Celestial Observations

R.Philip Griffin
20th January 2007, 23:49
Basic rules of navigation:- 1] One observation produces one position line and 2] two or more position lines are required for a position. I recall, when deep sea, the arguements between the followers of the Marc St Hilaire Intercept Method or the Marks and Spencer Contrcept Method as refered to by the followers of the Longitude by Chronometer Method. There were sometimes quite heated arguements as to which was best. I guess it all depended on your original tutor, which one you used. When working out stars as 4th Mate I found the former method easier to use.
Nowadays I believe the sextant gathers dust in a chartroom cupboard, and reliance is placed on the Satelite Navigation system; although I did read a letter in the Nautical Magazine about a 50000 tonner on a voyage from a Black Sea Port to Trinidad, via Gran Canaria [where they bunkered], and BOTH sat Navs died after leaving GC and the sextant had to come out. He was quite surprised that they made their landfall within a mile of calculated. It would seem the old sextant does still work quite efficiently, but is it used very much these days?

Naviguesser
21st January 2007, 00:12
Basic rules of navigation:- 1] One observation produces one position line and 2] two or more position lines are required for a position. I recall, when deep sea, the arguements between the followers of the Marc St Hilaire Intercept Method or the Marks and Spencer Contrcept Method as refered to by the followers of the Longitude by Chronometer Method. There were sometimes quite heated arguements as to which was best. I guess it all depended on your original tutor, which one you used. When working out stars as 4th Mate I found the former method easier to use.
Nowadays I believe the sextant gathers dust in a chartroom cupboard, and reliance is placed on the Satelite Navigation system; although I did read a letter in the Nautical Magazine about a 50000 tonner on a voyage from a Black Sea Port to Trinidad, via Gran Canaria [where they bunkered], and BOTH sat Navs died after leaving GC and the sextant had to come out. He was quite surprised that they made their landfall within a mile of calculated. It would seem the old sextant does still work quite efficiently, but is it used very much these days?

I think the cadets are the only ones who use it (Jester) Do you have examples of each method you mentioned? I want to see which one, if either, I use.

R.Philip Griffin
21st January 2007, 00:35
With the intercept method the lat & long of the DR are used, and the interecpt measured either toward or from that DR along the body's bearing. With Long by Chron the position line only passes through the Longitude of the DR across the bearing of the body. I hope that is fairly clear, it being 35-40 years since I used a sextant in anger, or rather worked out a sight.

Stephen J. Card
21st January 2007, 01:03
With the intercept method the lat & long of the DR are used, and the interecpt measured either toward or from that DR along the body's bearing. With Long by Chron the position line only passes through the Longitude of the DR across the bearing of the body. I hope that is fairly clear, it being 35-40 years since I used a sextant in anger, or rather worked out a sight.



Long by Chron for sun sights ( providing the sun is not close too the meridian) and Mark St. Hillarious for stars.

Stephen

Naviguesser
21st January 2007, 01:15
With the intercept method the lat & long of the DR are used, and the interecpt measured either toward or from that DR along the body's bearing. With Long by Chron the position line only passes through the Longitude of the DR across the bearing of the body. I hope that is fairly clear, it being 35-40 years since I used a sextant in anger, or rather worked out a sight.

Haha okay I use the intercept method (Thumb)

David Davies
21st January 2007, 09:11
Out of interest whilst on this subject has anyone experimented with the Lunar Distance methods and what was the result? Some time ago I read the Dava Sobel book Longitude which resurected memories of passing time on anchor watch by calculating GMT by the lunar - stellar method in the Admiralty Navigation Manual which gave fair results. After much research I bought the 2001 Nautical Almanac £28 (they used to be 8 shillings) and calculated some selective lunar distance tables. The pre 1952 Right Ascension Almanac would have been better than the GHA one, but armed with my tables and my old "ham Bone" I made my observations which gave GMTs within 28 secs either way which I found satisfactory.

