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
    Name or NavList Code:
    Email:
       
    Reply
    Re: Instrument Error
    From: Fred Hebard
    Date: 2005 Apr 29, 12:40 -0400

    On Apr 28, 2005, at 3:03 PM, Bill wrote:
    
    >> Fred wrote
    >
    >> Here are the data with the mean date and time, UT1, and the altitudes.
    >> The location was 36*46.8N, 81*50.7W.  The observation for 18 April is
    >> listed as for 17 April in the original table, where the separate dates
    >> are zone time rather than UT1.  Most of the the time the sun and moon
    >> are higher than 20* altitude.
    >
    > Fred
    >
    > Your data does not seem to support my hunch that the error gets greater
    > later in the day.  Must be pilot error on my part.
    >
    > The frustrating part is that the above are representative of other
    > series.
    > Late afternoon series with error STDEV as low as 0.18', but mean of
    > long
    > 27.78 off.  Early afternoon series with error STDEV of 0.36' but mean
    > longitude 3.75' off.
    >
    > Bill
    
    Bill,
    
    Were you always looking at the sun through the clear part of the
    horizon mirror or at it's reflected image?  I generally aim the
    telescope at the lower body, as it's easier to hold the sextant.  If
    you're reversing the body at which the telescope is aimed between early
    and late afternoon, that might account for the difference.
    
    If reversing, part or all of it might be shades.
    
    Whether reversing or not, the gap in late afternoon might be caused by
    not aiming straight and not centering the horizon body on the optical
    axis.  Those sorts of errors always cause the distance to be too great.
    
    The data also suggest more practice is needed, as you know.
    
    Fred
    
    
    

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Get a NavList ID Code

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

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

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

    Email Settings

    NavList ID 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