Friends,
I am a true son of a son of a son of a sailor, coming from a line of sea captains out of New Bedford. My coastal boating adventures have always been within eyeball sighting of land or fixed marks, which made the use of a compass almost un-necessary. Growing up with the fog on Buzzard’s Bay in the summers of the 1960's though dictated that I, at the very least, knew which bearing to take in order to go from buoy to buoy amidst the perilous rock pile reefs. I’ve done some foolish seat-of-the-pants navigating once or twice, and I consider myself lucky to be alive to tell the stories – although I don’t tell them often, out of shame.
I love my technology, and have to say that the advent of affordable GPS units makes me a more confident skipper. However, I decided some time ago to attempt to learn, if not master the art of celestial navigation. It has now become an obsession. Not being an astute mathamagician makes this progression more than a simple exasperation. (How’s that for a Didereauxism!). I have been a teacher and professor for many years, so I’m considered relatively intelligent, but at the same time consider myself a slow learner. I’ve picked up a decent book, “Celestial Navigation in a Nutshell” and have learned that the nutshell is a pretty tough barrier. I’ve been shopping for a good deal on a decent sextant. That being said, I’d like to find someone who can mentor, who is willing to give me some pointers.
Any takers???
Celestial Navigation
Moderator: Jim Walsh
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Dan & Pat
- Posts: 107
- Joined: Mar 27th, '06, 18:59
- Location: CD 25 #282: "Play it Again Sam" Fort Lauderdale, FL -
- Contact:
Celestial Navigation
Madness takes its toll. Please have exact change.
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John Vigor
- Posts: 608
- Joined: Aug 27th, '06, 15:58
- Contact:
Dan and Pat:
It would be a very brave person who would offer to mentor a teacher and professor, even a confessed "relatively intelligent slow learner."
I, too, am a slow learner, but I lack relative intelligence, so when I wanted to do a spot of celestial navigation I bought a book called "Celestial Navigation for Yachtsmen." The author is a woman called Mary Blewitt.
My book, a 1964 edition, is 59 pages long and many of those pages are reproductions of tables and large simple diagrams for dumb sailors.
It is the simplest, most direct tutor on sextant navigation that I've ever come across. If I, with my limited capacity, could learn to find my way across the Atlantic thanks to Mary Blewitt, I am sure someone such as you, with reasonable intelligence, would find it no challenge at all--given time, of course.
The book is still available in updated editions but probably has accumulated many more pages by now.
Sorry I can't help you with a sextant, but e-Bay usually has a good selection.
Cheers,
John V.
_________________
From Vigor's Rules for Life:
8. Simon's Law: "Everything put together falls apart sooner or later."
It would be a very brave person who would offer to mentor a teacher and professor, even a confessed "relatively intelligent slow learner."
I, too, am a slow learner, but I lack relative intelligence, so when I wanted to do a spot of celestial navigation I bought a book called "Celestial Navigation for Yachtsmen." The author is a woman called Mary Blewitt.
My book, a 1964 edition, is 59 pages long and many of those pages are reproductions of tables and large simple diagrams for dumb sailors.
It is the simplest, most direct tutor on sextant navigation that I've ever come across. If I, with my limited capacity, could learn to find my way across the Atlantic thanks to Mary Blewitt, I am sure someone such as you, with reasonable intelligence, would find it no challenge at all--given time, of course.
The book is still available in updated editions but probably has accumulated many more pages by now.
Sorry I can't help you with a sextant, but e-Bay usually has a good selection.
Cheers,
John V.
_________________
From Vigor's Rules for Life:
8. Simon's Law: "Everything put together falls apart sooner or later."
Didereauxism!....love it!!! now to the?
Dan&Pat
Nutshell is good, I carry it onboard. BUT the one you NEED with it is called 'The Complete On-Board Celestial Navigator' by George G. Bennett (it is avail on Amazon for around $20-$30). With this book you DO NOT need an Almanac, it has its own, a seven year one that that presently goes through 2007(hence the price range).
