Thinking caps on

michaelF
28th October 2010, 15:08
Hi all,
just checked the batteries in my sextant , still in good condition and working although a little flat since last used in 1983.Yes i have replaced , but i digress.

This got me to thinking .

Morning sight and az by ABC tables , noon lat taken , both run up/or back to 1200 and transfered to plotting sheet , fix obtained ,job sorted.

The 1200 fix can be calculated by plane and parallel sailing formulae or traverse tables used instead of plotting , but this is class room stuff.

In the real world i used d.lat x c correction to find the correction to apply to the 1200 DR longitude to obtain corrected longitude.

My question is , where did i get this formula from , was it in norries ? or how was it derived ?

mike

ps i have no tables to check from

peter3807
28th October 2010, 23:52
Michael,

You have really depressed me, I last picked up a sextant in 1977. I loved navigation with a passion. Moon, stars any time of day I would have a go. My sextant didn't have batteries. Thought I could crack this but having dragged out all old navigation books I have picked up over the years I now realise that I have lost it all. This despite having studied OU maths courses. It makes you realise that spherical trig and celestial navigation is a unique discipline which is being lost. It is not a new thing, I recall meeting up with an old school friend 3 years after I left school at 16 and went to sea. I had just completed my first trip third mate. He had passed A levels and was studying maths at university. I mentioned spherical trig and the haversine formula, he looked at me as if I was stupid, hadn't a clue what I was talking about.
Anyway, thanks for the kick up the ar*e, the books are out, now back studying real maths.

Peter

michaelF
29th October 2010, 00:11
Peter,
sorry for making you depressed, i agree with everything you say, the skill of navigation is being lost and forgotten.

There is a lot of stuff on the internet about this subject , mainly by people wanting to sell you books full of useless information , not really applicable to practical navigation.

I still can not find any mention of the formula d.lat x c correction ,
has anybody else heard of this or used it , i did for years .

mike

ps maybe i too have lost it

kewl dude
29th October 2010, 05:29
I was on a ship where the 1 A/E, a school ship graduate, bought a sextant in Japan and the 2nd mate instructed him on using it. When he was comfortable using it he took some sights and worked out our position out of the view of the bridge. Then showed up on the bridge when the master was there with a 24 inch pipe wrench and a tape measure.

He took sights with his pipe wrench and tape and wrote them down on a piece of paper and went in the chart room where he produced the position he had previously taken with his sextant. The bottom line is that the master wanted the 1 A/E to teach him how to do that.

But the 1 A/E demurred stating that he was taught how to do this in Engineering school and the master not having that background would never be able to grasp it.

Greg Hayden

RNW
29th October 2010, 07:32
Chinese navigators?

Anchorman
29th October 2010, 09:28
Peter,
sorry for making you depressed, i agree with everything you say, the skill of navigation is being lost and forgotten.

There is a lot of stuff on the internet about this subject , mainly by people wanting to sell you books full of useless information , not really applicable to practical navigation.

I still can not find any mention of the formula d.lat x c correction ,
has anybody else heard of this or used it , i did for years .

mike

ps maybe i too have lost it



Its in Burtons tables Mike.
If you PM me with your email address I will scan the page and send to you.
Regards.
Neil

michaelF
29th October 2010, 11:59
Neil ,
Thank you , thank you , thank you ,

i was begining to doubt myself .

will pm now

mike

Anchorman
29th October 2010, 14:36
Neil ,
Thank you , thank you , thank you ,

i was begining to doubt myself .

will pm now

mike

Email on the way Mike. Hope it is what you require.
All the best.
Neil

michaelF
29th October 2010, 14:39
Neil email received , thank you , perfect .

sanity restored

mike

michaelF
29th October 2010, 14:42
Ben Masey ,
thank you for confiming also . Well done the Bank Line.

mike

Klaatu83
29th October 2010, 18:29
I was on a ship where the 1 A/E, a school ship graduate, bought a sextant in Japan and the 2nd mate instructed him on using it. When he was comfortable using it he took some sights and worked out our position out of the view of the bridge. Then showed up on the bridge when the master was there with a 24 inch pipe wrench and a tape measure.

