This is for all of you old Salts out there. Sex-

[caguy]

tants is the subject. Had you for a second there! I just bought one and would like to try out this weekend and have a couple of questions. Is the Nautical Almanac good year after year or do you have to buy a new one each year? I've noticed that some are titled 200X and others have a specific year.The one that I am expecting in the mail soon was advertised as calibrated, does that mean that it will be accurarate out of the box or will I need to still adjust for error?How do you hold it still while out on the water?Do you need charts or can you get your location just from the tables?I have my watch set to within 1 second based on atomic time. I understand that if you are off by 4 seconds you will be off by 1 nautical mile. That to me seems pretty accurate. What is the closest you have been able to get to a GPS reading?I'm sure I'll have a dozen more questions when I open the box.

 

[tcbro]

I hate to tell you

but the sextant you bought is worthless. It was made as a nautical decoration not for navigation. Trust me, I have one exactly like it. There is no way you will get an accurate reading, not even close. To answer some of your questions;Yes, you need a new almanac each year. My guess is that some are marked 200X so they don't have to update their ad each year.Yes, you need to calibrate each time you take it out of the box. Temperature changes make this necessary. This is especially true with plastic sextants like the ones made by Davis (probably your next sextant).Practice, practice, practice. That's how you learn to hold it still.Charts? depends on where you are. If you are coastal, yes, you will need charts. If you are in the middle of the Atlantic they won't be necessary.I suggest getting one of the Davis sextants as they are relatively inexpensive and of a good enough quality to hone your skills. Compare it to your brass sextant and You will immediately see where it is lacking. Real sextants have a vernier dial at the bottom to get the precision required for navigation. If you want to go further you'll need something like an Astra for around $500-$600. Check www.celestaire.com for sextants and books.My brass sextant sits on a shelf in my office, that's all it's good for.Sorry,Toms/v Orion's Child

 

[Rich Stidger]

A couple of thoughts....

Apparently poster 'tcbro' knows of the sextant you bought and knows it is not very accurate.The Davis plastic sextant (Mk 15) is about $125 and will read to +- 0.2 minutes of altitude. That is OK for learning and general use, but it will not be fine enough to allow you to achieve high accuracy fixes.With a high quality temperature-compensated metal sextant you will be able to measure altitude to the nearest 0.1 second. Given an accurate watch or if you know what the watch error is (ie, how much it gains or loses per day), you can readily achieve fixes accurate to within 1 nm. I have personally achieved a two or three body fix within 0.6nm several times using a surplus Navy sextant. It's not rocket science, even a caveman could do it with some practice.....Sextant navigation is not for plotting your course into a harbor, but rather for open ocean navigation.Holding the sextant still while on a moving boat seems like an impossible task. However, what you need to understand is that the sextant is used to measure the angle between the horizon and a celestial body (star, moon, planet, sun). Both the horizon and the celestial body will appear to move at the same rate and direction from your boat, so the RELATIVE motion between them will be close to zero. Thus when you 'bring the body down to the horizon' it will appear as though both the horizon and the body are motionless.Good luck with your studies.

 

[Stu Jackson]

BOOKS

They have written quite a few about sextants. Mary Blewitt's is very good for beginners, Bruce Bauer's is also good, Chapman's and Dutton's also have sections on sextants. Do some reading.