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-to-star distances
    From: Fred Hebard
    Date: 2004 Sep 30, 08:32 -0400

    On Sep 29, 2004, at 10:57 PM, Alexandre Eremenko wrote:
    
    > Fred,
    > Finally I obtained a relally good measurement for
    > Vega-Arcturus distance!
    >
    > Sept 29, GMT 0h5m:
    > Arcturus-Vega, alt(Arctur)=30d, alt(Vega)=83.
    > Galileo scope, 4x40:
    > SEXT DIST           ERROR
    > 59d06.5'            -0.6'
    > 59d06               -0.1'
    > 59d08.3'            -2.4'
    > 59d06.6'            -0.7'
    > 59d05.8             +0.1'
    > 59d05.7             +0.2'
    > Kepler (inverting) scope 7x30 with cross-hairs:
    > SEXT DIST           ERROR
    > 59d05.8'            +0.1'
    > 59d06.0'            -0.1'
    > 59d05.9'             0.0'
    > 59d05.8'            +0.1
    > 59d05.8             +0.1
    
    > It is interesting: I am somewhat confused because the Russian manual
    > calls the Galileo scope "the night scope" and the inverting one
    > "the day scope". The manual says: "attach the inverting one for Sun
    > observations and the Galileo for night observations.
    
    Alexandre,
    
    That is indeed a good result!  It looks like your sextant is both
    accurate and precise at that angle, which one would expect in a new
    instrument.
    
    One quibble, the inverting scope probably is not 7x30.  The 7 refers to
    the magnification, and the 30 to the diameter of the objective lens in
    millimeters.  I expect your inverting scope probably has a diameter of
    about 15 mm.
    
    The reason the Galilean scope is preferred for star _altitudes_ is that
    it probably has a much larger objective than the inverting scope.  Thus
    it gathers more light, making it easier to see stars at dusk, when the
    horizon is still visible.  For sun shots during the day, the greater
    magnification of the inverting scope makes it more accurate; there's no
    need to admit more light to make the sun visible.
    
    According to Bowditch via Bruce Stark, the inverting scope is preferred
    for lunars, and presumably would be preferred also for star-to-star
    shots.
    
    Hopefully, I will acquire a good 7x scope before long and be able to do
    better with stars and lunars.
    
    Fred
    
    
    

       
    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