Nova Scotian
21st January 2007, 14:25
As a pre-sea cadet, at KE VII Nautical College in 1964, the M.St. H method was instructed. On joining my first ship I found that most of the mates were still into Long by Chron. Later on in my career I purchased a set of quick method tables and took them to sea with me on my first trip as 2/0. The Old Man threatened to drop my tables and plotting sheets over the side if he ever saw them in the chartroom. This is the same guy who who thought I was being funny when I mentioned I had got Mer Alt of Venus during the morning 8 -12. It seemed to me that every new innovation in sight-taking was always frowned upon by those that had been there before.

Quick method, Long by Chron, or M.St. H.....it all amounts to the same position line on the same part of the ocean. I always thought we Mates liked to make the business of sights seem far more involved than it actually was.

I now find myself preparing to instruct a course to mariners who will be challenging a Transport Canada examination in Astro-Nav. So, it's still around and will be for some time to come.

I would like to show my class an example of a typical Sight Book page(s) with morning sight run to a Mer Alt and calculations for days average and total average etc... Or an actual star sight calculation. Can anyone help me out with this? Unfortunately I have discarded my own books over the years.

Cheers, and what time is noon!

Tony Crompton
21st January 2007, 16:34
[QUOTE=Nova Scotian;102533] This is the same guy who who thought I was being funny when I mentioned I had got Mer Alt of Venus during the morning 8 -12. QUOTE]

Hi,

Used to think it was one of my "Party Tricks" finding Venus during the morning. Working out what the altitude should be, setting it on my sextant and pointing it on the calculated bearing over the gyro repeater and there it was in the sextant mirror. By being a real smart ar** and holding the sextant upside down you could spot it with the naked eye!!
-----------------
Tony C

slick
21st January 2007, 16:54
All,
An interesting thread especially the mention of Quick Method Tables, I purchased a set of Myerscough and Hamilton myself, "Rapid Navigation Tables for Mariners" much to the annoyance of various Masters I sailed with, however it made sight taking a pleasure.
In an earlier phase of my career I was with a Captain that made the two mates taking the noon sight hand over their completed calculations (which had been worked out seperately) to him, he would then go into the Chartroom and plot the said fix on the chart and that was it!!
Ah!, halcyon days.
Yours aye,
Slick

K urgess
21st January 2007, 17:01
Oh the mysteries of navigation.(EEK)

I was always completely baffled.
Lots of people wondered at the white man's magic of the radio cave but the mysteries of the chart table and Norrie's I always thought a lot more worthy of wonderment. (?HUH)

As for the world of boiler, turbine, scavenge pump and seperator. Well I still stand in awe. Minions of Danté.(Gleam)

Keith Adams
21st January 2007, 19:13
When one thinks about it, using computer/calulators and the like in figuring the ships position is just as alien to the modern day 'Old man' (in his 60s) as using short/quick method tables were during the 1950s...being quite comfortable and confident with the older method and not undertanding the new was really a big problem for the person ultimately in charge. My most recent trip as an AB on the wheel, I was dismayed that no visual bearings or visual distance off angles were taken, infact Azimuth Rings were not even
placed on the bearing compasses the entire round trip! Everything was done
on the Radar/Navigator Plotter with positions transferred to an actual chart;
I was most uncomfortable with it...an example of how an old timer feels
about total reliance on new/quick methods... not that the old methods were that much slower. At least I used to keep fit going up and down the vertical
ladder to the Monkey Island or out to bridge wing. Snowy
were taken

paul0510
22nd January 2007, 08:27
Hi Nova Scotian,
still got my sight books although you would maybe have a hard time decoding 'em as all the detail, column headings or whatever (LHA, Decl, Hav etc) I had in my head. And if I'm honest about it, I would probably have the same problem myself today!! But, if you like, I'll scan a couple of pages and put 'em in the gallery.

Brian Twyman
22nd January 2007, 09:23
As a young App in the RFA I learned both M.St H and Long by Chron methods, but invariably used the former. Calculations were done in a blank book. Passed Second Mates with questions on both methods !.

