Welcome to the NavList Message Boards.


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

Compose Your Message

Add Images & Files
    Re: Refraction
    From: Robert Eno
    Date: 2005 Sep 3, 13:38 -0400

    Most bubble sextants will measure negative altitudes. My RAE MK IXA goes as
    low as -13 degrees. My A-10 goes to - 2 degrees 55 minutes. I believe that
    most marine sextants are also capable of measuring negative altitudes to at
    least - 5 degrees.
    A small clarification to my earlier comments regarding refraction in the
    polar regions: your sextant would not yield a negative reading, the
    calculated altitude would be negative. It is only at (height of eye)
    altitudes of several thousand feet asl (as in an aircraft) that one would
    observe a negative altitude.
    ----- Original Message -----
    From: "Fred Hebard" 
    Sent: Thursday, August 04, 2005 12:50 PM
    Subject: Re: Refraction
    > Marcel,
    > OK, I got it.  Ignore my last post.  You might want to look at the
    > Introduction to the Air Almanac, which should give instructions for its
    > use, and should discuss this case.  I've never seen a bubble sextant,
    > so I don't know whether they measure negative altitudes.
    > Fred
    > On Aug 4, 2005, at 12:20 PM, Marcel E. Tschudin wrote:
    >> Yes, how do I get in this? Just trying to cover in a self-made program
    >> the
    >> situation from an object at the horizon (over sea level) as seen from a
    >> mountain or air craft.

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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