Study the use of the sextant with Nutshell, go down to the shoreline at a time when the sun will be over the water and at least midway up. take a series of shots. Remember that the height of eye IS important, measure yourself with a cheap tape measure(they rust heh) or do it at home and stand at the or very near the waterline when you tke your shots. TIME set or make note of the exact seconds your watch is off with time standard(NIST do a search) is on the net and easy. Remember that 4 seconds of time equals a MILE in distance.
A series of shots is at least five taken with moderate speed and great care. Now you have you basic data.
Go home get on the net and get the online almanac which will give you the Almanac data you need for that day and time. Now do the arithmetic... using this method does require that you have a Site reduction tables for your latitude HO 249(air) works well enough.
Otherwise(and you should do this anyway) do all the examples in the Nutshell, not once but several times until it becomes boring.
When you are comfortable with all the above. THEN go to Bennetts book and you should have zero trouble.
Get proficient on land or an aircraft carrier before trying it on the smaller sailboats. When that time comes whistle again. There are tricks to all trades, and several on this board now a good number of them.
Just for grins if you are really, really, really into this stuff get Susan Howards book 'Celestial Navigation' from Mystic. Howard was the professor of such at the Mystic College or some such before being lost in the trainining ship capsize back in the 80's...but be forewarned she takes no prisoners and covers the subject so completely if you could pass the course you'd qualify as an Master Ocean Navigator in any Navy or Merchant Marine in the world.
Oh yeah, nearly forgot...the SEXTANT. I have several and used more, but the one I kept aboard was a Davis Mark 25. Yes, the yuppies sneer(but then they can't use a sextant anyways) they are very lightweight and ideal for using on small boats(those less than a tramp steamer size. Their accuracy is more than adequate and they are cheap. New around the $200-250 range and always around half that on eBay. Really, they are good instruments.
g'Luk
Nutshell is good, I carry it onboard. BUT the one you NEED with it is called 'The Complete On-Board Celestial Navigator' by George G. Bennett (it is avail on Amazon for around $20-$30). With this book you DO NOT need an Almanac, it has its own, a seven year one that that presently goes through 2007(hence the price range).
Study the use of the sextant with Nutshell, go down to the shoreline at a time when the sun will be over the water and at least midway up. take a series of shots. Remember that the height of eye IS important, measure yourself with a cheap tape measure(they rust heh) or do it at home and stand at the or very near the waterline when you tke your shots. TIME set or make note of the exact seconds your watch is off with time standard(NIST do a search) is on the net and easy. Remember that 4 seconds of time equals a MILE in distance.
A series of shots is at least five taken with moderate speed and great care. Now you have you basic data.
Go home get on the net and get the online almanac which will give you the Almanac data you need for that day and time. Now do the arithmetic... using this method does require that you have a Site reduction tables for your latitude HO 249(air) works well enough.
Otherwise(and you should do this anyway) do all the examples in the Nutshell, not once but several times until it becomes boring.
When you are comfortable with all the above. THEN go to Bennetts book and you should have zero trouble.
Get proficient on land or an aircraft carrier before trying it on the smaller sailboats. When that time comes whistle again. There are tricks to all trades, and several on this board now a good number of them.
Just for grins if you are really, really, really into this stuff get Susan Howards book 'Celestial Navigation' from Mystic. Howard was the professor of such at the Mystic College or some such before being lost in the trainining ship capsize back in the 80's...but be forewarned she takes no prisoners and covers the subject so completely if you could pass the course you'd qualify as an Master Ocean Navigator in any Navy or Merchant Marine in the world.