On joining RNZN I found Grey Funnel Lines use 'Altitude & Azimuth Tables (HD 486 ?) and a sightbook with all the columns & lines labelled plus hints whether to + or -. It is M.St H with the intercepts and bearings obtained from the Tables rather than calculated by haversine formula.

First overseas trip I had to sit my RNZN Ocean Nav. Certificate !. Oh dear, no Tables onboard for Latitudes 20 -30 !! (EEK) "Not a problem" says I and did the trip using haversine method . Sightbook sent to Fleet Navigator who responded ".. seems to know what he was doing ."
It was awarded (A)

Brian

paul0510
23rd January 2007, 19:40
...as promised a page out of my sight book dated July '71, at which time I was aboard the British Beacon as 2M on the trip back from ZSC (Capetown) to Ras al Khaimah. Nova Scotian, I actually found exactly two pages where the details have a name!! I can only surmise, that I was playing host to a Nav App who must have been completely baffled at my willy-nilly notations!
Together with this page in the 'Life Onboard' gallery I have included a typewritten 'crib' note from the C/E (Sammy Fewlass?) that enabled me, on this somewhat engine-troubled vessel, to calculate a feasible ETA !! Thanks, Sam!

Nova Scotian
23rd January 2007, 23:11
...as promised a page out of my sight book dated July '71, at which time I was aboard the British Beacon as 2M on the trip back from ZSC (Capetown) to Ras al Khaimah. Nova Scotian, I actually found exactly two pages where the details have a name!! I can only surmise, that I was playing host to a Nav App who must have been completely baffled at my willy-nilly notations!
Together with this page in the 'Life Onboard' gallery I have included a typewritten 'crib' note from the C/E (Sammy Fewlass?) that enabled me, on this somewhat engine-troubled vessel, to calculate a feasible ETA !! Thanks, Sam!

Thanks Paul....a copy to show them how it was!

slick
24th January 2007, 08:41
All,
I too have a couple of my old sight books which I will post a copy of a page or two soon.
On a similar vein did you own your own sextant?, in the course of my career I owned two the first was a Hezzanith of 1946 vintage which I bought off a Captain Bulmer of Hains, the second was a "Freiburger" of East German origin bought in 1964 in HK they both travelled the world with me.
I finally sold the "Freiburger" to a budding Second Mate, I heard later that it ended up hanging up on a wall!!, as a decoration.
I think that says it all.
Yours aye,
Slick

R.Philip Griffin
24th January 2007, 13:15
All,
I too have a couple of my old sight books which I will post a copy of a page or two soon.
On a similar vein did you own your own sextant?, in the course of my career I owned two the first was a Hezzanith of 1946 vintage which I bought off a Captain Bulmer of Hains, the second was a "Freiburger" of East German origin bought in 1964 in HK they both travelled the world with me.
I finally sold the "Freiburger" to a budding Second Mate, I heard later that it ended up hanging up on a wall!!, as a decoration.
I think that says it all.
Yours aye,
Slick
Ahoy Slick. I paid £30 for my Sestral in 1955[a month's wages] and it travelled the world with me. I gave it to No.1 son [Class 1 Master] and it collects dust in his house not mine. Sat Nav has killed the art.

vic pitcher
24th January 2007, 14:19
Ahoy Slick. I paid £30 for my Sestral in 1955[a month's wages] and it travelled the world with me. I gave it to No.1 son [Class 1 Master] and it collects dust in his house not mine. Sat Nav has killed the art.

I bought my Kelvin Hughes "Mate" (1956 vintage) from the 2nd Mate of .the "Homer City" for £20.oo early in 1960 when I was just finishing my "time." We were in Emden and he had decided to treat himself to a "Plath," much to the disgust of his fiancee who was on board at the time. It was last used in anger 1983-86 and now graces the bulkhead of my conservatory. I still have all my old sight books, fascinating to look back and see where I was at Noon 40 odd years ago.

