Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Star Identification
    From: Greg R_
    Date: 2008 Jul 30, 11:50 -0700

    --- "Greg R."  wrote:
    
    > would have been a lot more problematic back in the "old days"
    > having to do multiple sight reductions (or maybe partial reductions)
    > manually trying to figure out just what it was that you sighted.
    
    I was just thinking about how I'd attack this problem if I had to, and
    it dawned on me that LHA Aries would be known for the time of the
    sight, and calculating the SHA (i.e. working "backwards" from AP Long.
    and LHA) might be a way to identify the star.
    
    But with LHA being dependent on SHA, that's really 2 variables to solve
    for - easy enough to do with a computer or a calculator (i.e. making
    "trial cuts" until the pieces all fit together), but probably a lot
    more work to do the iterations manually.
    
    --
    GregR
    
    
    
    --- "Greg R."  wrote:
    
    >
    > --- Anabasis75@aol.com wrote:
    >
    > > This is correct, except when the cloud cover doesn't cooperate
    > > with the pre-computed stars and you are left shooting whatever you
    > > can see.
    >
    > Agreed... and like you said, it's a lot easier to do these days with
    > computers/calculators/etc. - would have been a lot more problematic
    > back in the "old days" having to do multiple sight reductions (or
    > maybe
    > partial reductions) manually trying to figure out just what it was
    > that
    > you sighted.
    >
    > Also points up how "spoiled" we are in this modern age of instant
    > navigation that's usually accurate to just a few feet, wonder how
    > much
    > patience we'd have if we had to wait a couple (or maybe several) days
    > before getting an accurate position fix.
    >
    > --
    > GregR
    >
    >
    >
    > --- Anabasis75@aol.com wrote:
    >
    >
    > > Greg wrote:
    > >
    > > Usually you'll pre-compute elevations and azimuths of stars
    > *before*
    > > doing the sights, and then point the sextant accordingly (it's
    > > usually
    > > pretty obvious what star you're looking for, just look for  the
    > > brightest object in the sextant's field of view... ;-)).
    > >
    > >
    > > =================
    > >
    > > This is correct, except when the cloud cover doesn't cooperate with
    > > the
    > > pre-computed stars and you are left shooting whatever you can see.
    > I
    > > have  had
    > > this happen several times at sea, when the only stars I could shoot
    > > were  none
    > > of the ones I wanted to shoot.
    > >
    > > To combat this, I recorded the approximate azimuth as well as
    > > altitude.
    > > Fortunately I was still shooting major stars and was able to  find
    > > them on my
    > > star finder.  If they had been minor stars, I probably  would have
    > > taken the easy
    > > way out and just not reduced them (this was all before  I had
    > > computers for
    > > this kind of work).
    > >
    > > JCA
    > >
    > >
    > >
    > > **************Get fantasy football with free live scoring. Sign up
    > > for
    > > FanHouse Fantasy Football today.
    > > (http://www.fanhouse.com/fantasyaffair?ncid=aolspr00050000000020)
    > >
    > > >
    > >
    >
    >
    > >
    >
    
    
    --~--~---------~--~----~------------~-------~--~----~
    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
    To unsubscribe, email NavList-unsubscribe@fer3.com
    -~----------~----~----~----~------~----~------~--~---
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site