Old no-plotting method for finding Lat and long.

[Rumata]

Greetings,  gentlemen,

I'm pretty  sure that many of you are familiar with  the  method,  old one, which  I recently  discovered for myself.
I refer to C.A. ("Cloudy Weather" Johnson's "Double Chronometer  Method"). I found the copy of old book  and read and tried to use this method. At first,  it looks a little bit archaic, but  as soon as you pay a little bit attention  to quite straight forward rules everything became cushty (  East London's slang for "cool."). The method doesn't require noon sight and was developed for usage at cloudy weather when sun wasn't really available.  I don't want to overload you with details, but the main  principle is:  you take two observations supposedly a couple hours apart. It may be DR and after some run- new position (  lat.  and long)  Using a few corrections the lat and long are adjusted and you got your position.  The key correction table is Table II, which is originally came from Capt.  Norie ' Tables.  Also  Pub.260 concerning Sun azimuth is used.

I'm not saying it is a magic bullet, but I found it interesting especialy considering the fact the British Navy extensively  used it and the book had 34 reprints. before 1918.  This method is also described in  Captain  Lecky's great book "Wrinkles in  Navigation."

Anyway,  just wanted to  share it with  you.

Thanks.

BTW, below you can see the basic rules to do it

1. Let two chronometer observations be taken at an interval of about 1.5-2 hours.  Let the first be worked out with the Lat. DR at the time of observation:
2. Let the Lat Dr and Long. thus obtained be corrected for the nrun of the ship in the interval  between the observations, and let the second observation be worked with this corrected latitude.  Name these Longs. (1)  and (2)
3. The bearing of the sun at each observation is to be taken from an Azimuth TAble.
4. Enter Table II (  in  Johnson's book) with the Lat and bearings, and take from it two numbers (a) and (b) of which take the difference. or sum, according as the bearings are in the same or adjacent quarters of the compass. The difference of Longs divided by this difference or sum of (a) and (b) gives the correction for the second lat.  And (a) and (b) multiplied by the correctness for latitude give the corrections for the two  longs.  Both Longs. should agree.  zif not- it shows the corrections have been wrongly applied.  A good safeguard against error., peculiar to this method only.

There are some additional  nuances which  I did not include in this basic rules.  Just for general  idea.  :>:>

[BigBill]

Interesting

[Rumata]

Interesting

Thank you. I  ordered and already got  Pub. 260. Will try this method a few times when have more time handy. If so far  we can  use Pub. 229 and 249, plus NA, so I don't see too  much hassle in using another set  of musty-smelling  books.  Just for a change. ;> ;>

[BigBill]

Have you had an opportunity to try this yet? How did it go?

[Rumata]

Have you had an opportunity to try this yet? How did it go?

Not  yet, hopefully  soon.   Will write about  my tryout

[Rumata]

Have you had an opportunity to try this yet? How did it go?

Sorry for a very  long delay.  Unfortunately the  world events (  war  in Europe ) to some extent not too abstract to me.  Therefore, my mind is occupied for now  by different  subjects.  Hopefully I'll be able eventually to return  to  one of my favorite subjects-  celnav.  Thanks for understanding.

[amnvol1938]

Greetings,  gentlemen,

I'm pretty  sure that many of you are familiar with  the  method,  old one, which  I recently  discovered for myself.
I refer to C.A. ("Cloudy Weather" Johnson's "Double Chronometer  Method"). I found the copy of old book  and read and tried to use this method.

 I came across this thread yesterday while browsing and joined the forum. A few years ago I worked a sight by Johnson's method. I was proud that I was the only person alive who had used this method. But I was wrong! It seems that there is a small group of strange people who enjoy using old navigational tables.

I have the 1905 edition of On Finding the Lat and Long in Cloudy Weather etc.

I believe that Johnson's method is a modified Sumner method. Modified in the sense that the lat & long are determined by calculation rather then  by plotting. In Johnson's era the ony  practicable way of doing the calculations was by tables. Today with a calculator the calculations are easy.

You mention pub 260 for azimuth. In my opinion the A B C tables are the easiest and quickest way of finding azimuth. I use the tables from Norie but thay are also in  Burton and Blackburne. I cannot find them in Inman. The get a mention in Bowditch 1958 but the actual tables are not included.

For what it is worth I am an armchair navigator. I have never navigated when my life depended on it. From my username you my be able to guess another of my navigational interests.

[Rumata]

Greetings.

I agree that ABC tables are easier, but Pub.260 is used so I wanted to suffer the same way as the fellas who are using it. Just kidding. SAintHillaire method is pretty much plotting, not calculations. So some 19 century methods included quite a lot of plotting. I found Dutton 1943, eighth edition, gives a lot of dated solutions but from the knowledge point of view- they are interesting. Anyway, I am preparing to try Johnson's method. It is quite logical.

Thanks for your response.

And by the way, there is nothing wrong in being armchair expert. Famous Professor Vise discovered the island in the Arctic ocean without leaving his office.