Sextant stuff: Letcher & HO 208

[dgadee]

I bought a used sextant about 10 years ago (Russion SNO-T - didn't realise how good it was and that it is basically a Freiberger) and have been collecting books on using it for that decade. At last I have decided to jump. Looking at the various approaches, John Letcher's 'Self Contained Celestial Navigation with HO 208' looks friendly enough. Anyone use that method?

I know everyone has their favourite method, but this one doesn't seem to be mentioned very often. Just wondered why.

 

[Skylark]

I enjoy Celestial Navigation and have a number of text books but not previously come across the John Letcher HO208 book.

Google doesn’t tell me much but there is one guy who seems to have written quite a comprehensive review on Amazon. It appears to have been written in the 1970s and has not been updated or amended.

From what I read, it does seem to be another variation of the Azimuth Intercept Method / Marc St Hilarie. I was pleased to read a review saying that the book does not encourage simply following a Template to reduce a sight. Agree with it or not, many people struggle with Astro and only make progress by using a template. People are different.

Most people learn to use AP3270 tables (as does the RYA Shorebased course). Some use the Reeds Astro Navigation Tables.

The objective of Celestial Navigation is to ensure that you are not close to bits that stick out and to help you get close towards your destination. If it works for you, why not.

Hope you enjoy it ?

 

[DMN]

I have a copy of Letcher’s book. It is very good because it doesn’t stop at Hc and Zn but goes into what John calls post grad topics, Specifically star identification from a Ho and Zn by working backwards (very useful under a cloudy sky so that constellations are obscured but individual stars may be seen), time approximations by lunar LOPs and great circle route calculations. Regarding the method of sight reduction, he uses the Dreisonstok tables and includes them in the book. These tables are very compact. But, they are no different in theory from any method requiring an integer LHA, Lat and hence an assumed position different from your DR position.

Reduction methods that allow the use of the DR position will use the haversine formula or the versine formula. My preference is to use the Reeds Astro tables, incorporating the almanac data and sight reduction tables. The whole book is lightweight and slim. The sight reduction tables are even more compact than those of Driesonstok and, in my view, just as easy to use. To use hav or ver formula methods, you need log cos tables and ABC azimuth tables. Reeds include these tables. Yet all up, the tables occupy only 12 pages. By including log cos (and log sin) tables and azimuth tables, you can do great circle route calcs and coastal plane sailing calcs for course, distance, departure to/from longitude etc.

 

[Sandy]

I was recommended David Burch's Celestial Navigation: A complete home study course by a navigator who I greatly respect. It is simple to follow, but if you want all the fancy maths that is there too.

Avoid the YouTube channel like the plague as he rambles on and on and on a bit like my old professors.

OOps I've just spotted the date of the OP.

 

[benjenbav]

I was recommended David Burch's Celestial Navigation: A complete home study course by a navigator who I greatly respect. It is simple to follow, but if you want all the fancy maths that is there too.

Avoid the YouTube channel like the plague as he rambles on and on and on a bit like my old professors.

OOps I've just spotted the date of the OP.

Thanks. I might just dig out my sextant and have yet another go at overcoming my inherent laziness.

 

[Uricanejack]

I used some awful text written by the Senior Lecture at Shields. which I wouldn’t recommend,it was very dull. it did the job but I believe did a better job of getting all the students who passed through and took the course into contributing to his retirement fund.
Mine through school had a nice rose smell and color after an incident with some Sandeman’s
Unfortunately I don’t know what I did with it.
So I found a copy on eBay to stick in my bookcase for nostalgia.

Today I recommend Bowditch. More correctly known as the American Practical Navigator. It’s a text book so still rather dry but it’s a good text book. Excellent reference.
Best part available to down load free by USG.

If you find you have any questions on Bowditch examples. I could probably make a pretty good stab at answering them.

Im sure Sir Tom will have a nice easily read little pamphlet available for the basic minimums. To get you started. I don’t think I’ve ever read it. Or have a copy. But his stile is easy reading a few do it better.

I didn’t spot the date, but if anyone is interested and had a question the offer still stands.

 

[Barnacle Bill]

Try Reeds Ocean Handbook which has a complete step-by-step guide using the concise sight reduction table in The Nautical Almanac (which you're going to need anyway).