Astra 3 proffesional - SailNet Community
Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.

 1Likes
Reply
 
LinkBack Thread Tools
post #1 of 15 Old 4 Weeks Ago Thread Starter
Senior Member
 
jerryrlitton's Avatar
 
Join Date: Oct 2002
Location: Phuket, Thailand
Posts: 1,607
Thanks: 5
Thanked 18 Times in 18 Posts
Rep Power: 13
 
Astra 3 Professional

Help please, just bought an Astra 3 Professional with split mirrors. Aviation and maritime nav skills so I sort of know a bit about the concept. Almost failed geometry in school, definably not a math wiz. Can anyone point me in the general direction so I can learn how to use this thing? Thanks in advance.

"Let there be light!" said God, and there was light! "Let there be blood!" says man, and there's a sea!
Lord Byron, Don Juan


S/V Temptation
Islander 44
Very non-production
(Well, 10 were made so sort of non production)






To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Last edited by jerryrlitton; 4 Weeks Ago at 04:37 PM.
jerryrlitton is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
Advertisement
 
post #2 of 15 Old 4 Weeks Ago
Old as Dirt!
 
svHyLyte's Avatar
 
Join Date: Nov 2008
Location: Tampa Bay Area
Posts: 2,935
Thanks: 15
Thanked 129 Times in 122 Posts
Rep Power: 7
 
Re: Astra 3 proffesional

Quote:
Originally Posted by jerryrlitton View Post
Help please, just bought an Astra 3 Proffesional with split mirrors. Aviation and maritime nav skills so I sort of know a bit about the concept. Almost failed geometry in school, definably not a math wiz. Can anyone point me in the general direction so I can learn how to use this thing? Thanks in advance.
There really isn't much too it. You have the Sextant. You need good tables covering the latitudes where your sailing,and a good timepiece to record the time of your sights. A good simple book is
Celestial Navigation for the Yachtsman by Mary Blewitt. There are others of course. Click over to Celestaire Navigation for more information and resources.

"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
svHyLyte is offline  
Quote Quick Reply Share with Facebook
post #3 of 15 Old 4 Weeks Ago
Senior Member
 
Join Date: Nov 2012
Location: BC coast
Posts: 195
Thanks: 1
Thanked 10 Times in 10 Posts
Rep Power: 3
 
Re: Astra 3 proffesional

Yes.
Where to start what do you know? Or not know? What would you like to learn?

Do you know how to check a sextant for errors and adjust it?
Which would be a good place to start.
Your sextant may have come with instructions.
I can write out how but my computer skills lack the ability to draw a picture. a picture being worth a thousand words.

I can post how to check and adjust for error.

How to take an altitude?

How to correct altitude?

Then how to do the calculations if you like.
Uricanejack is offline  
Quote Quick Reply Share with Facebook
post #4 of 15 Old 4 Weeks Ago
Senior Member
 
Join Date: Dec 2014
Posts: 505
Thanks: 12
Thanked 36 Times in 36 Posts
Rep Power: 1
 
Re: Astra 3 proffesional

The process itself, alignment, correction, reduction is all learned by repetition. There's not much too it beyond a slavish devotion to accuracy and procedure. The toughest part for me is the actual sighting from a rolling boat thru cloudy tropical skies. I practice that, without doing anything with the numbers, as much as I can during cocktail hour.

I try to stay up on the book, pencil and paper sight reduction process in case the calculator dies someday. If the calculator works I just bang in the spherical triangles .... Geometry was my profession ....

"...there are two kinds of opinions, those based upon tradition ... and those having something in their favor." B. Russell
aloof is offline  
Quote Quick Reply Share with Facebook
post #5 of 15 Old 4 Weeks Ago
Senior Member
 
Join Date: Dec 2012
Location: new england
Posts: 2,320
Thanks: 54
Thanked 46 Times in 43 Posts
Rep Power: 3
 
Re: Astra 3 proffesional

It's fun. Personally found big bright objects are best to start with and simplest. Use your filters and start with figuring local noon. Then maybe lower limb of the moon when there's a full or nearly full moon. Then some category one stars. Start at anchor where you still have a horizon. I have a " good" sextant that was handed down through the generations in my wife's family, a "cheap" Chinese one and a plastic Davis. I play with the plastic one and I'm probably most accurate with that one. Have a ww2 airplane bubble one from my dad somewhere never figure that one out nor could I ever figure out how to use an artificial horizon to benefit me. Took a course in a HS planetarium from a old sailor. That was awesome.

s/v Hippocampus
Outbound 46
outbound is offline  
Quote Quick Reply Share with Facebook
post #6 of 15 Old 4 Weeks Ago
Reward for lost Kraken!
 
hellosailor's Avatar
 
Join Date: Apr 2006
Posts: 11,481
Thanks: 5
Thanked 132 Times in 129 Posts
Rep Power: 11
   
Re: Astra 3 proffesional

Celestaire are or were the importers, I'd see what they have first.

A book on sextant alignment and checking it over, to make sure it is in good working order. Sometimes there are alignment tools you might want.

Mary Blewitt' s little book, Mixter's Primer of Navigation, and Wm. Buckley's video on how to use the sextant are all classics.

Each approached things differently. Mixter walks you gently through the math and navigation all the way from ancient times to modern logic with spherical trigonometry--which frighteningly makes great sense for navigation!