He took sights with his pipe wrench and tape and wrote them down on a piece of paper and went in the chart room where he produced the position he had previously taken with his sextant. The bottom line is that the master wanted the 1 A/E to teach him how to do that.

But the 1 A/E demurred stating that he was taught how to do this in Engineering school and the master not having that background would never be able to grasp it.

Greg Hayden

Sound's like an improvised astrolabe. Astronomers and Navigators used to use astrolabes to measure the angle of a body above the horizon before telescopes and sextants were invented (as in Columbus's time). In it's simplest form, it was was nothing more than a plumb line suspended from the axis of a quadrant. If I remember rightly, there used to be a chapter in Bowditch on "Lifeboat Navigation" that included instructions on how to make, and use, such an instrument in an emergency.

michaelF
29th October 2010, 19:06
Hi all,
just checked the batteries in my sextant , still in good condition and working although a little flat since last used in 1983.

As a postscirpt to this, the date on the original batteries is 83-01,
they have been in the spare battery compartment in the sextant box along with a sachet of silica gel , a tamaya ms 733 since new. Although not rechargable type i have read that they can be recharged , so what the heck i recharged them , now good for another 27 years.beat that?

mike

peter3807
30th October 2010, 01:33
Thanks all, found it.
Peter.

slick
30th October 2010, 07:20
All,
Speaking of GK of Spherical Trigonometry and Haversines etc, what were the papers for 2nd. Mates FG Exam., pre 1979
Principles of Navigation, Practical Navigation, Chartwork,was there Maths,, English anything else?
Incidentally I was wiling away a half hour watching an American Sitcom 'Malcolm in the Middle', and he, Malcolm enters in to an explanation of the uses of spherical trigonometry in Astronomy he has also referred to Kepler''s Laws of planetary motion, there were several blank looks around me.

Yours aye,

slick

michaelF
30th October 2010, 10:34
Slick,
between 68 and 79 i remember the subjects and pass grades changed quite a few times .

There was general ships knowledge , stability , physics? , meteorology , electronics , electricity , plus what you said .

Some subjects were merged together some dropped .

mike

Anchorman
30th October 2010, 11:18
All,
Speaking of GK of Spherical Trigonometry and Haversines etc, what were the papers for 2nd. Mates FG Exam., pre 1979
Principles of Navigation, Practical Navigation, Chartwork,was there Maths,, English anything else?
slick


I have posted a copy of MOT sylabus here slick. http://www.shipsnostalgia.com/gallery//showphoto.php?photo=256171

rgds
Neil

Glyn Howell
7th November 2010, 17:49
Joining in about sights and sextants, when I first made Third Mate after an apprenticeship with Anglo saxon I was fresh with theories about Long by Chron or Marc st Hilaire, at least, at the age of 75 I think that's the spelling, but came up against a Chief Officer with and Extra Masters Ticket by the name of Diston, from Newcastle. He used something called Air Tables, used I found out by Pilots, and he used to flash through the morning Star Sights. I proudly produced my Hewson Sextant with the sun as large as a sixpence, his first bit of advice was to "study, study and more study, get all your tickets, and then think about women". I believe he eventually made Examiner of Master and Mates at Newcastle. Strangely, since retirement I have not even thought about the sea even though I spent 47 years on it, but Air Tables? I never saw them again.

gra_am
7th November 2010, 23:25
Hi Glyn,
We, in BP, used air tables all the time. If I remember correctly they gave you the best 7 stars to work on any particular evening. Who didn't get a 'cocked hat'?
Educated 'guessing' we always knew where we were but never where we are.
I grew up on 'Burtons' but had to change to 'Norries' when I went to sea.
Nowadays they don't know what a log table is>