Oh yeah, nearly forgot...the SEXTANT. I have several and used more, but the one I kept aboard was a Davis Mark 25. Yes, the yuppies sneer(but then they can't use a sextant anyways) they are very lightweight and ideal for using on small boats(those less than a tramp steamer size. Their accuracy is more than adequate and they are cheap. New around the $200-250 range and always around half that on eBay. Really, they are good instruments.
g'Luk
Didereaux- San Leon, TX
last owner of CD-25 #183 "Spring Gail"
"I do not attempt to make leopards change their spots...after I have skinned them, they are free to grow 'em back or not, as they see fit!" Didereaux 2007
last owner of CD-25 #183 "Spring Gail"
"I do not attempt to make leopards change their spots...after I have skinned them, they are free to grow 'em back or not, as they see fit!" Didereaux 2007
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tartansailor
- Posts: 1527
- Joined: Aug 30th, '05, 13:55
- Location: CD25, Renaissance, Milton, DE
OK Lets Get Started
Overview of Celestial Navigation
There are two systems of celestial coordinates used by the Navigator: the
Celestial Horizon System and the Celestial Equator System.
The Celestial Horizon System locates a celestial body on the celestial sphere surface by the azimuth angle of the body and its altitude.
The Celestial Equator System locates the body on the sphere by the meridian angle (local hour angle) of the body and its declination.
The principal problem addressed in celestial navigation and sight reduction is converting the coordinates of one system to those of the other system.
You are solving the celestial triangle, the vertices being the elevated pole {the south pole if you are off the coast of Uruguay); the geographical position of the body; (the point where an imaginary line from the center of the body to the center of the earth hits the earth surface at a precise GMT time) and your position.
All right, lets see what we are working with.
After you get your sextant, please describe the 4 adjustable errors.
Now you just took a noon sight, please describe:
Apparent line of sight
Sensible Horizon
Geoidal Horizon
Height of eye
Celestial Horizon
Astronomical Refraction
Semidiameter
Parallax
Dip
Geometrical Horizon
Visible Horizon
Terrestial Refraction
Diderauxism
After we get the above squared away, we can look at Time, but only if you care to.
There are two systems of celestial coordinates used by the Navigator: the
Celestial Horizon System and the Celestial Equator System.
The Celestial Horizon System locates a celestial body on the celestial sphere surface by the azimuth angle of the body and its altitude.
The Celestial Equator System locates the body on the sphere by the meridian angle (local hour angle) of the body and its declination.
The principal problem addressed in celestial navigation and sight reduction is converting the coordinates of one system to those of the other system.
You are solving the celestial triangle, the vertices being the elevated pole {the south pole if you are off the coast of Uruguay); the geographical position of the body; (the point where an imaginary line from the center of the body to the center of the earth hits the earth surface at a precise GMT time) and your position.
All right, lets see what we are working with.
After you get your sextant, please describe the 4 adjustable errors.
Now you just took a noon sight, please describe:
Apparent line of sight
Sensible Horizon
Geoidal Horizon
Height of eye
Celestial Horizon
Astronomical Refraction
Semidiameter
Parallax
Dip
Geometrical Horizon
Visible Horizon
Terrestial Refraction
Diderauxism
After we get the above squared away, we can look at Time, but only if you care to.
Viam Inveniam Aut Faciam
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Warren S
- Posts: 254
- Joined: Jul 27th, '06, 21:22
- Location: s/v Morveren
Cape Dory 270 Hull #5
Washington, NC
On the subject of sextants....
I found this while researching sextants earlier this year: http://www.tecepe.com.br/nav/CDSextantProject.htm
I thought it was rather nifty!
I thought it was rather nifty!
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Warren S
- Posts: 254
- Joined: Jul 27th, '06, 21:22
- Location: s/v Morveren
Cape Dory 270 Hull #5
Washington, NC
And then there's THIS
I am limited to coastel work, but for the sheer joy of it, I may get this "starter kit": http://www.landfallnavigation.com/kcnb.html
the $$ seems right
the $$ seems right
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barfwinkle
- Posts: 2169
- Joined: Feb 6th, '05, 10:34
- Location: S/V Rhapsody CD25D
That is Just TOO Freaking KEWL
That is one neat project Warren.I found this while researching sextants earlier this year: http://www.tecepe.com.br/nav/CDSextantProject.htm
I thought it was rather nifty!
If I recall correctly, the author of 76 (or some odd days adrift) used pencils to make a sextant. This is WAY KEWL
Happy Thanksgiving
Bill Member #250.