Chris Field
24th January 2007, 14:33
A couple of points worth considering:

A few years ago I was with Pacific Forum Line hurtling around Papua New Guinea etc- the coastlines as charted hardly ever matched the radar picture accurately, and the sat-navs appeared to put us in positions several miles from where we damned well knew we were. As a result, as Old Man, I urged the mates to concentrate on where we were in relation to the dangers rather than in relation to the centre of the earth. This was simply achieved by good old fashioned bearings/radar distances etc and leaving the sat-nav to twiddle its thumbs while we got on with the trip. Once deep-sea again they would check the accuracy of the satnav by Marc St Hilaire etc- sat nav was usually pretty close to the truth!

On the other hand, I'm sure that Cook in 1769 would have said "I want one-GIMME!" if they had been around then- he loved maodern technology.

David Davies
24th January 2007, 15:55
Interesting observation on New Guinea and certain Pacific Islands. The mention of Lt James Cook RN brings to mind the fact that the position of certain islands in that area may be in error as charted. Generally the latitude is accurate but the longitude can be in error as although chronometers came into use by the early navigators, Cook took the Harrison No3 with him, most longitudes were calculated by Lunar Distance which in my experience were not perfect. In my earlier thread, as an inexperienced observer of the lunar distance I got to 28 secs in GMT which equates to 7 minutes of longitude distance of course being relative to latitude. In my time 49 to 63 there were many examples of longitude error some of which I reported and eventually was reward by a PA in relevant Notice to Mariners.said to be 3' further East than charted

lakercapt
24th January 2007, 21:35
Out in the Pacific I used to take star sights on a regualar basis. Was specially requested to get a fix one morning as w were to make a landfall later in the day.
Got a good fix using 5 stars and later on that day did make a landfll. That showed my sights were out by several miles which I found disappointing and nver lived it down.
Some years later with satellites it was when major changes in positions on land masses were made I realised that it was me that was right all along. Course had we run aground you would have still ben aground whither right or wrong!!!!

Brian Twyman
25th January 2007, 01:12
Having spent some time on HMNZS Tui trying to find some of these vigias (reported dangers) I can confirm that extreme care must be taken in the South Pacific. Some you can find in the area, some you cannot. Having said that, we had no Sat.Nav. and positions were as obtained by me using celestial sights !. Likewise many of the coastlines do not match the chart.
The scarcity of shipping in the area and the greater scarcity of hydrographic reports submitted, means that they may never be surveyed. Mariners should return to the basic rule of reading the date of survey under the chart title and allowing for a large margin of error.
Great fun navigating though, especially on discovering a peak which was not charted !

Cheers
Brian

David Davies
25th January 2007, 07:07
lakercapt
Was the charted error in the longitude ? the latitude ? or both ?

jazz606
25th January 2007, 09:26
Long by Chron is easier to plot P/L straight through calculated Longitude and DR Lat. I to started using Air Tables where you used to flog the DR Lat to give a whole degree of LHA. This led to some big intercepts which made some masters v-nervous. Not as nervous as they got when you used a calculator though.

On some of the big RFAs we had a Senior 2/0 who was the Navigator and did not keep a watch. Consequently I as 3/O often only took a morning sight and the S2/0 and Junior(or ordinary...?) 2/O would do the noon position between them the latter using my morning observation. Anyway I was on the 8-12 this evening and the S2/O was still on the bridge fiddling with his star sights and muttering to himself as they didn't tie in with the DR from Noon by 10 or 20 miles (can't remember now). It transpired that he and the other guy had misapplied the intercept (away rather than to or vica versa). He got into a real lather about this and didn't heed my advice (knowlegeble 22 year old) to keep quiet and average out the difference to next day's am stars. We were in the middle of the Indian Ocean and it wouldn't have mattered. He confessed to the Old Man (senile old git) who got the Ch/off (ambitious little p***k) to conduct an enquiry (witch hunt). I thanked my lucky stars (no pun intended) that I wasn't too closely involved - they went through everbody's sight books and everything. The S2/Os confidence was so badly affected that he couldn't get anything right after that and was replaced at the next port. My own career in the RFA was less than glorious and included the most miserable year of my seagoing career to the extent that I refused to sign the new articles during a routine change - it's useful to know your rights sometimes and it was worth it to see the look on their faces. Anyway moved on to pastures green in some senses of the word after that.

lakercapt
25th January 2007, 15:17
The error was mainly in the long. so maybe their chronometer was out. The original surveyors) As it was a long time ago I only rember the ribbing I took for getting it wrong when I told everyone it was a good fix!

jazz606
25th January 2007, 16:09
If you had a good cross of the P/Ls and your timing was ok you'd have to be right.

