday and spend the rest of my life sailing and cruising the oceans of the world. I have been reading all the helpful information that you (the experienced cruisers have posted here). I also want to teach myself celestial navigation. I have been looking for a sextant that I can start practicing with. I have found many websites that sell them and then decided to check ebay as well. Now on ebay I have found several that claim to be working reproductions of antiques. Here lies the problem the ones that I find on ebay are selling for less than $100, my question is would one of the under $100 ones be sufficient or would I just be throwing my money away. Here is a prime example of the ones under 100 bucks. eBay: 6in Brass ROSS LONDON Working Rack Pinion Sextant w Box (item 110096036837 end time Mar-02-07 18:19:52 PST)

Any input would be great.
__________________

__________________
charley is offline   Reply With Quote
Old 26-02-2007, 18:53   #2
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Charlie,

That would be just throwing money away. They might look good in pics, but they're unsuited for real celestial navigation.

However, you can find used plastic sextants for under $100. They work just fine, and you can even use them at sea for real navigation.

A good quality metal sextant goes for a minimum of about $300 used. The better ones, like Plaths, will cost about twice that.

Bill
__________________

__________________
btrayfors is offline   Reply With Quote
Old 26-02-2007, 18:59   #3
Registered User

Join Date: Feb 2007
Location: Land locked
Boat: NONE yet
Posts: 114
Thanks Bill that is exactly what i needed to know.
__________________
charley is offline   Reply With Quote
Old 26-02-2007, 20:21   #4
Registered User
 
NoTies's Avatar

Join Date: Nov 2005
Location: Vanuatu
Boat: Whiting 29' extended "Nightcap"
Posts: 1,378
Images: 2
I've got a Davis plastic model. Very high quality and any disadvantage from distortion due to heat etc. seems to be outweighed by the fact it is light and very easy to hold steady compared to metal. Bought on Ebay for $200
__________________
Pete

Positively, socially deviant.
NoTies is offline   Reply With Quote
Old 26-02-2007, 20:33   #5
Senior Cruiser
 
SkiprJohn's Avatar

Cruisers Forum Supporter

Join Date: May 2006
Location: Kea'au, Big Island, Hawaii
Boat: Cascade, Sloop, 42 - "Casual"
Posts: 14,192
Hi Charley,
I've been trying to trim down on my Davis plastic sextant collection. If you are interested you can send me a private message and I can give you an especially good deal on either a Mark 25 or Mark 15. Your choice.
Kind Regards,
JohnL
__________________
SkiprJohn is offline   Reply With Quote
Old 26-02-2007, 21:08   #6
Marine Service Provider

Join Date: Apr 2005
Location: Salish Sea
Boat: Tayana 37
Posts: 243
Okay, charley, just know this is coming from a guy who carries a sextant that he does not know how to use -- there is an instruction booklet in case of emergency! Though I do have good intentions. First mate and I plan to one day pull it out and teach ourselves how to use it.

Most people I know never, ever use their sextants. Even a sailor who taught celestial navigation, admitted to me he never takes his out of the box. He told me not to bother, but I got one anyway, as much because I was curious than thought I would really need it.

Buy a cheap plastic one. But you can't have mine. I might need it one day. Have fun
__________________
jimbim is offline   Reply With Quote
Old 26-02-2007, 21:22   #7
Registered User
 
blahman's Avatar

Join Date: Jun 2006
Location: Charlotte Harbor, FL
Boat: Westsail 32
Posts: 301
Images: 50
I suggest you keep your eyes peeled on ebay for a used Tamaya, Plath or Astra. Plastic sextants are generally more susceptible to errors due to temperature and handling.
In addition, they are harder to hold steady due to wind and seaway because of their light weight. Many people mistake the lightness for being easier to control, but it just makes it more susceptible to movement. Basic physics; heavier objects take more effort to move. Though they can be heavy when you're first learning to shoot, you'll eventually be able to shoot quick enough to not notice, and will appreciate their heft when it's blowing.

I have an Astra IIIB, purchased new for $480.

