Polish version

Navigational Astronomy

Practical Astronavigation

The admission and the theory, notions, amendments


Instead of the admission

I led big yachts through oceans several times. It irritated me, that through a few weeks officers (captains and sea steersmen) they will be bumping because they don't have (and must not have) of comprehending about the astronomical navigation, and I am supposed to chase the Sun, the Moon, planets, stars a day several times and to do calculations?!? Never again!

I got in writing and I did the textbook on a few sheets of paper astro in the version 'idiotproof'. After the fifteen-minute long lecture (zero theory, well she is needed exclusively for doing the doctorate) crew members drew the positional line, surprised it is so easy. Somebody took away from himself at the end of the voyage my 'textbook' to the keepsake, so for the new team (return voyage through the Atlantic) I wrote him one more time. Somebody also stole him in the end. I wrote around World in the S/Y ZAWISZA voyage 'work' once again, with this time of the typing (such a device existed at one time). I reflected it in the port office to Taiwan in 20 copies and I handed out to officers to the keepsake so that they must not take in secret. There were these 12 pages of the standard typescript and it contained algorithms of the conduct how to make the positional line from the Sun, the Moon, planets, stars, the North Star and how to calculate the initial angle of the road within 30 seconds after great circle sailing and distance great circle. It is at sea for people which know that GPS has the right to break down but in the middle of the ocean practically hard to call everything what is needed breakdown service.

My the 'textbook' had a life of its own for some time, xeroxed and copied with different techniques, almost as underground 'blotting paper'. The matter died away then, well universal (and accessible on account of the price) became GPS and more and more often navigational primer (crossing the course off on the map, the bearing to the lighthouse) was named 'history of the navigation'. I looked into the online discussion group in closing dates of the June (pl.rec.zeglarstwo) and a letter of the yachtsman returned my attention, which sextant he received, he is going for two months to the Adriatic and readily so that he practises for himself astro, but he is seeking the good, straight and intelligible textbook to the set.

I answered him that I had so and if is interested far I can send it to him with the e-mail, if only not to litter the mailing list. I obtained 5 next requests by half an hour late about 'textbook'. Sent the next day 'textbook' for entire six and I got a letter from 25 next willing. The day was proposed late above 50 persons... If such an interest exists, we decided my 'textbook' to publish as the addition to the magazine 'Rejs'. We are printing the textbook in such a version he, in which was written.

I need a favour, in order to persons which will use this small book to making the positional line from the free celestial object just for once, they wrote (with the e-mail, to the [email protected] editorial office address or my [email protected]) how did them.



1. If the theory is boring you, you can omit her, well position astro it is possible to find not having the slightest idea about the theory.
2. If you have so much perseverance in yourself that you want to know roughly, what it concerns - read far.




 Positional lines

What resemblance consists in - can see from the drawing.

1. The lighthouse is standing on the wharf, so the measurement is always the same in the same place (independently of the time).
2. Position CN there is a variable in the time, it is necessary so to have the exact time in the moment of the measurement.
3. You are as a rule very far (a few hundred miles) from the CN throw to the surface of the Earth (point CN'), so it won't be possible to draw the result on the map. It is necessary to do it differently, about what far.


B. NOTIONAL APPARATUS, that is what is what?


1. Dec. - declension (you will find in the 'Nautical Almanac').


 Declension of the Sun


2. GHA - Greenwich Hour Angle - (you will find in the 'Nautical Almanac')
3. LHA - Local Hour Angle




C: AMENDMENTS, it won't be sufficient to read only


Correct the tense deciphered on the chronometer according to principles:
Ch - reading of the chronometer
 +St - state of the chronometer (+ if is late, - if is in a hurry)
    Uo - time GMT
If you used the centre half, add the time to it from the centre half.


You measured the height CN = ho
Add the constant misconception of the sextant, taken from the certificate = cc
Add the mistake of the index measured up before or after the measurement = ci
You are receiving together ho+cc+ci=hs


The interactive sextant


Next chapter:
Practice - algorithm of acting in seven points



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