Astro tables

[Neil]

For those who like to know the maths behind these sight reduction tables, here is the author's response to an enquiry I made some time ago:

"You will find a detailed explanation of the book at
http://gbennett.customer.netspace.net.au/ etc. (interesting links and downloads here)

However the mathematical basis of the tables is as follows:

LHA & SUM : J Log sinx/2
LAT & DEC : J/2 log cos x
L ~ D & RES : K(1-cosx)
where J = -26059.70314 and K = 99999.

All logarithms are to the base 10 and
all results are rounded off to the nearest integer.

The formulae using these functions is given in Bowditch,
The American Practical Navigator as follows,
hav theta = cos Lat cos Dec hav LHA
hav (zenith distance) = hav (Lat~ Dec) + hav theta

George Bennett."

The tables are thus a modified and compact form of the standard cosine-haversine formula, which is also the basis of AP 3270 and most inspection tables. For the user, no knowledge of logarithms or spherical trig is required, just simple addition.

I'll definitely look into this when I have more time - I have a fantasy of eventually doing it all on paper without tables - It's probably not worth the effort, but if you re-invent the wheel, you should then know how it works!

 

[Neil]

Thanks! unfortunately, it's password protected so cant be printed. I also noted there were no 'Increments' pages - are you supposed to interpolate from 'd' ? but what about the moon? Maybe I should read the book again.....

Just answering my own question here, for any other's benefit:

http://www.navsoft.com/downloads.html

 

[BelleSerene]

Cunliffe bases his workings on the full tables - as a beginner, will I be able to extract the correct data from these apparently condensed works?

Yes. Use the far, far simpler Reeds Astro-navigation Tables 2010 (Lt Cdr Harry J. Baker) - just under £15 from Amazon: http://www.amazon.co.uk/Reeds-Astro-navigation-Tables-Harry-Baker/dp/1408116413

I found it no problem to teach myself from St Cunliffe's little book (brilliantly communicated, as everything the man writes) and the Reeds tables. You do have to update the tables every year, so it's £15 per year. But the tables are barely thicker than Cunliffe's magazine-sized book, which makes the whole thing manageable.

 

[smartcom]

If you want the UKHO publications, try www.bookharbour.com, Kelvin Hughes' online shop. As the site can be a bit diffuicult to navigate, they'll also take orders over the phone.
Tim