Best of luck,
Aaron N.
__________________
blahman is offline   Reply With Quote
Old 27-02-2007, 06:19   #8
Registered User

Join Date: Apr 2006
Location: Galveston
Boat: C&C 27
Posts: 724
Charley, I have one of the small brass sextants that works great as a decoration in my office. On board I use a Davis MK15. There is another thread SkipprJohn started months ago concerning sextants. You may want to search for it. For simply knowing lat-lon a sextant may not be of much advangtage, GPS units are too quick and too cheap. But that is not to say sextants are not vaulable for navigation. Today, a sextant may have more value as a costal navigation tool than as a voyaging tool. I can't hold anything very steady on the deck of the boat so my only complaint with the Davis is that the arm can feel sticky if not properly lubricated. In any case consider buying an inexpensive one to study with. You may want to check out this link.

CD-Sextant - Build your own sextant

This may not be any better than the decorative sextant.
__________________
Pura Vida is offline   Reply With Quote
Old 27-02-2007, 12:09   #9
Registered User

Join Date: Feb 2007
Location: Land locked
Boat: NONE yet
Posts: 114
Like any good peice of equipment you get what you pay for. I thought it was to good of a price to be any good just thought that I would check. I did find two real good ones on ebay that I hope doesn't go over $200. Will see! Thanks for all the helpful advise.
__________________
charley is offline   Reply With Quote
Old 27-02-2007, 12:25   #10
Senior Cruiser
 
SkiprJohn's Avatar

Cruisers Forum Supporter

Join Date: May 2006
Location: Kea'au, Big Island, Hawaii
Boat: Cascade, Sloop, 42 - "Casual"
Posts: 14,192
For anyone who carries a sextant aboard and figures they can study up on it if an emergency arises. You may want to carry your own dental tools and surgical instruments too.
You could use the little mirrors for signalling.
Just get a couple of simple books on celestial navigation and see if you can piece it together in a day or two. Using a sextant is no big mystery but it is not a snap either.
Kind Regards,
JohnL
__________________
SkiprJohn is offline   Reply With Quote
Old 27-02-2007, 14:14   #11
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
SkipperJohn makes a good point. Celestial navigation isn't rocket science, but it isn't a good idea to try to learn it while at sea.

Vivid in my memory is the case of the Trans Atlantic sailor who, having left the Canary Islands in November for Barbados, had planned on learning celestial navigation on the way. This was in the 70's, way before GPS.

At the time, I ran the TransAtlantic MM Net (daily at 1300Z on 21400 KHz) from my station in Morocco (CN8CW), aided by Ian in Barbados (8P6HZ).

To make a long story short, I was able to feed him sight reduction info daily via the net, using a programmable HP65 calculator in my ham shack. He would just take the sextant sight, his crew would say, "NOW" into the microphone, and I did all the calculation work. I knew his DR, approximate speed, etc. and, of course, when I heard the "NOW" I knew the Greenwich time of the sight. He'd feed me the sextant reading (Hs), I'd apply the corrections and calculate the azimuth, intercept, and most probable postion.

This was an interesting and bizarre situation, but is NOT RECOMMENDED for celestial navigation wannabe's. As they say, don't try this at home!

Bill
S/V Born Free
WA6CCA
__________________
btrayfors is offline   Reply With Quote
Old 27-02-2007, 16:59   #12
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,043
Charley, there are a lot of thieves on eBay and several of them are selling ornamental sextants, usually brass and usually London, either accidentally or perhaps intentionally failing to make clear that what they are selling is an ornament--not an instrument.

Caveat emptor. A good used metal sextant (Astra, ARES, Freiberger, Tamaya, any "Plath" company, etc.) is going to sell for good money and if you arent' familiar with sextants and don't know how to inspect one for damages, I'd suggest either sticking to a reputable vendor, or buying one of the less expensive metal ones, new, from a reputable vendor.

The plastic ones are plenty good enough for learning, in fact they might be better because in order to get good results you will have to check the index error every time you use it--reinforcing that habit.