A bit more
Just a personal preference for an easy to follow text: John Budlong's Sky and Sextant. It is long out of print, but easily found.
http://www.alibris.com/search/search.cf ... D21leGWImQ
This teaches using the Nautical Almanac and Pub. 249, Sight Reduction for Air Navigation. While there are many sight reduction tables and almanacs on the market, this combination is by far the easiest to use and produces more than sufficient accuracy for even the big ships. The USCG required use of Pub. 229, but for practical use it is overkill. Once/if you decide this is a fun hobby then you may want to expand your skills ito some of the other tables. Books that provide long term almanacs, or reduction tables in a few pages do more to add to the confusion of the beginner. I recommend sticking to the simplest books until you get comfortable.
As to sextants, start with one of the better plastic ones. Learn to properly adjust it and get lots of practice. The hardest part of celestial navigation is the mechanical skill with the sextant. Skill with a sextant is acquired the same way one learns to shoot a pistol - practice - practice and so forth. Over time you may want to move up to a metal sextant, with their heaver frame and better optics give better results.
Actual sight reduction is simple adding and subtracting. However, some of the long term almanacs and small reduction tables add to the arithmetic effort and increases to probability of error.
As a side note I taught myself back in the early 60's and have taught Celestial to yacht navigators and for use by Special Forces back in the pre-GPS dys. That said I only occasionally carry a sextant on the boat nowdays.
http://www.alibris.com/search/search.cf ... D21leGWImQ
This teaches using the Nautical Almanac and Pub. 249, Sight Reduction for Air Navigation. While there are many sight reduction tables and almanacs on the market, this combination is by far the easiest to use and produces more than sufficient accuracy for even the big ships. The USCG required use of Pub. 229, but for practical use it is overkill. Once/if you decide this is a fun hobby then you may want to expand your skills ito some of the other tables. Books that provide long term almanacs, or reduction tables in a few pages do more to add to the confusion of the beginner. I recommend sticking to the simplest books until you get comfortable.
As to sextants, start with one of the better plastic ones. Learn to properly adjust it and get lots of practice. The hardest part of celestial navigation is the mechanical skill with the sextant. Skill with a sextant is acquired the same way one learns to shoot a pistol - practice - practice and so forth. Over time you may want to move up to a metal sextant, with their heaver frame and better optics give better results.
Actual sight reduction is simple adding and subtracting. However, some of the long term almanacs and small reduction tables add to the arithmetic effort and increases to probability of error.
As a side note I taught myself back in the early 60's and have taught Celestial to yacht navigators and for use by Special Forces back in the pre-GPS dys. That said I only occasionally carry a sextant on the boat nowdays.
Jim Davis
S/V Isa Lei
S/V Isa Lei
Warre, don't ya jes' .......
Don't you just envy genius? !!!! What a neat idea. I may have yet another winter project! heh BTW he has some other good stuff on his homepage
http://www.tecepe.com.br/nav/
thanks
http://www.tecepe.com.br/nav/
thanks
Didereaux- San Leon, TX
last owner of CD-25 #183 "Spring Gail"
"I do not attempt to make leopards change their spots...after I have skinned them, they are free to grow 'em back or not, as they see fit!" Didereaux 2007
last owner of CD-25 #183 "Spring Gail"
"I do not attempt to make leopards change their spots...after I have skinned them, they are free to grow 'em back or not, as they see fit!" Didereaux 2007
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Neil Gordon
- Posts: 4367
- Joined: Feb 5th, '05, 17:25
- Location: s/v LIQUIDITY, CD28. We sail from Marina Bay on Boston Harbor. Try us on channel 9.
- Contact:
Re: Warre, don't ya jes' .......
It's the perfect lifeboat sextant. Don't forget the CD player!Didereaux wrote:Don't you just envy genius? !!!!
Fair winds, Neil
s/v LIQUIDITY
Cape Dory 28 #167
Boston, MA
CDSOA member #698
s/v LIQUIDITY
Cape Dory 28 #167
Boston, MA
CDSOA member #698
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Dan & Pat
- Posts: 107
- Joined: Mar 27th, '06, 18:59
- Location: CD 25 #282: "Play it Again Sam" Fort Lauderdale, FL -
- Contact:
information overload :(
Thank you one and all!
