Sextant

[PhilipH]

Anybody got/used an Astra IIIB sextant and if so, any views?

Decided need to learn and use astro nav.

 

[AndyKM]

the Astra IIIB is a good all rounder. It's easier to use than some of the more common split screen Russian and German equivalents, which can be tricky to get to grips with at first.

I was using an Astra recently, and found it well made, pretty accurate and easy to bring sun and stars down.

 

[AOWYN]

There is a steady stream of sextants on E-Bay. You are more likely to find a Frieberger on EBay UK and you will find it a perfectly adequate piece of equipment, really just a question of whether you want an East German or a Chinese unit. They are both good.

Enjoy learning Astro, it is very satisfying, even if some people deride it in today's world of GPS.

 

[poter]

I have also aquired a sextant recently
what is the best way to learn??? books; night school?

Also which book would you guys recommend for a complete novice?


poter

 

[Rowana]

[ QUOTE ]


Also which book would you guys recommend for a complete novice?




[/ QUOTE ]


I bought both "Celestial Navigation for Yachtsmen" by Mary Blewitt & "Celestial Navigation" by Tom Cunliffe.

I prefered the style of Tom's book, but others swear by Mary's.
Just depends on which style suits you, as both are good - and cost less than a tenner each

Have fun ! !

 

[alex_rogers]

I've used one with the full mirror and found it very easy for both star and sun sights. The illuminated scale is quite useful for star sights, although given an option, I'd give this up since the handle that contains the batteries and switch for the lamp is a bit 'plasticy' and undermines the quality of the rest of the sextant. The main body is very well made and it is easy to maintain and adjust.

You can pay a lot more for a sextant but this one does the job very well and is more than accurate enough - my average fix accuracy from a small yacht was three miles on a transatlantic. As a back-up for GPS it is ideal and is much more accurate than a plastic one.

 

[wooslehunter]

Got Tom's book & it worked for me.

Don't go and spend loads on sight reduction tables. You can download a complete set from here.

Software almanacs can be found on the web as well.

This is how I learned: - first learn how to do the sight reduction. Now learn to take a sight & practice. This way you can get a good fix assuming that the altitudes are right. Since you already know how to reduce a sight, any errors you get are due to the sight and not the reduction process.

For sight reduction practice, I found that a software star atlas is great. You can always reduce your own sights but they will have a certain error. The software will give you the exact altitudes of the bodies from anywhere on the earth at any time. hence you can practice the sight reduction and should get a really good fix. If not then you're doing something wrong. You can also simulate southern hemisphere etc etc.

One thing to remember though is that software star atlasses are designed to drive a telescope. Telescopes are referenced to the horizontal. Hence, altitudes will be not have to be corrected for dip but will have to corrected for refraction.

You can get loads of software for this these days but I have to say there's a sense of achievement in being able to get a good fix with just a sextant and some paper.

 

[PhilipH]

Thanks for responses - Looks like the Astra IIIB then.

I think I'll go for paper tables too - think I'm getting paranoid about electrical failures.