There are pros and cons to all of them, and pretty much everything can be considered both good and bad, i.e. "light" vs "heavy". Any of them, even the cheap Davis, will help you make landfall if everything else fails. The better models with more precision, if you can take advantage of it, are worth their higher prices more if you can afford to invest in an intellectual exercise, i.e. if you really want to compete with yourself to see if you can get a fix within two miles (considered a tight fix from a small boat at sea) instead of five or ten miles.

Some planetariums and Power Squadrons give celestial nav classes, if you can track one down the instructor may be willing to talk to you and give you some hands-on time before you buy anything.
__________________
hellosailor is offline   Reply With Quote
Old 27-02-2007, 17:15   #13
Senior Cruiser
 
SkiprJohn's Avatar

Cruisers Forum Supporter

Join Date: May 2006
Location: Kea'au, Big Island, Hawaii
Boat: Cascade, Sloop, 42 - "Casual"
Posts: 14,192
Way to go Bill.
Plastic vs metal sextants. IMHO Plastic is ok as long as you check your horizon each time you use it. Metal sextants don't need to be checked each time but it is a good idea anyway. Other than that you'll be just as accurate with either. Best to use a plastic one on a rocking boat because if either is dropped, metal or plastic, there is a good chance that the metal one will be unusable after you pick it up. They don't bounce as well.
I don't take my Astra IIIB on deck if it is nasty weather. I take the plastic Davis. My Davis Mark 25 got me from Hawaii to the Straits of Juan de Fuca within 9 miles of the center of the Straits with the last three days just being dead reckoning because of fog. I would not have done any better with an expensive metal sextant. GPS wasn't invented yet. Satnav was way too expensive.
The point I'm trying to make is that if you want to practice you'll be more apt to carry a cheaper plastic sextant up on deck than a very expensive metal one so you'll practice more. Your sights won't be any more accurate with the metal one. However, metal sextants are prettier and just the weight of them in your hand feels good.
I learned on Davis plastic sextants and have a good deal of respect for them and you can tune any error out of them as well as you can a metal sextant.
Kind Regards,
JohnL
__________________
SkiprJohn is offline   Reply With Quote
Old 28-02-2007, 06:44   #14
Registered User
 
Raven's Avatar

Join Date: Apr 2006
Location: Lake Champlain, Vermont
Boat: Pacific Seacraft Crealock 34 - "Raven"
Posts: 213
Images: 6
Tania Aebi's book, Maiden Voyage, about her singlehanded circumnavigation in the late '80's is a good read. In it, she writes of trying to learn celestial navigation after setting sail from NY, en route to Bermuda on the first leg of her journey. (I believe she had along her dad's correspondence course materials on the topic.) She was unable to make it all work and ended up finding Bermuda through a combination of intuition, luck and an a.m. directionfinder. It wasn't until she was in the Pacific that she discovered that her sextant was damaged and eventually got the navigation sorted out.
__________________
Kevin Rose
Pacific Seacraft Crealock 34 - Raven
Burlington, Vermont
Raven is offline   Reply With Quote
Old 28-02-2007, 10:40   #15
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,043
Raven, I think she commented on that in one of her articles. Her exact words were something along the lines of being extremely lucky to be alive, because she couldn't figure out the sextant and celestial and she could have easily missed Bermuda (her first landfall) entirely.

Personally, I find the sextant itself to be easy, and the tables/calculations to be a great way to screw up. So I've got nav software in my Palm, which is the most loyal and faithful silicon critter ever to have been on my staff.<G> Easy to keep it warm and dry, too.

If nothing else, a cheap old obsolete Palm makes a great double-check on your manual calculations, when the answers aren't the same, it is time to run the numbers again and find out why.
__________________

__________________
hellosailor is offline   Reply With Quote
Reply

Tags
sextant

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Celestial Navigation Help Needed Loose Ends Navigation 67 10-11-2011 13:19
Davis Mark 15 Sextant rsn48 Navigation 16 06-01-2009 21:52
Celestial Navigation SkiprJohn Navigation 45 29-12-2008 23:15



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 09:17.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.