I knew I would find some, but never imagined so many Helpful recommendations in such a short span. I have to admit that I use this board for information more than I use Google.
The hand made project, using an old CD looks intriguing, although I can't understand how I would use my boat to make a sextant to sail it with
. It might be a great project for someone who's home bound for the winter, but here in South Florida the only thing we do to winterize our boats is to add a little air to the trailer tires when the temperatures drop down into the 60's or 70's (not yet though!), and maybe get rid of the shorts and bring a sweater aboard.
The terms and concepts are starting to sink in, and I have been reading and re-reading the book to get the basic concepts down. I'm only 3 miles from Fort Lauderdale, Hollywood, and Dania Beaches, so this will give me a good reason to get down to take horizon sightings early in the day. I will just have to try and concentrate on the celestial bodies and try and ignore the scantily clad out of town visitors strewn all over the sand.
I've been scanning e-bay for a while now, but much of the junk on there is 'reproductions' or else the bidding is way out of my league. I've been to dozens of websites, and have come to understand the differences in accuracy offered by different types, and the Mark 25 or Mark 15 seem to be what I'll be getting.
I've copied and printed all of your comments and promise to keep you posted.
Dan
I knew I would find some, but never imagined so many Helpful recommendations in such a short span. I have to admit that I use this board for information more than I use Google.
The hand made project, using an old CD looks intriguing, although I can't understand how I would use my boat to make a sextant to sail it with
. It might be a great project for someone who's home bound for the winter, but here in South Florida the only thing we do to winterize our boats is to add a little air to the trailer tires when the temperatures drop down into the 60's or 70's (not yet though!), and maybe get rid of the shorts and bring a sweater aboard.The terms and concepts are starting to sink in, and I have been reading and re-reading the book to get the basic concepts down. I'm only 3 miles from Fort Lauderdale, Hollywood, and Dania Beaches, so this will give me a good reason to get down to take horizon sightings early in the day. I will just have to try and concentrate on the celestial bodies and try and ignore the scantily clad out of town visitors strewn all over the sand.
I've been scanning e-bay for a while now, but much of the junk on there is 'reproductions' or else the bidding is way out of my league. I've been to dozens of websites, and have come to understand the differences in accuracy offered by different types, and the Mark 25 or Mark 15 seem to be what I'll be getting.
I've copied and printed all of your comments and promise to keep you posted.
Dan
Madness takes its toll. Please have exact change.
Two comments
1. You are right about the "reproductions" They are dubious for use as a wall decoration and most are improperly assembled to start with.
2. Celestial navigation is a process of navigating by the observation of "heavenly bodies", just know which one you are observing.
2. Celestial navigation is a process of navigating by the observation of "heavenly bodies", just know which one you are observing.
Jim Davis
S/V Isa Lei
S/V Isa Lei
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Sailing Soldier
- Posts: 59
- Joined: Apr 16th, '05, 09:34
- Location: Bristol 32 #15
formerly CD 28 #177
Courses?
I have been wanting to take a celestial nav class over the winter. Anyone know of a class being conducted in the RI/MA/CT area?
I'll probably order Landfall Navigation's "kit" with the Davis sextant. Seems hard to beat.
Capt. John
CD 28 #177
"Liberty"
RI
I'll probably order Landfall Navigation's "kit" with the Davis sextant. Seems hard to beat.
Capt. John
CD 28 #177
"Liberty"
RI
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CruiseAlong
- Posts: 140
- Joined: Mar 2nd, '06, 16:27
- Location: CD31, "KAUNIS", #45
Seaford, VA - Contact:
Celestrial Navigation
One of the most interesting celestrial navigation web sites is Omar Reiss's.
http://www.tecepe.com.br/nav
I have the electronic version (download) of Navigator 4.5 ($35) and it is super. There is also Navigator Light which is free. Navigator provides you will a printable 3-day daily sheet, star finder, automatic line of position calculator and plotting, fix position calculation, etc. etc. etc. quite the program....love it....super for the novice and pro since you can develop your sextant skills while knowing what the right answer is for comparison.