Basically you need to know if the sextant is "bent" or aligned properly. How to zero it out before each use. And then, what to measure with it, along with how to take the exact time of the measurement. (I've used a cheap digital stopwatch, hacked to the real time, velcro'd onto the sextant so I could just "squeeze" to mark the exact time of a sight.)

Given the time, and the measurement, then you have the choices of using the tables and books and doing the math the traditional way, or punching the numbers into a calculator, a PC program, even an old Palm Pilot (cheap and reliable with good software available cheap) and when the numbers are crunched, you will still not know where you are.

You will, however, know that you are a certain distance from a certain point, i.e. someplace along a big curved line. Once you have done that a couple of times and can get a couple of lines to cross, THEN you know...you're someplace near there. How close you are, depends on how good everything else was.

Navigators, sextant or not, often refer to a "circle of position". You KNOW that you are somewhere in the circle. Sometimes the circle is a half mile wide, sometimes it is two hundred miles wide. With the best of sextants in the best of circumstances, a circle two miles across would be considered EXCELLENT.

And if you are at the shore, or near it? Twenty miles might be all you'll get, because of atmospheric distortions in coastal areas. So be patient, and try to get some used books or find a local helper. One of them will wind up talking in terms that makes sense to you. Might not be the first, or even the fourth.
hellosailor is offline  
Quote Quick Reply Share with Facebook
post #7 of 15 Old 4 Weeks Ago Thread Starter
Senior Member
 
jerryrlitton's Avatar
 
Join Date: Oct 2002
Location: Phuket, Thailand
Posts: 1,607
Thanks: 5
Thanked 18 Times in 18 Posts
Rep Power: 13
 
Re: Astra 3 proffesional

Thanks you all. I ordered Blewitt's and Mixter's book. Is it better to order sight reduction tables from an almanac or is there a better way?

"Let there be light!" said God, and there was light! "Let there be blood!" says man, and there's a sea!
Lord Byron, Don Juan


S/V Temptation
Islander 44
Very non-production
(Well, 10 were made so sort of non production)






To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
jerryrlitton is offline  
Quote Quick Reply Share with Facebook
post #8 of 15 Old 4 Weeks Ago
Senior Member
 
fryewe's Avatar
 
Join Date: Dec 2004
Posts: 1,621
Thanks: 31
Thanked 52 Times in 52 Posts
Rep Power: 11
 
Re: Astra 3 proffesional

Jerry,

You can download the Nautical Almanac and Pub HO229 at the following links.

http://msi.nga.mil/NGAPortal/MSI.por...2&pubCode=0013

The Nautical Almanac

You can either keep them on your hard drive, or put them on a finger drive or cut a DVD after downloading, or print the portions you think you may be using in the near future. Note that 229 is published in sections of 15 degrees latitude, so you can filter what you need from what you don't need. Nautical almanac data for stars (not for the Sun, Moon, planets) is the same from year to year.
jerryrlitton likes this.

The web makes everywhere the same place. - Fred Reed, from "Fred on Everything"
fryewe is offline  
Quote Quick Reply Share with Facebook
post #9 of 15 Old 4 Weeks Ago
Reward for lost Kraken!
 
hellosailor's Avatar
 
Join Date: Apr 2006
Posts: 11,481
Thanks: 5
Thanked 132 Times in 129 Posts
Rep Power: 11
   
Re: Astra 3 proffesional

Jerry-
There's also an author (and surveyor) named Hewitt Schlereth, if I haven't mangled his name. Published a series of books that were all tab-bound so they'd lay flat, covering a lot of navigation very nicely, including some PERMANENT ALMANAC volumes. They're "abridged" somewhat, not as precise as a big annual almanac, but the information repeats every nth year and they give you the ability to take one very durable book and have a functional compact replacement for the almanacs if you want it. I'd suggest getting that if you want "an almanac that can't crash", if you can find it.

But then for real reductions? Yeah, find an app for your smartphone, OR, pick up an old b&w Palm PDA that runs for six or eight weeks on two AAA cells, and John Manson's "Pilot Navigator" suite, if it is still out there. The Palm is cheap, the program is inexpensive, and it takes no time at all to do the reduction that way. I'd say you are way less likely to make mistakes, compared to running the numbers manually. If nothing else, using any software reduction program also gives you a fast CHECK on your calculations.

A friend of mine was puzzling over why we had moved 900 miles in one morning, and while they were puzzling...Right, I grabbed a sight, flipped the Palm, and found out very quickly that there was a second opinion. Before they could check the bum reduction.

There are dedicated nav computers, but between button cell batteries and collectors' prices...A dedicated Palm that lives in the sextant case ain't so crazy after all. It doesn't mind living in a ziplock bag, either.(G)
hellosailor is offline  
Quote Quick Reply Share with Facebook
post #10 of 15 Old 4 Weeks Ago
Old enough to know better
 
Join Date: Dec 2006
Location: Beacon, NY
Posts: 3,091
Thanks: 19
Thanked 128 Times in 124 Posts
Rep Power: 9
 
Re: Astra 3 proffesional

W. Buckley's video is on Amazon Prime I think. but his voice is so annoying.
miatapaul is offline  
Quote Quick Reply Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Sextants: Tamaya vs. Astra Pau Hana Daz General Discussion (sailing related) 7 01-23-2012 06:46 PM
Sextant - Astra III? clementck Gear & Maintenance 2 01-28-2009 08:45 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome