Aboard their two vessels, both named Yankee, Irving and Electa Johnson, circumnavigated seven times without drama or accident. During the course of those trips they had many young people aboard who learned to sail while having the adventure of their lives. That might seem old hat now, but in the 1930’s the Johnson’s pioneered an original program that has been the template for the many sail training programs at work today.
Irving Johnson was a heroic figure. Born on a farm in Hadley, Mass., in 1905, he graduated from the prestigious Hopkins Academy and then dropped out to master the craft of sailing and ship handling. One of his early passages, and one that he filmed with a hand-held 16 mm camera, was a passage aboard the German four-masted barque Peking, bound from Hamburg, to Chile via Cape Horn. That film, called Around Cape Horn, is one of the few filmed chronicles of sailing aboard a Cape Horner during the last days of those great sailing ships.
Johnson was sailing aboard the German pilot schooner Wander Bird, in 1931 when he met Electa. Later they married and decided upon their life’s work of sail training.
There were three Yankees. The first one prior to World War II was a heavily built North Sea pilot boat originally named Loodschooner 4. The ship was 92 feet overall, 76 feet on the water, with a 21-foot beam and drew 11 feet. They sailed this first Yankee from England to their home port in Gloucester, Mass., and began preparing for the 18-month circumnavigation. Before World War II they did two more circumnavigations.
The Johnson’s wrote copiously of their travels, including many articles for National Geographic magazine. One of their memorable discoveries was of the anchor of Bounty, found at Pitcairn Island. They sailed their last Yankee, a Sparkman & Stephens design, through the canals of Europe. Irving Johnson passed away in 1991, and Electa in 2004.
Johnson was an excellent navigator and in our problem Yankee is approaching Pitcairn Island on April 25 (we’ll use the 2008 Nautical Almanac, of course). Being very conservative he takes a morning star sight in order to get a fix. The DR of Yankee is 24° 55’ N by 129° 42’ W. His height of eye from the deck of Yankee is 15 feet. There is no index correction and no chronometer correction. We will solve this using Vol. 1 of H.O. 249, which is the Sight Reduction Table for Selected Stars. By using this table we eliminate some steps in the star reduction process. The two stars that Johnson shoots are Alpharatz and Arcturus. He shoots Alpharatz at 13:26:52 GMT and gets an Hs of 23° 27.8’. At 13:28:15 he shoots Arcturus and gets an Hs of 23° 38.8’.
A. What is the Ho of Alpharatz?
B. What is the Ho of Arcturus?
C. Using Vol. 1 of H.O. 249, find the intercept for both stars.
B. What is the Ho of Arcturus?
C. Using Vol. 1 of H.O. 249, find the intercept for both stars.
EXTENDED ANSWER:
David Berson
Even though Irving Johnson was a superior celestial navigator, I’m certain he would have appreciated the ease of usage of HO249 Vol. 1 for selected stars. Of course, at the time of his circumnavigations, this reduction table had not yet been compiled, so when Capt. Johnson did his star sights he did them the traditional manner; that is he used the SHA of the star combined with the GHA of Aires. Vol. 1 does away with a lot of the number crunching associated with star sights and makes it relatively simple to get a fix from two or more stars. I will not go into a discussion here about the advantages and disadvantages of Vol. 1 for selected stars. I will save that discussion for the next Ocean Navigator newsletter.
We are aboard Yankee on April 25, 2008. The DR is 24° 55’ N by 129° 42’ W. Height of eye is 15 feet. There is no index correction, nor any chronometer correction. Approaching Pitcairn Island, Johnson takes two evening twilight shots of Alpharatz and Arcturus. The Hs of Alpharatz is 23° 27.8’ and the time is 13:26:52 GMT. At 13:28:15 GMT he shoots Arcturus and gets an Hs of 23° 38.8’.
We are looking for the HO of both stars; For Alpharatz we have the following:
Hs 23° 27.8’
Dip -3.8’
Ha 23° 24.0’
Alt. Corr. -2.2’
Ho 23° 21.8’
Dip -3.8’
Ha 23° 24.0’
Alt. Corr. -2.2’
Ho 23° 21.8’
For Arcturus we have the following:
Hs 23° 38.8’
Dip -3.8’
Ha 23° 35.0’
Alt. Corr. -2.2’
Ho 23° 32.8’
Dip -3.8’
Ha 23° 35.0’
Alt. Corr. -2.2’
Ho 23° 32.8’
Next we have to go to H.O. 249 Vol. 1. The entering arguments in this volume are Latitude (whole number of degrees) LHA Aires. The first thing to do then is to calculate the LHA Aires of the two stars. We do this by using the usual procedure we are accustomed to for finding local hour angle of any celestial object. Here is what we do:
In the NA for April 25 under column for GHA Aires we find that at 13 hours GMT the GHA Aires is 48° 54.9’. To that we add the correction for 26 min., 52 sec.
GHA Aires 13 hrs 48° 54.9’
Inc. and corr. +6° 44.1’
GHA Aires 55° 39.0’
+360°
GHA 415° 39.0’
Ass. Long. -129° 39.0’
LHA Aires 286°
Inc. and corr. +6° 44.1’
GHA Aires 55° 39.0’
+360°
GHA 415° 39.0’
Ass. Long. -129° 39.0’
LHA Aires 286°
You will notice that I had to add a complete circle (360°) to the GHA Aires in order to get a large enough number so that I could subtract my assumed longitude. This is standard procedure and does not influence the result in any way.
We follow the same procedure for Arcturus:
GHA Aires 13 hrs. 48° 54.9’
Inc. and corr. +7° 04.9’
GHA Aires 55° 59.8’
+ 360°
GHA 415° 59.8’
Ass. Long. -129° 59.8’
LHA Aires 286°
Inc. and corr. +7° 04.9’
GHA Aires 55° 59.8’
+ 360°
GHA 415° 59.8’
Ass. Long. -129° 59.8’
LHA Aires 286°
Now we enter Vol. 1 on the page of 25° N Latitude (assumed latitude) and go to column LHA Aires and find LHA Aires 286°. You will see the Hc of Alpharatz at 23° 16’ and the Zn 067°. We then do the following to find the Intercept:
Ho 23° 21.8’
Hc -23° 16.0’
Hc -23° 16.0’
Intercept 5.8nm Toward
For Arcturus it is the following. In this case the Hc is 23° 45’ and the Zn is 281°
Hc 23° 41’
Ho -23° 32.8’
Intercept 8.2 nm Away
Ho -23° 32.8’
Intercept 8.2 nm Away
