Celestial Navigation: Nautical Almanac - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
 Not a Member? 

Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


Reply
 
LinkBack Thread Tools
  #1  
Old 03-28-2010
Junior Member
 
Join Date: Mar 2010
Location: San Francisco
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
SeppSF is on a distinguished road
Celestial Navigation: Nautical Almanac

Even in the days of GPS one should know to find your position by classic celestial navigation. Just in case my GPS fails. Finally, I had some time on my last vacation and got a great book for that: Starpath, Celestial Navigation from David Burch.

Then I got back home and access to my Sextant and my 2010 Nautical Almanac I wanted to see if I can find my position. But the Sight Reduction Table is different to the ones I have in my study material.

It doesn't show Hc, d and Z but A/H, B/P and Z1/Z2. I also miss the SAME and CONTRARY part.

Who has an idea what to do?
Reply With Quote Share with Facebook
  #2  
Old 03-28-2010
Senior Member
 
Join Date: Aug 2006
Location: Arlington, VA
Posts: 1,807
Thanks: 0
Thanked 4 Times in 4 Posts
Rep Power: 9
btrayfors will become famous soon enough btrayfors will become famous soon enough
AFAIK, the Nautical Almanac provides celestial positions for the sun, moon, planet, and navigational stars. It does not include sight reduction tables. For these, you need a set of tables such as HO 214, 229, 249, etc. These are available for free download, as is the 2010 Nautical Almanac.

For the Noon Sight (latitude by meridian transit) you only need the Almanac. Here are the three cases:

Sight reduction tables are not required for these computations.

Case #1: When latitude and declination are of the same name, but latitude is greater than declination, use the formula:

Lat = (90̊ - Ho) + dec

Example: The DR latitude of a yacht at time of LAN is 40̊ N. The declination of the sun for that date and time is 20̊ 15.0' N. Since latitude and declination are both North (same name), but latitude is greater than declination, the above formula is used. Assuming the corrected sextant altitude (Ho) to be 69̊ 45', the solution is as follows:

Lat = (90̊ - 69̊ 45.0') + 20̊ 15.0'
and thus, Lat = (20̊ 15.0') + 20̊ 15.0' = 40̊ 30.0 North

Case #2: When latitude and declination are of the same name, but latitude is less than declination, use the formula:

Lat = dec - (90̊ - Ho)

Example: Assume the observer is in latitude 10̊ South and declination is 18̊ South. Since latitude and declination are of same name, but latitude is less than declination, formula #2 applies.

Case #3: When latitude and declination are of opposite names, use the formula:

Lat = (90̊ - Ho) - dec

Example: Assume the observer is in latitude 13̊ South and declination is 4̊ North. Since latitude and declination are of opposite names, formula #3 should be used to obtain observer's latitude.

Bill

Last edited by btrayfors; 03-28-2010 at 08:50 PM.
Reply With Quote Share with Facebook
  #3  
Old 03-29-2010
QuickMick's Avatar
Senior Member
 
Join Date: Oct 2009
Location: California
Posts: 1,381
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 5
QuickMick is on a distinguished road
you might want to check out bruce bauer The Sextant Handbook,
its a great resource...

Amazon.com: The Sextant Handbook (9780070052192): Bruce Bauer: Books
__________________
How inappropriate to call this planet Earth when it is quite clearly Ocean ~ Arthur C. Clarke

Quinn McColly
Macgregor Venture
Reply With Quote Share with Facebook
  #4  
Old 03-30-2010
AdamLein's Avatar
Senior Member
 
Join Date: Nov 2007
Location: Coquitlam, BC
Posts: 1,866
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
AdamLein will become famous soon enough
Quote:
Originally Posted by SeppSF View Post
But the Sight Reduction Table is different to the ones I have in my study material.
I think the nautical almanac has a simplified ("emergency") sight reduction table. I also recently found

Erik's Nautical Web Pages

To be handy.

Quote:
It doesn't show Hc, d and Z but A/H, B/P and Z1/Z2.
Not sure what A/H etc. are. Maybe A/H is GHA? The Nautical Almanac tables I'm familiar with show GHA and Dec for each body, plus some extra corrections for the moon.

Quote:
I also miss the SAME and CONTRARY part.
Two coordinates have the "same name" if they are both east or both west for longitude and hour angle, or if they are both north and both south for latitude and declination.

Quote:
Who has an idea what to do?
My life doesn't depend on celestial navigation and I don't feel like paying for the book. I use "The Online Nautical Almanac"
__________________
s/v Essorant
1972 Catalina 27
Reply With Quote Share with Facebook
  #5  
Old 03-30-2010
sailingdog's Avatar
Telstar 28
 
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 9 Times in 9 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
While that's a great book on sextant maintenance and such, it does nothing for you when it comes to navigating with a sextant.
Quote:
Originally Posted by QuickMick View Post
you might want to check out bruce bauer The Sextant Handbook,
its a great resource...

Amazon.com: The Sextant Handbook (9780070052192): Bruce Bauer: Books
__________________
Sailingdog

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

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
.

Still—DON'T READ THAT POST AGAIN.
Reply With Quote Share with Facebook
  #6  
Old 04-03-2010
Junior Member
 
Join Date: Jan 2010
Posts: 14
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
timtwickham is on a distinguished road
You could have a look at software to give you the almanac and do the sight reduction calculations - see WinAstro Celestial Navigation Software - Home Page for example.
Reply With Quote Share with Facebook
  #7  
Old 04-03-2010
Senior Member
 
Join Date: Nov 2005
Location: Milton, DE
Posts: 591
Thanks: 2
Thanked 7 Times in 7 Posts
Rep Power: 9
Flybyknight is on a distinguished road
The Nautical Almanac Site Reduction Method is entirely different from HO 229, as is different from Ho 214 as is different from Ageton etc.

Dick
Reply With Quote Share with Facebook
  #8  
Old 04-04-2010
hellosailor's Avatar
Senior Member
 
Join Date: Apr 2006
Posts: 10,372
Thanks: 1
Thanked 72 Times in 70 Posts
Rep Power: 10
hellosailor has a spectacular aura about hellosailor has a spectacular aura about
I'd also vote for software. Even if you don't want to RELY on it, you can use it as a fast reality check. If it disagrees with your hand reduction--you know there's a problem somewhere.

Used Palm IIIxe PDA, $25. John Manson's "Navigation" suite for the Palm, probably another $25. Great little combination and yes, it can be used on older and newer and fancier Palms as well.
Reply With Quote Share with Facebook
  #9  
Old 04-09-2010
Junior Member
 
Join Date: Mar 2010
Location: San Francisco
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
SeppSF is on a distinguished road
Navigation without electronics

Hello All,

Thanks for your great advice. Actually I'm trying to find my position without the use of any electronics. So the tip with HO249 was great. For anybody who is looking for either 249 or 229. Actually the Starpath book is using the HO249 tables, which are SIGHT REDUCTION TABLES FOR AIR NAVIGATION.

I got my 2010 almanac from Amazon. But its kind of from the UK Hydrographic Office. But the Sight Reduction Table are showing different values than the HO ones.

I'll check it out on the weekend. I will try to find this position:
N37.76579, W123.10245. No worries...I'll bring a GPS as well.
Reply With Quote Share with Facebook
  #10  
Old 04-09-2010
AdamLein's Avatar
Senior Member
 
Join Date: Nov 2007
Location: Coquitlam, BC
Posts: 1,866
Thanks: 1
Thanked 0 Times in 0 Posts
Rep Power: 7
AdamLein will become famous soon enough
Quote:
Originally Posted by SeppSF View Post
Actually I'm trying to find my position without the use of any electronics. So the tip with HO249 was great.
A noble goal. You know you can get a slide rule with trigonometric tables?
__________________
s/v Essorant
1972 Catalina 27
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Basic Celestial Concepts Jim Sexton Seamanship Articles 0 06-28-2004 08:00 PM
Working With the Stars—Celestial Navigation Jim Sexton Seamanship Articles 0 05-06-2003 08:00 PM
Working With the Stars—Celestial Navigation Jim Sexton Her Sailnet Articles 0 05-06-2003 08:00 PM
Navigation Basics Jim Sexton Learning to Sail Articles 0 01-04-2002 07:00 PM
Navigation Basics Jim Sexton Her Sailnet Articles 0 01-04-2002 07:00 PM


All times are GMT -4. The time now is 05:25 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012