I used to take two good stars (if possible) twice alternately and maybe one or two more as a standby. Then just work out the two twice alternately plotting them you got a very small rectangle or square. If it looked dodgy I worked out one of the spares. Sounds long winded but wasn't - using air tables.

Nova Scotian
25th January 2007, 18:21
When I was at sea, the most reliable method of fixing a position by sextant was by stars. This was usually the responsibility of the Mate who generally kept the 4 -8 watch.

During the day the responsibility of determing a position at noon was shared between the 3/M and the 2/M. They would both take a sight of the sun in the morning using a DR based on the Mate's morning star position. I often wondered why the 2/M had to drag himself up to the bridge, after only a few hours of sleep, to do this. The resultant postion line was then run up and crossed with a meridian altitude of the sun. The ceremony associated with the noon observation was almost comical. This position was then adjusted to identify a position for 1200 hrs. The 1200 position was used to determine day's run particulars and ETA's to the next AC or EOP. The Mate would then take it upon himself to find out where the vessel actually was again by taking evening stars.

As far as can recall it was as basic as that. Now and again I can remember crossing sun position lines with well defined depth contours or radio bearings of weather ships, and the odd meridian altitude of a planet during the day.

In 1972, while on the Atlantic Conveyor, we were fitted with an Omega Navigator and that was the beginning of the end for practical sextant navigation on the Atlantic.

Cheers.

Chris Field
25th January 2007, 19:08
Great stuff, you sextant men!
One of my proudest moments was as (uncertificated) 4th Mate on City of London I (1954) in the Red Sea.I showed the mate (Thos Robinson, a real gent ) where we were at 0530 through my star-sights, he told the Old Man, (Capt. Jeffers- another great guy) who promptly ordered the relevant course in to the pilot position off Jeddah. The pilot was later sighted dead ahead being propelled towards us in a canoe paddled by a 14-year old, several miles offshore. Beat that, Mr. GPS!

John_F
25th January 2007, 21:39
When I was at sea, the most reliable method of fixing a position by sextant was by stars. This was usually the responsibility of the Mate who generally kept the 4 -8 watch.

During the day the responsibility of determing a position at noon was shared between the 3/M and the 2/M. They would both take a sight of the sun in the morning using a DR based on the Mate's morning star position. I often wondered why the 2/M had to drag himself up to the bridge, after only a few hours of sleep, to do this. The resultant postion line was then run up and crossed with a meridian altitude of the sun. The ceremony associated with noon observation was almost comical. This position was then adjusted to identify a position for 1200 hrs. The 1200 position was used to determine day's run particulars and ETA's to the next AC or EOP. The Mate would then take it upon himself to find out where the vessel actually was again by taking evening stars.

As far as can recall it was as basic as that. Now and again I can remember crossing sun position lines with well defined depth contours or radio bearings of weather ships, and the odd meridian altitude of a planet during the day.

In 1972, while on the Atlantic Conveyor, we were fitted with an Omega Navigator and that was the beginning of the end for practical sextant navigation on the Atlantic.

Cheers.
Nova Scotian,
What you have described was exactly the daily procedure in BP as well, although the 2nd Mate usually didn't drag himself out of bed for the morning longitude sight - this was left to the 3/0. However, the noon position procedure was always a joint effort between 2/0 & 3/0 & sometimes the Old Man if he wanted to keep his hand in.
As a 3/0, I only had to do the star sights on a couple of occasions, when sunset fell during the 8-12. I took great satisfaction on both occasions when I was able to prove a very doubtful Old Man wrong. Grudgingly, when I paid off, he endorsed my Watch keeping certificate with "He is an able navigator."
Kind regards,
John F.

K urgess
25th January 2007, 22:11
I love it when you all talk dirty. (LOL)

This is as close as a sparkie wants to get to the "noon sight" process.

http://www.shipsnostalgia.com/gallery/showphoto.php/photo/35961/si/weirbank/what/allfields
or
http://www.shipsnostalgia.com/gallery/showphoto.php/photo/35962/si/weirbank/what/allfields

I have a further one that I haven't posted where the old man has noticed the camera and is giving me the sort of look reserved for something he scraped off his shoes.
I must've disturbed his chain of thought.[=P]

John_F
25th January 2007, 22:59
I love it when you all talk dirty. (LOL)

This is as close as a sparkie wants to get to the "noon sight" process.

http://www.shipsnostalgia.com/gallery/showphoto.php/photo/35961/si/weirbank/what/allfields
or
http://www.shipsnostalgia.com/gallery/showphoto.php/photo/35962/si/weirbank/what/allfields

I have a further one that I haven't posted where the old man has noticed the camera and is giving me the sort of look reserved for something he scraped off his shoes.
I must've disturbed his chain of thought.[=P]
Fubar,
A picture is worth a thousand words........these scenes must have been repeated daily on most vessels when deep sea, pre GPS. You can almost hear the Old Man saying "......& I reckon we'll have done 310 miles."
Kind regards,
John

jazz606
25th January 2007, 23:18
I was acting 3/m on the Cape Sable in 1964/5. I had been hurriedly and temporarily promoted when the 3/m got the sack. Since I hadn't got a sextant the Mate kindly let me use his. It was a hezzanith vernier becoming slightly out of fashion in those days when micrometer sextants were the in thing. The old man used to take the noon sight with us and then loiter on the bridge making sure there was no conferring while I and the 2/m finalized the noon position. He would then ask what we each had. If there was more than a minute difference we would have to check it all again for gross error.

I realize now that it was all good training and stood me in good stead for 2nd Mates orals and written.

R.Philip Griffin
26th January 2007, 00:59
I love it when you all talk dirty. (LOL)

This is as close as a sparkie wants to get to the "noon sight" process.

http://www.shipsnostalgia.com/gallery/showphoto.php/photo/35961/si/weirbank/what/allfields
or
http://www.shipsnostalgia.com/gallery/showphoto.php/photo/35962/si/weirbank/what/allfields

I have a further one that I haven't posted where the old man has noticed the camera and is giving me the sort of look reserved for something he scraped off his shoes.
I must've disturbed his chain of thought.[=P]
Marconi Sahib, After reading lots of your posts, I can't believe the Master would ever treat you as a shoe addition, with your sense of humour. Many thanks for the photos, as John said the same types at the same time [Noon Mer Pass]all over the planet, we did this thing. I sailed with a Capt.G.A.Smith "Ceramic" SS&A, he insisted C/O;2/O;3/O;4/O and the two Cadets all took morning sites and Noon, did the days run, ETA's etc., and no collusion,but only the 2/O went in the log book, and only the Captain knew what each officer had done. The biggest cock up was on passage between Cape Town and Fremantle on a composite GC passage, when we mustered for Noon and there was a bloody partial eclpise. Our good Captain was the only navigator who knew and were the bollockings handed out that day, and it was Christmas Day. I think we were between Amsterdam Is and St Paul Is, and there is usually a lot of 8/8s down there, so getting Noon was very chancey. Life on the Ocean Wave.

Brian Twyman
26th January 2007, 09:16
Once when I was App in the RFA we were with the RN Fleet and the task was set by the Admiral for all ships to report the noon position as calculated by officers under training.
Reports started pouring in from 1201, Captain gave me a quizzical look, and I informed him that Mer Alt was not until 1320 LT because the fleet had not changed the clocks to the new Time Zone. Much mutterings to Second Mate who nodded ! Reported noon position to Admiiral at 1325 and received his compliments ! Our ship won the competition ! ( No prizes though !) (Thumb)

Brian