Anyway, I would be happy to mentor you through the learning process to get you started. We could take this on a weekly web lesson method. You need the following:
1. Computer to read some web site location explainations of celestrial navigation.
2. A plastic sextant....take a look at http://www.starpath.com for a description of the Davis line. If you think you are already serious about keeping up in the future, you may want to consider the Mark 15 or 25. The 25 has full horizon (beam convergency) which is much easier to learn on. Ebay has all of these regularly listed in very good condition for ~1/2 new price.
3. A good accurate digital watch like a CASIO
4. A view of the sea horizon facing south. If not then one needs an artifical horizon horizon which is also a Davis or a bucket of water whose surface is protected from the wind ripples
5. HO 249 Air Navigation Tables Volume 1 if you are below 40 degrees latitude home location, Volume 2 if you are located above 40 degrees latitude. If you do not have these then we could work from practice 249 table sheets that I would provide you....
I have been sailing for about 26 years. Have taught Aux Coast Guard Sailing and Seamanship and Navigation courses. My sextant "collection" is a Davis 25, Astra IIIb, Army Air Force WWII A-10A Bubble sextant, and a WWII Pioneer AN5851 Bubble Sextant. So I do star shots as well with some older bubble sextants. We would start with noon sun shots, then moving on to afternoon sun, then fore noon sun shots. Then we will put it all together for developing a fix and running DR. Let me know if you are interested....Dana
http://www.tecepe.com.br/nav
I have the electronic version (download) of Navigator 4.5 ($35) and it is super. There is also Navigator Light which is free. Navigator provides you will a printable 3-day daily sheet, star finder, automatic line of position calculator and plotting, fix position calculation, etc. etc. etc. quite the program....love it....super for the novice and pro since you can develop your sextant skills while knowing what the right answer is for comparison.
Anyway, I would be happy to mentor you through the learning process to get you started. We could take this on a weekly web lesson method. You need the following:
1. Computer to read some web site location explainations of celestrial navigation.
2. A plastic sextant....take a look at http://www.starpath.com for a description of the Davis line. If you think you are already serious about keeping up in the future, you may want to consider the Mark 15 or 25. The 25 has full horizon (beam convergency) which is much easier to learn on. Ebay has all of these regularly listed in very good condition for ~1/2 new price.
3. A good accurate digital watch like a CASIO
4. A view of the sea horizon facing south. If not then one needs an artifical horizon horizon which is also a Davis or a bucket of water whose surface is protected from the wind ripples
5. HO 249 Air Navigation Tables Volume 1 if you are below 40 degrees latitude home location, Volume 2 if you are located above 40 degrees latitude. If you do not have these then we could work from practice 249 table sheets that I would provide you....
I have been sailing for about 26 years. Have taught Aux Coast Guard Sailing and Seamanship and Navigation courses. My sextant "collection" is a Davis 25, Astra IIIb, Army Air Force WWII A-10A Bubble sextant, and a WWII Pioneer AN5851 Bubble Sextant. So I do star shots as well with some older bubble sextants. We would start with noon sun shots, then moving on to afternoon sun, then fore noon sun shots. Then we will put it all together for developing a fix and running DR. Let me know if you are interested....Dana
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barfwinkle
- Posts: 2169
- Joined: Feb 6th, '05, 10:34
- Location: S/V Rhapsody CD25D
Very Interesting Dana
I would like to know if you could do this to perhaps a group? I now the bacis concepts and have completed/read one of the above mentioned books, but it has been a while.
I have everything I need, except I'll have to use the bucket of water, and I dont know if it would work here in Oklahoma without my being at the lake. We have a great view to the west and somewhat less to the south!
Would the bucket of h20 work?
TIA
I have everything I need, except I'll have to use the bucket of water, and I dont know if it would work here in Oklahoma without my being at the lake. We have a great view to the west and somewhat less to the south!
Would the bucket of h20 work?
TIA
Bill Member #250.