celestial navigation software

B

bobhunt

Active Member
Joined
17 Mar 2007
Messages
50
Visit site
I've managed to get hold of a sextant for my bay of biscay crossing in july, and hope to try my hand at a few sun sights. But I'm lothed to buy an almanac and sight reduction tables for the one trip.
What i would realy like to find is some software that would allow me to do the number crunching myself,( ie digital copys of the books,) But also if I'm getting bogged down, would let me put in time and height of sight and come up with a position. (ie cheat) Does anyone know of such a thing? Oh and if it was cheap or free that would be good too.
thanks for looking bob
 
Celestial navigation is the main way to navigate following a power failure in mid ocean. That means that your laptop would not work.

When using celestial nav there are basically three elements to finding your position.

operating the sextant
carrying out the calculations
plotting the position.


practising two of the three does have some relevance, but it would be better to do all three.
 
These days the sextant is only for when all power fails and/or all the electronics are waterlogged and dead (and it has happened to me twice over the years). Buy a book of tables, download the almanac pages, and use a pencil and a waterproof casio watch (which does seem to survive when all the other stuff doesn't). Even without the watch you can get latitude, which is a great deal better than not knowing anything.
 
Look here.

You can use it to print off the pages if you want. But it is also useful for exactly what you are asking for - playing around to get your head around it before buying all the almanacs and tables. Nothing wrong with that.
 
Oh thank you people for taking the time to answer my questions. I've not had time to look at the recomended sites, but I feel I must answer those that have pointed out that what I'm asking is so wrong, I wholey agree and that is why I'm trying to educate myself, I love paper charts and look to gps as a back up. This is my first boat and Iv'e asked a few questions on this site and answered one, I'm leaving Tuesday when I get back I may have more questions but who knows I may have some answers, ok I know I'll just have more questions.
thanks Bob
 
pm me your email address, and I will send you some forms which will make filling in the calculations a relatively simple affair.
 
Agree about tables; they are expensive, limited in what you can use them for, and take up lots of space. There are plenty of sight reduction programs around for you to run on your PC. Others that are suitable for a PDA. Check out the Celestaire website and take your pick. I have used the Navy's NAVPAC Programmed for some years and it suits me well. The ability to select the observable stars in advance is especially useful. Your next option is to use the sight reduction table in the back of the Nautical Almanac (which you will need anyway) More complicated than the bookshelf-busting NP401 series but does the job. Finally, why not go for the simple maths calculator solution? Something like a Casio fx-85 costs about £7 and if you have any problems using it most 12 year olds can quickly put you on the right path. Buy 2 or 3 for the price of a set of tables in case one goes wrong. By using the basic trig formulae for resolving spherical triangles you can reduce any sight. Furthermore because you can use your EP rather than several "chosen positions", it is easier to plot (and understand). My routine at evening stars is to take as many observations as possible, reduce them on Navpac to bowl out the howlers, then select 3 or 4 to reduce by calculator or tables. If you have difficulties in obtaining the trig equations (sine & cosine formulae) PM me and I can send a crib sheet
 
Yes Malabar, the calculator solution sounds very interesting, if you could let me have a crib sheet, I'll borrow my sisters 12 year old. PM sent
 
If you let google do the hunting there are a few free programmes out there.

I must admit it is years since I actually used a sextant to take a sight, but I would suggest in the first instance your plan of using a software based system to get the practice in is a good idea, working the sight out is easy either with software ore tables, getting the angle right is the tricky bit and that needs practice. The sun and moon are not too bad, relatively easy to find and with the exception of Mer Alt not to pressing for time where as morning or evening stars is a very short opportunity especially if the aim is to take 6 in the hope of getting 3 half decent sights
 
You must log in or register to reply here.

Share this page

Top