Graham

sidsal
8th November 2010, 15:49
Brings back memories of basic navigation - haversines, spherical trig,ampliudes, tide tables, Norries etc. Still have Nicholls Concise Guides Vols 1 &2.
First ship - Brocklebanls Maihar (1943)had only a magnetic compass in quadrantal form ( no 360 degrees nonsense !) Each change of course required a compass error calculation where possible. No running water, one salt water bath on board. No fridges - potato locker on the boat deck.
Tests prior to sailing involved only checking the telegraph worked, steam on the whistle to test - usually a demented sound of escaping steam and water, steering wheel both ways - and Bobs your uncle !!
Happy uncomplicated life.Taking cross bearings with quadrantal compass required correction for variation and deviation each time - kept the grey matter going.

John Cassels
8th November 2010, 19:45
Have said on a few posts over the years on SN that morning sun sights run up
to a noon latitide , then corrected back to ship's noon to give a noon position
that was holy grail was always fraught with danger.
No one can convince me that a sight taken from a bridge wing of a bulk carrier
rolling 30 deg. with a perhaps hazy horizon copuld be accurate.
All we did was cross two position lines with a run in between and hoped it would
be within 5 miles of where we were.

Air tables - American I think - were very good . used them all the time for
morning and evening star sights.

michaelF
8th November 2010, 21:09
But we always got there John , SShh , hope no gingerbeers read that.

mike

Billieboy
8th November 2010, 21:16
I used to be able to do the two empty Stella bottle trick, and then flog down a position using a slip-stick, the chief did the actual shoot and we timed with a Seiko. Used to drive the second mate Bonkers until someone told him one Sunday at drinkies!

chadburn
9th November 2010, 12:57
But we always got there John , SShh , hope no gingerbeers read that.

mike

Without hitting anything?(Jester)

Nick Balls
9th November 2010, 13:50
I think this is the answer to the thread question.
'C' as well as being the 'Answer for Azimuth' was also know as 'Longitude correction factor' That is according to Nories 'An error in longitude due to 1' of latitude. So C x D.Lat = Long (Correction ) for a sight correction in a 'days work' makes perfect sense.
I still have all my old sight books and this was indeed a daily routine in the 70's and early 80's on most ships.

michaelF
9th November 2010, 20:12
Thanks also Nick,
Anchorman (Neil ) sent me a copy from tables as i no longer have any , what ever happened to them all plus the books ?

Have added the scans as attachments just in case anybody else is interested!

mike

Anchorman
10th November 2010, 09:52
Joining in about sights and sextants, when I first made Third Mate after an apprenticeship with Anglo saxon I was fresh with theories about Long by Chron or Marc st Hilaire, at least, at the age of 75 I think that's the spelling, but came up against a Chief Officer with and Extra Masters Ticket by the name of Diston, from Newcastle. He used something called Air Tables, used I found out by Pilots, and he used to flash through the morning Star Sights. I proudly produced my Hewson Sextant with the sun as large as a sixpence, his first bit of advice was to "study, study and more study, get all your tickets, and then think about women". I believe he eventually made Examiner of Master and Mates at Newcastle. Strangely, since retirement I have not even thought about the sea even though I spent 47 years on it, but Air Tables? I never saw them again.

Just to remind you Glyn I have posted a link to tables below. In passing we had an examiner in Hull called "Charlie" Diston. Im sure many remember him. I certainly do!!

http://www.shipsnostalgia.com/gallery/showphoto.php/photo/224429/title/sight-reduction-tables/cat/500

Regards.
Neil

Glyn Howell
12th November 2010, 17:30
Neil, G'day.

Just viewing that attachment regarding tables I became quite faint!
As to Charlie Diston, well now, I never was quite as intimate as that even though I sailed with him as an apprentice as well, "Charlie" good grief, he was so awesome both in knowledge and with shoulders like barn doors I only went as far as "Mr". It was amusing that the Captain at the time was quite sniffy about a mate with an Extra Master, and I used to have a quiet grin in the dark after he had relieved the mate at at 06.30 and he muttered to me whilst I was on the wheel.

Thanks Glyn.